Raspberry Pi 2 Server Essentials

Raspberry Pi 2 Server Essentials
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Raspberry Pi 2 Server
Essentials
Transform your Raspberry Pi into a multi-purpose web
server that supports your entire multimedia world with
this practical and accessible tutorial!
Piotr J Kula
BIRMINGHAM - MUMBAI
www.allitebooks.com
Raspberry Pi 2 Server Essentials
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First published: April 2016
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Credits
Author
Project Coordinator
Piotr J Kula
Judie Jose
Reviewers
Proofreader
Ian McAlpine
Safis Editing
Cédric Verstraeten
Indexer
Commissioning Editor
Monica Ajmera Mehta
Priya Singh
Graphics
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About the Author
Piotr J Kula started his passion for computer technologies when he took apart his
father's IBM PC/XT machine at the age of 6. It became clear that Piotr had a natural
ability with technology after he reconstructed the machine, and it booted.
After 25 years, Piotr has worked for various companies in different countries. He has
always solved complex problems or engaged in new experiences. As long as it had a
processor of some sort, Piotr was always the first to try, fix, or configure it.
Today, Piotr is the CEO of his own company, Kula Solution Ltd., in the United
Kingdom. Piotr is certified in several Microsoft technologies, and he specializes in
Microsoft and Linux technologies.
Piotr's dream is for a unified experience between Linux and Microsoft. He has never
been deterred by negativity from either side, and instead, he has strived to find a
way to build a bridge between these distant giants. After discovering Raspberry
Pi, he completely replaced every other embedded device that he owned and was
successful at releasing Raspberry Pi Server Essentials, with Packt Publishing.
Today, Piotr is one step closer to fulfilling his dream with the release of Raspberry Pi
2 Server Essentials. This book is mostly about Linux, but it also talks about integrating
and running Windows on your beloved Raspberry Pi.
I would like to thank Katarzyna Kula, my amazing wife who helps
me decide when enough work, is enough! For always supporting me
through all my projects and countless hours spent on my computers.
I would also like to thank the entire Raspberry Pi community,
especially the members on Stack Exchange, everybody at Packt
Publishing, and those who helped me in various ways to complete
this book.
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About the Reviewers
Ian McAlpine's first introduction to computers was his school's Research Machines
RML-380Z and his Physics teacher's Compukit UK101. This was followed by a
Sinclair ZX81 and then a BBC Micro Model A, which he still has. This interest resulted
in a MEng in Electronic Systems Engineering from Aston University and an MSc in
Information Technology from the University of Liverpool. Ian is currently a product
expert in the BI & Analytics Competency Centre, at SAP Labs, in Vancouver, Canada.
The introduction of Raspberry Pi not only rekindled his desire to tinker but also
provided an opportunity to give back to the community. Consequently, Ian was a
very active volunteer working on The MagPi, a monthly magazine for Raspberry Pi,
which you can read online or download for free from https://www.raspberrypi.
org/magpi. He also holds an amateur radio license (callsign VE7FTO) and is a
communications volunteer for his local community Emergency Management Office.
He was a technical reviewer for the Raspberry Pi Cookbook for Python Programmers and
Raspberry Pi Projects for Kids books, both published by Packt Publishing.
I would like to thank my darling wife, Louise, and my awesome kids
Emily and Molly for allowing me to disappear into my "office"… and
for training our dog to fetch me!
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Cédric Verstraeten is an MSc in Engineering who's primarily active in the C++
community. He works as a software engineer and is a huge open source enthusiast.
He spends most of his time on side projects that can automate and simplify people's
lives. He's the organizer of the Raspberry Pi Belgium meetup and the founder of the
Open Source video surveillance system called Kerberos.io.
I would like to thank Packt Publishing for allowing me to be part
of this as a reviewer. I really think their books can give people an
in-depth overview of a particular topic.
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Table of Contents
Prefaceix
Chapter 1: Getting Started with the Raspberry Pi
1
Hardware requirements
Power supply
USB hub
SD cards
Extra peripherals
Essential peripherals
Useful peripherals
1
2
3
4
4
5
5
Internet 3G dongles
Audio recording
Other media add-ons
Fun peripherals
Installing Raspbian on the Raspberry Pi
Understanding the design of the Raspberry Pi
Boot process
Other capabilities
Hardware limitations
5
6
6
7
8
9
10
10
11
Network speeds
11
USB bottlenecks
11
Time12
References12
Summary13
Chapter 2: Preparing a Network
15
Local Area Network (LAN)
The eth0 port
The wlan0 interface
The loopback (LO) interface
15
16
17
17
[i]
www.allitebooks.com
Table of Contents
A wireless configuration (Wi-Fi)
Recommended wireless adapters
Setting up from a desktop
Setting up from a console
Using wicd-curses
A static network address
Testing and benchmarking your network
Basic tests
Advanced benchmarking tools
17
17
18
18
21
22
23
23
24
A speedtest application
24
iPerf25
Recommended bandwidth
25
Internet configurations
26
Home packages
27
Business packages
27
Dynamic DNS
28
Installing a client
28
The free Dynamic DNS domain workaround
29
Summary30
Chapter 3: Configuring Extra Features
31
Chapter 4: Using Fast Web Servers and Databases
39
Updating Raspberry Pi
31
Updating the firmware
32
Updating packages
32
Updating distribution
32
Outcomes33
Hardware watchdog
33
Enabling the watchdog and daemon
34
Testing the watchdog
35
Enabling extra decoders
35
Buying licenses
35
MPEG-236
VC-136
Hardware monitoring
36
Summary
37
Apache versus nginx versus Kestrel
Installing nginx
Configuring the nginx virtual hosts
Extra frameworks for nginx
Python API
Executing Python
[ ii ]
39
40
41
43
43
43
Table of Contents
Node.js45
Installing Node.js
What is NPM
The Node.js server
45
46
46
.NET and ASP.MVC
48
Prerequisites for .NET 5
Installing DNVM, DNU and DNX
Installing DNX
Running the MVC website
MVC and nginx
Other .NET applications
49
50
50
50
52
52
Installing PHP
53
Installing a database
54
Installing MySQL
54
Installing phpMyAdmin
55
Installing SQLite
56
Summary58
Chapter 5: Setting Up the Raspberry Pi as a File Server
Connecting the external storage
Preparing the storage medium
Listing the available drives
Formatting a drive
Creating a EXT4 partition
Mounting the drives
Remounting a disk after reboot
Accessing files
The FTP service
Connecting with FileZilla
Connecting with WinSCP
59
59
60
60
61
62
62
63
63
63
64
64
The Samba service
Installing and configuring Samba
Network shares
AFP for Macintosh
Installing and configuring Netatalk
Shares and Time Machine
BitTorrent Sync
Installing BTSync 2
The hardware RAID
Configuration
Massive storage
Redundant storage
Summary
65
65
66
67
67
68
68
68
70
70
71
72
72
[ iii ]
Table of Contents
Chapter 6: Setting Up Game Servers
Updating to Jessie
Selective settings
Game servers
OpenTTD
Installing OpenTTD
Configuring OpenTTD
Playing OpenTTD
Freeciv
Installing Freeciv
Configuring Freeciv
Playing Freeciv
OpenArena
Installing OpenArena
Configuring OpenArena
Playing OpenArena
73
73
73
74
74
75
75
75
76
76
76
77
77
77
77
78
Minecraft
78
Installing the Java Hard-Float
78
Installing the Minecraft server
79
Configuring Minecraft
79
Playing Minecraft
80
Summary80
Chapter 7: Streaming Live HD Video
81
Installing UV4L
81
Configuring the UV4L-RaspiCAM
82
Installing WebRTC
83
WebRTC streaming
83
Real time HTTP streaming
84
Web conferencing
85
Streaming the X desktop
86
Text overlay
87
Object detection and tracking
88
Removing the overlay watermark
88
The HUD sample
88
Using the overlay binary
89
Inline variables
89
Compiling the overlay code yourself
90
Summary91
[ iv ]
Table of Contents
Chapter 8: Setting Up the Pi as a Media Center Server
93
Slideshows93
Using fbi
94
Playing videos
94
OMXPlayer for video playback
95
Playing audio
95
Aplay for audio playback
95
OMXPlayer for audio playback
95
Using AirPlayer
96
Using alsamixer
96
Installing OSMC
96
Configuring OSMC
97
Enabling other codecs
97
Wireless configuration
97
Media sources
98
Using add-ons
98
AirPlay98
Enabling CEC and remotes
99
Performance optimization
99
Overclocking99
Summary99
Chapter 9: Running Your Pi from a Battery's Power Source
Hardware requirements
Charging stations
Battery packs
Voltage regulator
Ohm's Law
Discharge curves
Discharge characteristics
101
101
102
103
104
106
106
107
Putting it all together
107
How long will it last?
107
Summary108
Chapter 10: Windows IoT Core
109
Getting started
Flashing IoT
110
110
Python for Linux or Windows 7 and 8
110
The first boot
Remote connections
Visual Studio (VS)
Installing Visual Studio 2015
The Hello World application
111
112
112
112
113
[v]
Table of Contents
Deploying the application
116
Debugging116
Breakpoints117
Unhandled exceptions
118
Samples119
Windows 10 IoT WebGUI
119
Setting up the startup app
119
Peripherals120
Bluetooth120
Wireless120
Summary120
Chapter 11: Running Your ownCloud
121
Installation121
Requirements121
MySQL122
nginx and PHP
122
Permissions126
The first configuration
The admin configuration
The server admin
Installing apps
126
128
128
129
Calendar130
Other apps
130
Daily functionality
131
The World Wide Access
131
Summary131
Chapter 12: The Internet of Things – Sensors in the Cloud
133
What is IoT?
134
Ohm's law
134
How much power?
135
Choosing sensors
137
Resistors, fuses, and diodes
137
Transistors138
Integrated Circuit Packages
140
Putting it all together
141
Accurate data using Arduino
141
Building a weather station
142
Real-time embedded devices
142
The data communication
142
Real-time events
142
[ vi ]
Table of Contents
Analog inputs
143
Parts required
143
Storing data on the Cloud
143
Phant144
Summary144
Index145
[ vii ]
Preface
The purpose of this book is to get you started with Raspberry Pi, but this book has
chapters focused on Raspberry Pi 2. The main goal here is to get your projects started
with some solid hardware and programming tips, which are essential.
What this book covers
Chapter 1, Getting Started with the Raspberry Pi, will cover the basic equipment that we
need to use with this book. We will have to look into other peripherals that we have
bought to see how the Raspberry works. We will then see how to flash the newest
Raspbian image to our SD card.
Chapter 2, Preparing a Network, will illustrate how to set up LAN and a wireless
connection to our network to connect to the Internet. We will set some network
benchmarks and understand some of its limitations. We will also look into Dynamic
DNS hosting.
Chapter 3, Configuring Extra Features, will illustrate how to update the software and
firmware of Raspberry Pi. You will learn about the watchdog and understand how to
buy extra decoder licenses.
Chapter 4, Using Fast Web Servers and Databases, will illustrate how to set up a quick
web server using nginx with PHP, and we can decide whether we want to use
MySQL or SQLite.
Chapter 5, Setting Up the Raspberry Pi as a File Server, will illustrate how to attach
and format a USB storage medium. We will not only look into the various ways of
sending data to Raspberry Pi, but we will also understand how to share media on the
network. As an extra task, we will look into creating the hardware RAID!
[ ix ]
Preface
Chapter 6, Setting Up Game Servers, will explore open source game engines that are
available on the repository. We will also have a sneak peek at the Jessie repository,
which is in beta testing.
Chapter 7, Streaming Live HD Video, will explore the camera module and illustrate
a simple technique to stream a video. This chapter contains exclusive streaming
tutorials.
Chapter 8, Setting Up the Pi as a Media Center Server, will illustrate how to connect an HD
monitor and play some videos that were recorded or stored earlier. We will also look
into OSMC, and we will explore the benefits of running it as a dedicated media player.
Chapter 9, Running Your Pi from a Battery's Power Source, will explain the benefits of
various types of battery technology and how to get the best performance without
spending too much money.
Chapter 10, Windows IoT Core, is finally available on the embedded ARM, and it
will explore the capabilities of running IoT as an Operating System with a basic
programming tutorial with C#.
Chapter 11, Running Your ownCloud, will discuss how to install the ownCloud
software on your Pi, and it will free you from privately owned services.
Chapter 12, The Internet of Things – Sensors in the Cloud, is more of a case study about how
to complete your projects by storing accurate data accessible anywhere in the cloud.
What you need for this book
You need at least a Raspberry Pi 2 with a recommended 8 GB SD card, 1 amp micro
USB power supply, and a network cable connected to a router with the Internet.
Who this book is for
Seeking inspiration for some new tech projects? Want to get more from your
Raspberry Pi? This book has been created especially for you!
Conventions
In this book, you will find a number of text styles that distinguish between different
kinds of information. Here are some examples of these styles and an explanation of
their meaning.
[x]
Preface
Code words in text, database table names, folder names, filenames, file extensions,
pathnames, dummy URLs, user input, and Twitter handles are shown as follows:
"We can include other contexts through the use of the include directive."
A block of code is set as follows:
auto lo
iface lo inet loopback
iface eth0 inet dhcp
When we wish to draw your attention to a particular part of a code block, the
relevant lines or items are set in bold:
allow-hotplug wlan0
auto wlan0
iface wlan0 inet dhcp
Any command-line input or output is written as follows:
sudo touch wpa_supplication.conf
nano wpa_supplication.conf
New terms and important words are shown in bold. Words that you see on the
screen, for example, in menus or dialog boxes, appear in the text like this: "Clicking
the Next button moves you to the next screen."
Warnings or important notes appear in a box like this.
Tips and tricks appear like this.
Reader feedback
Feedback from our readers is always welcome. Let us know what you think about
this book—what you liked or disliked. Reader feedback is important for us as it helps
us develop titles that you will really get the most out of.
To send us general feedback, simply e-mail [email protected], and mention
the book's title in the subject of your message.
[ xi ]
Preface
If there is a topic that you have expertise in and you are interested in either writing
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[ xii ]
Preface
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Questions
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[ xiii ]
Getting Started with the
Raspberry Pi
Connecting to a network should be as easy as plugging in a cable. The question
is, what can we do on the Raspberry Pi after we are connected to the Internet or a
local network? This is why it is essential to learn about the hardware prerequisites
and capabilities of the Raspberry Pi, so that your idea is theoretically possible to
accomplish. Also, knowing your hardware inside out will make troubleshooting
problems much easier to deal with later in the book.
The most common problems associated with the Raspberry Pi are related to power.
These problems can cause it to restart, cause unexpected behavior, or may show a
rainbow screen during the boot process if you have an external monitor connected.
This chapter is all about identifying your Raspberry Pi and the peripherals that you
are using or may want to use along with it. There are two main pieces of information
you should know about your Raspberry Pi: the model and version.
Hardware requirements
This book assumes that you are using a Raspberry Pi 2, Model B.
The Raspberry Pi 2 is mostly backwards compatible with all its predecessors.
Whenever a compatibility issue occurs, it will be made clear to the user and an
alternative solution will be provided, if possible.
The latest versions of Raspberry Pi at the most basic level only need a power supply
and Micro SD card to run. To make initial configurations easier, it is recommended
that you also have an HDMI cable, a wide screen monitor or television with HDMI
input, an Ethernet cable, and a USB keyboard.
[1]
Getting Started with the Raspberry Pi
The following table describes the main differences between the various models:
Model
Generation 2 Model B
Model B+
Soc
Model A+
BCM2836
BCM2835
CPU
900 MHz Quad Core ARMv7
700 MHz single core ARMv6
GPU
VideoCore IV @ 250Mhz / OpenGL ES 2.0 / H.264/MPEG-4 AVC
SDRAM
1 GB
512 MB
256 MB
USB
4
2
1
Audio in
No direct input and two revision boards via I2S, all of which use a USB
Network
10/100 Mbit/s
GPIO
17
17
17
Header
40 pins
26 pins
26 pins
Power
800 mA (4.0 W)
800 mA (4.0 W)
200 mA (1 W)
SD card
Micro SD slot
None
With the latest models of the Raspberry Pi, most peripherals should work out of the
box, as these versions have been upgraded with a dedicated power circuit to handle
peak loads but also reduce overall power consumption. Only the plus models have
this new circuit, and all the older versions of Raspberry Pi might suffer from power
problems caused by inefficient circuits. The most power-efficient Raspberry Pi is
Model A+ and is commonly powered using batteries. We will discuss powering your
Raspberry Pi from batteries in a later chapter of this book.
Power supply
The Raspberry Pi 2 should ideally be powered using a 2 amp USB power supply
if you plan to connect peripherals to the USB ports. The most common power
supplies found at home are 1 amp power supplies, which are typically supplied with
smartphones, tablets, or mini computers. These chargers are usually made from good
quality components and can easily handle the stress of additional power, power
spikes, and produce a clean DC power source, which is very important for Wi-Fi or
serial peripherals.
You should also pay attention to the USB cable that you are using as some cables are
produced cheaply and the copper wire inside them is very thin, which struggles to
deliver 1 amp or more of current when needed.
[2]
Chapter 1
In an independent test, the best USB charger turned out to be the HP TouchPad
charger (P/N 157-10157-00), and the next best ones are Apple A1265, Apple iPad
A1357, and Samsung Cube ETA0U80JBE. They are considered to be the best because
they produce very clean DC power and can handle peak loads for extended periods
of time. Be careful, though, as a lot of counterfeit chargers are also being sold now,
especially Apple A1265. As time passes, some of these power supplies may become
obsolete. Try and search for newer tests.
To help visualize the DC noise problem, examine the following image. The
waveform on the left-hand side is extremely noisy and will cause serious problems
for communication peripherals such as Wi-Fi, bluetooth, or even serial. The
waveform on the right-hand side is considered to be clean and stable:
Search the Internet for tips on how to identify
counterfeit chargers.
USB hub
When you purchase a powered USB hub, it is usually supplied with a 2 or 3 amp
power supply. This is enough to power USB devices such as a Wi-Fi adapter, a USB
hard drive, a few other peripherals, and even the Raspberry Pi itself.
A typical problem occurs with HD USB cameras where the picture goes black after
a running for some time. Using a powered USB hub will solve this problem.
[3]
Getting Started with the Raspberry Pi
SD cards
SD cards all look alike, but, in fact, some use a multitude of different controllers and
NAND Flash memory chips. All these combinations make up the reliability and
speed of the card; the cheapest is the worst, usually. That said, spending a fortune
on an SD card is not a good idea either. The speeds of SD cards are marked with a
numeric symbol ranging from 1, the slowest, to 10, the fastest. A class 6 or 8 SD card
is a good balance between performance and price.
However, not all Class 10 cards are the best choice either. The only way to be sure
is to use a trusted speed test application to verify that the card is performing at the
advertised read and write speeds; this is the best way to identify counterfeit cards:
The SD card should only act as the primary partition for an operating system and
applications installed on it. Using an SD card for frequently changing data, such as
databases, is not a good idea as it degrades the life of the card faster than expected.
Instead, we should use external storage devices, such as hard drives or Network
Attached Storage (NAS), to handle frequently changing data but also help with
storing large amounts of media.
This book assumes that you are using at least an 8 GB SD card.
Extra peripherals
The Raspberry Pi is branded as a computer, and it is expected that we can connect
various different devices to it. Raspbian is based on Debian, and an immense effort
has been made to port the majority of drivers and software available for Raspbian.
You might have some old USB peripherals lying around, for example, a joystick. If
you can find a driver for any other Linux platform, it should be possible to make
it work with Raspbian. Plug it in, use the lsusb command-line utility, and check
whether it has been detected. If you manage to get it working with your knowledge,
you should share this knowledge on a forum for the benefit of other users.
[4]
Chapter 1
Essential peripherals
You should consider buying these peripherals and dedicating them for the use of
your Raspberry Pi. They will really make it easier to set everything up and are even
used for long-term purposes:
• Wireless USB network adapters: At the time of writing this book, the current
Raspbian image supports a variety of wireless adapters without the need
to install any extra drivers. Many of the mini, nano, or micro versions run
directly from the Pi's USB ports and do not require a powered USB hub.
• USB hubs: Because some versions of the Raspberry Pi are limited to two USB
ports, it might be wise to have a compatible, powered USB hub. Powered is
the key word here, as this will allow you to plug in any USB device or several
devices at the same time without affecting the Pi's power stability. At the time
of writing this, Raspbian is not fully compatible with three USB hubs yet.
• Keyboards and mice: Most wired keyboards and mice will run directly
off the Raspberry Pi USB port. Many Bluetooth keyboards and mice also
work directly off the Pi's USB ports but require initial setup using a wired
keyboard. Some wireless keyboards, such as the Microsoft 3000 series, do not
need any configuration as the USB dongle emulates a PS/2 wired keyboard
and can be used straight away at boot time without any extra configuration.
You can visit http://elinux.org/RPi_VerifiedPeripherals
for an up-to-date list of compatible peripherals.
Useful peripherals
As you grow more familiar with your Raspberry Pi, you will think of new a bigger
ideas for your projects. With such ideas, you might need a few more useful devices
to help you out.
Internet 3G dongles
You can connect to the Internet using a 3G dongle. These require a lot of power and
will need to run from a powered hub to operate at full speed. They are a really easy
way to connect your Raspberry Pi to the Internet even in the most remote places of
your country. As long as you have a basic voice signal, you should always be able to
use GPRS (single channel 57.5 kbps or dual channel 115 kbps), which can be enough
to send plenty of logging text data. Some countries offer free text messages, and this
can also be used to send and receive the bare minimum of data. If you plan to run
a server, it would be recommended that you use LAN or Wi-Fi connected to
an ADSL/DSL connection instead.
[5]
Getting Started with the Raspberry Pi
Audio recording
The Raspberry Pi has its own sound output hardware, which is really good at giving
you a high definition sound over HDMI or analog audio via the 3.5 mm jack.
You might find yourself in a situation where you would like to record audio from a
line input or microphone; you could then use any USB 1.1 or USB 2.0 sound capture
device to do this.
Other media add-ons
• IR receivers: Infrared (IR) receivers are a great way to control your
Raspberry Pi using conventional remote controls. The FLIRC USB IR remote
dongle is a great way for you to start doing this.
• TV and radio receivers: This is the ultimate way to turn your Raspberry Pi
into a full DVR system. Record, playback, or pause live TV from HD satellite
or digital TV. You can listen to your favorite radio channels too.
• Webcams: The Raspberry Pi has a port for its own dedicated HD camera
module. Owning one of these cameras is a real treat, and the latest versions
of Raspbian support UV4L (Video for Linux). A variety of USB webcams are
also supported and support UV4L. Once a fairly complicated task, it has now
become a lot easier to work with.
• Multicard readers: These come in handy if you work with various card
types. Support is limited on generic types, but the USB 3.0 USRobotics all-inone card works really well, and you can mount all six cards at the same time.
• Alamode: WyoLum is a start-up business that creates useful add-ons for
various applications. Specifically, AlaMode is an Arduino-compatible board
with a real-time clock and microSD slot that sits on top of the Raspberry
Pi. You can communicate with Arduino using the Pi's dedicated UART
(Universal Asynchronous Receiver/Transmitter), and it can run off the Pi's
power source. If you like electronic projects and are already familiar with
Arduino, this is worth looking at. You can even use it to flash other Arduinocompatible chips or upload firmware to run on its own!
• HDMI to VGA: If you use an older or spare monitor, television, or LCD
screen that only works with VGA, you can purchase an inline HDMI to VGA
converter from your favorite online auction shops or electronic stores. You
must make sure to buy an active converter, which is slightly more expensive
than a passive convertor. Active means that it contains a microcontroller that
uses power from the HDMI port to convert the digital signal into the VGA
standard. The Raspberry Pi is capable of powering this type of device.
[6]
Chapter 1
Fun peripherals
You might have some of these lying around in your gadget box. Hopefully, reading
about some of these less used devices might spark some creative ideas:
• Joysticks: Microsoft's Xbox 360 controller works like a mouse in X using
xboxdrv, which can be installed from the package repository. Other joysticks
might need a ported driver that can be found on Internet forums.
• USB to SATA: You can purchase simple USB to SATA controllers that allow
you to attach SATA hard drives using dedicated power supplies. The real
fun begins when you use hardware RAID-based USB to SATA controllers
that can be chained in various configurations, which can give you massive
storage, high redundancy, or maximum performance.
Be careful, though, as the maximum throughput speed you
can achieve is governed by the bandwidth of USB 2.0. In
theory, this is a maximum speed of 60 MBps, but is shared
by all the devices on the controller and not per port. There
is more information about this later in the book.
• CAN bus: The CAN bus is the standard used in all modern motor vehicles.
It is a standard port that gives mandatory data that can be interpreted by
anybody, for example, throttle value, misfiring of cylinders, or air to fuel
ratio. PEAK-System has a variety of peripherals and software that are
compatible with the Raspberry Pi. If you have access to manufacturer-specific
codes, you can even adjust engine mappings with these tools.
Adjusting non-standard values may damage your ECU
and will void any warranties.
• Home automation: A compatible device called TellStick runs well as a thirdparty, home automation device for the Raspberry Pi, but as an advanced
Linux user, you should strive to make your own applications using real-time
microcontrollers, such as Arduino on AlaMode, or the very cheap PICAXE
microcontrollers.
• USB missile launcher: Available on a variety of websites and stores, this
is the perfect gadget if you need to shoot plushy missiles at unidentified
objects! This is purely an entertainment peripheral, but you could use it for
DIY projects as well.
[7]
www.allitebooks.com
Getting Started with the Raspberry Pi
• Fingerprint scanners: Futronic's fingerprint scanners work well with
Raspbian, and there are many examples that can be found online. They
are standalone programmable devices that communicate with the Pi using
simple messages over USB-UART and have extensive documentation
available with the device.
• Weather station: Sparkfun sell a pretty complete weather station that
includes a wind vane, anemometer, and tipping bucket rain gauge. The kit
includes clamps and mounting masts. You can add a light, temperature,
and humidity sensor easily and without breaking the bank. The challenge
depends on using a real-time microcontroller and building your own
database to log all the data. But don't worry, there are many tutorials online
that will help you progress further.
Installing Raspbian on the Raspberry Pi
There are many distributions that can run on the Pi. Some are specific real-time
operating systems, such as RISCOS, or mainstream operating systems, such as
Raspbian or Archlinux. A few flavors of home media centers, such as OpenElec or
OSMC (previously known as XBMC). As of June 2015, you will also be able to install
Windows 10 Internet of Things. No Android support is foreseen for the near future.
The Raspberry Pi Foundation recommends that you use their image called NOOBS
(New Out Of Box Software,) which contains frequently updated list of different
operating systems. In this book, we will be using Raspbian. It is supported by the
Foundation and has the best compatibility with ease of use. Raspbian is based on
Debian and is similar to many other Linux operating systems. The steps for installing
Raspbian are as follows:
1. For Windows and Macintosh users, it is recommended by the Raspberry Pi
Foundation that you use the SD Formatter from http://www.sdcard.org/.
For Windows, perform the following steps:
1. Install the SD card formatting tool.
2. Set the Format size adjustment option to ON in the Option menu.
3. Make sure you've selected the correct SD card.
4. Click on the Format button.
For Macintosh, perform the following steps:
1. Install the SD card formatting tool.
2. Select Overwrite Format.
[8]
Chapter 1
3. Make sure you've selected the correct SD card.
4. Click on the Format button.
For Linux, perform the following steps:
1. It is recommended that you use the GParted or Parted tool in Linux.
2. Format the entire disk as FAT.
2. You should download the latest NOOBS archive from
http://www.raspberrypi.org/downloads/
3. Unzip the archive.
4. Copy the extracted files onto the formatted SD card.
5. Insert the SD card into the Raspberry Pi. Plug in your HDMI or other video
cable with a compatible keyboard and power it up.
6. The Pi will boot up and present the list of operating systems; select
Raspbian.
7. If your display is blank, try to press the numeric keys, as listed here, while
the Pi is booted up:
°°
1: HDMI mode
°°
2: HDMI safe mode
°°
3: Composite PAL
°°
4: Composite NTSC
Understanding the design of the
Raspberry Pi
The Raspberry Pi has two identifiable microchips on the PCB:
• In the center is one that's clearly marked with a Broadcom logo and text
starting with BCM283x, which is the main processor
• The Raspberry Pi 2 has its RAM chip at the back of the PCB.
• Near the USB port, there is a smaller chip that is either a USB hub or a USB/
LAN chip, depending on the model.
BCM283x is actually a high-performance GPU with an embedded ARM processor. It
is a SoC (System on Chip), which means that there is small amount of space for code
that executes when it gets turned on. This is known as Stage 1 in the boot process.
[9]
Getting Started with the Raspberry Pi
Boot process
Some network actions need to be performed during the boot process, and it is good
to understand the various stages in case you need to troubleshoot something. The
boot process is as follows:
1. Stage 1 begins on the GPU and executes the code SoC firmware, which starts
to load Stage 2 code to the L2 cache.
2. Stage 2 reads bootcode.bin from the SD card. It initializes SDRAM
(synchronous dynamic random access memory) and loads Stage 3.
3. Stage 3 is the loader.bin file. This loads start.elf, which starts the GPU.
4. During start.elf, it prepares to load kernel.img.
5. The kernel image then reads config.txt, cmdline.txt, and bcm283x.dtb.
6. If the .dtb file exists, it is loaded at 0 × 100, and the kernel is loaded at 0 ×
8000 in memory.
7. The kernel image is the first binary that runs on the ARM CPU, and it can be
compiled with custom support for specific hardware.
8. The operating system starts to load.
All the source code in stages 1 to 3 are closed source and protected by Broadcom.
These closed source files are compiled and released by Broadcom only; you can
update them on your SD card by running a firmware upgrade in Raspbian, which is
covered later.
The kernel.img file connects the application to the hardware. Any computer with
an operating system has a kernel of some sort. In Linux, it is possible to compile your
own kernel, and it might be the first file that you might want to amend yourself. This
allows you to change the boot screen, load custom drivers, or perform other tasks
that you might need. This is an advanced task and is not covered in this book.
Other capabilities
BCM283x also has dedicated audio hardware together with video encoding/decoding.
This allows the Raspberry Pi to playback HD (MPEG-4) content, such as videos, or
render games using OpenGL ES. You can buy additional encoder/decoder licenses for
extra functionality, such as MPEG-2, used in DVD video encoding and VC-1, which is
used by Microsoft's WMV formats. This is also used for Silverlight live streaming.
The SD card is also directly interfaced by the Broadcom chip using dedicated
hardware inputs/outputs and interrupts.
[ 10 ]
Chapter 1
All that dedicated hardware means that while those sections of the chip are fully
utilized, the ARM CPU will be idle or hardly used. This allows you to compute other
transactions synchronously, and this is what makes the Raspberry Pi a truly unique
single board, credit card-sized computer!
Hardware limitations
All this hardware that is crammed into one tiny space has its drawbacks. Some are
deliberate and others are not. You should consider that these are theoretical calculations;
real-world performance may vary, but are usually slower than theoretically estimated.
Network speeds
It may be disappointing that the Raspberry Pi Foundation decided to use a 100 Mbps
LAN chip instead of a gigabit one. We need to crunch some numbers to justify this
decision, though. Let's convert megabits to a more familiar megabytes. To get to
megabytes per second from megabits per second, we divide 100 Mbps by 8 (there are eight
bits in a byte). This equates to 12.5 megabytes per second at 100% LAN capacity. For a
single user, this is only roughly 20% of what the USB hub can handle. This means that
by design, this is an unchangeable bandwidth limitation for networking.
If you plan to share files with several users at the same time, each new user
will bump down the other user's bandwidth to accommodate their own. As a
workaround, you could add a USB gigabit LAN peripheral. But due to speed
constraints of the USB hub, you will only use approximately 48% of the gigabit LAN.
To make matters worse, any hard drives running on the USB port will start to fight
for bandwidth. The USB controller has to share 480 Mbps across all ports! One port
is used by the 100 Mbit network card, and the other connects the hub to the GPU.
For one user, this means a maximum bandwidth of 240 Mbps. Why 240 Mbps? This
is because 240 Mbps goes to the LAN and 240 Mbps goes to the hard drive, and
theoretically, there is no USB bandwidth left for anything else.
This could be a problem for a multiuser environment, but for home use, you would
not run into any major problems as the bandwidth can accommodate HD video
streams while serving other clients. This is why the cheaper 100 Mbps version
was used.
USB bottlenecks
As it was made clear by the bottlenecks found in the LAN, the worst thing about
USB bottlenecks is that there is no way to work around this problem! This is because
the USB controller connects to the Broadcom and LAN chips, respectively, on the
PCB without any possibility of expanding or bypassing this chip.
[ 11 ]
Getting Started with the Raspberry Pi
Time
The Raspberry Pi also does not come with a real-time clock, so timekeeping is left to
Internet-based time servers. For many people, this might not cause a problem, but
if you wanted to create a remote, disconnected device that depends on recording
events at various times of the day, you might be left a little bit disappointed.
One easy and reliable way to do this is to connect a USB or I2C RTC that runs off a
small battery. There is an easier and free option, though, but it is not as accurate; you
may want to install the fake-hwclock package. All you need to do is set the time
once, and the software will keep the track of time using a file. If you have a power
outage, the software will read the file and set the time back to the last known time.
The drawback is that you lose that time as there is no way to determine how long the
outage lasted for.
To get time without using the Internet, you can find a cheap GPS receiver. When
the GPS gets a good lock, it will provide you with extremely accurate time. This
same method is used to synchronize GSM voice calls on mobile phone technologies
across the world.
Another method is to use the time broadcasted by long wave radio signals. These
also broadcast extremely accurate time using atomic clocks. The availability depends
on your location, though. These are currently available in Colorado for most of the
US; Germany, Russia, the UK for Europe; and finally, Japan. The radio waves operate
on different frequencies and more research is required for this method.
References
The following are the references for this chapter:
• Visit for more information on the USB power benchmark http://www.
righto.com/2012/10/a-dozen-usb-chargers-in-lab-apple-is.html.
• Crystal Disk Mark is a great SD card benchmarking tool with a lot of test
results available online for comparison.
[ 12 ]
Chapter 1
Summary
One of the most popular questions found on the Internet was how to increase the
Pi's performance! With the release of the Generation 2, ARM V7, quad core 900 MHz,
this is no longer the case. At the time of writing this book, one of the most popular
questions is how to run the Raspberry Pi using batteries, which we will cover in a
later chapter!
The purpose of understanding the architecture is vital to a successful long term
project. The Raspberry Pi works like any other computer, but it was designed
purely for experimental and learning purposes. It should not be used in production
environments, but it is an extremely attractive solution for production nevertheless.
It is an excellent platform to share media between friends at school; it is fantastic
to stream HD media on your TV and is robust enough for many standalone
applications.
In the next chapter, you learn how to set up networks on the Raspberry Pi.
[ 13 ]
Preparing a Network
It is important to learn how your network works, especially if you plan to connect
your Raspberry Pi to the Internet. A home user will typically use an Internet package
designed to browse websites and read e-mails. Business packages, on the other hand,
need to do a lot more than you think. These two different ISP packages usually carry
important technical differences that dictate how your network can be reached.
In this chapter, you will learn how to connect to the Internet and look at how to solve
some common problems for home users. You will also learn how to benchmark your
network and try to isolate any network-related issues.
Local Area Network (LAN)
Using the standard Raspbian package, both essential and non-essential drivers are
included. All essential drivers are loaded and some non-essential ones are as well.
We will start by plugging in a network cable between the Raspberry Pi and the
router provided by your ISP. By default, your router has a DHCP server that
automatically assigns an IP address to your Raspberry Pi.
You may also use network switches to make a more complex network but because
the Raspberry Pi has a 100 megabit network port, it may downgrade your entire
network to 100 megabits. Some switches can negotiate separate connections to lower
speed interfaces without downgrading the entire network, but you need to consult
the specifications of the device in order to do this.
[ 15 ]
Preparing a Network
To check whether your LAN is up and running, just type ifconfig, and you will get
text containing your current settings:
Let's try to understand the different keywords from the preceding output:
• HWaddr: This is your Pi's MAC address, which identifies a vendor and
should ideally provide a globally unique address.
• inet addr: This is your current LAN IP address, which belongs to a private
range of either 10.x.y.z (Class A), 172.16.y.x (Class B), or 192.168.x.x
(Class C). They are known as private addresses because they do not exist on
the Internet.
• Bcast: This is a reserved address that's calculated by your network mask, and
it transmits global messages within your private network.
• Mask: This is used in all networks but should only be concerned with
advanced configurations. Masks divide a network into subnet works and
depend on the class your network belongs to.
• inet6 addr: This is your IPv6 address. It will show only if your router
supports this, but it is more difficult to remember.
• RX: This shows how many packets have been received.
• TX: This shows how many packets have been sent.
The eth0 port
The Raspberry Pi will typically use eth0 as its on-board LAN interface. If you
add USB LAN devices, they will have an incremented number after eth; this will
increment the interface number.
[ 16 ]
Chapter 2
The wlan0 interface
When we add a wireless adapter, ifconfig will represent these interfaces using
wlan instead of the eth prefix. All the details are the same, but it helps to visually
identify wired networks from wireless ones.
The loopback (LO) interface
This is known as the home address because it refers to the local device and has a
reserved range starting from 127.0.0.1 and ending at 127.255.255.254. This is a
virtual interface that bypasses local hardware interfaces and rules. It is commonly
used for security reasons and during software testing. For example, you may only
allow the root access of MySQL to a localhost (this will include 127.0.0.1 for
IPv4 or ::1 for IPv6). This means that only the user or service on the computer
will be granted access to this resource. It is reserved, and neither the localhost nor
127.x.y.z can be assigned to users on the Internet.
A wireless configuration (Wi-Fi)
Wi-Fi is a convenient way to allow your Raspberry Pi to operate in a wireless
environment within a wireless network. It is not an ideal solution for servers,
though, as there is an increased latency in transmitting data, and many Wi-Fi
networks suffer from noise generated by other networks on the same frequency.
There are many types of wireless adapter available, and not all drivers are included
with Raspbian. You might have to install a specific driver, but this is usually a simple
process. When talking about wireless configuration, you have to target the chip that
is used on the adapter and not the end vendor who is selling it.
Recommended wireless adapters
One of the most stable and affordable chipsets is Realtek RT8191, which works with
the 802.11n standard. It is also compatible with the older 802.11b/g specifications,
just in case your router does not support the newer 802.11n specification. However, it
does not support 5 GHz frequencies or the 40 MHz dual band.
There is a comprehensive list of compatible adapters available
at http://elinux.org/RPi_USB_Wi-Fi_Adapters.
[ 17 ]
Preparing a Network
Shop around to find the best price, and it's best to not go for overpriced adapters that
claim to be the only and the best ones for your Raspberry Pi.
You should be aware that, by default, wireless and wired
networks do not work in combined mode. After configuring
Wi-Fi you will need to remove your wired connection and reboot
the Raspberry Pi. This will configure the wireless interface
correctly. Connecting the wired connection usually drops the
wireless connection after the Raspberry Pi has been booted.
Setting up from a desktop
Using the Wi-Fi configuration tool found in the menu bar while you're on the
desktop is the most convenient way to connect to your wireless within seconds. It is
recommended that you start with this if you have just installed Raspbian and plan
on using Wi-Fi instead of an Ethernet connection. Your SSID, which is the readable
name of your wireless access point, has to be broadcasted by your router for this
to work. If you have it hidden, you should use the console method instead. Follow
these steps to set up a desktop:
1. Left-click on the network icon found at the end of the menu bar on the
right-hand side.
2. All unhidden networks will be displayed.
3. Left-click on the network you would like to connect to.
4. Enter your password and click on OK.
5. After a few seconds, the icon will stop flashing.
6. You can right-click on the network icon to adjust the network settings.
Setting up from a console
If you plan to run your Raspberry Pi in headless mode (where you do not have
a monitor or the keyboard connected), you do not need to access the desktop by
default, and you also cannot use the desktop network utility.
In the latest distributions of Raspbian, the SSH service is enabled by default, and
you can SSH into your Raspberry Pi. If you have just joined your Wi-Fi network, you
can tweak its settings. This is intended when you use Ethernet in order to set up the
Wi-Fi. You can now log in via the SSH, and enter the following command:
sudo nano /etc/network/interfaces
[ 18 ]
Chapter 2
This will open the included file editor, called nano, and present you with your
current interface configuration. We are interested in the last few lines. If you do not
see some of the lines, you can type them in manually:
auto lo
iface lo inet loopback
iface eth0 inet dhcp
allow-hotplug wlan0
auto wlan0
iface wlan0 inet dhcp
wpa-ssid "ssid"
wpa-psk "yourpassword"
To save the file, press CTRL + X, followed by Y, and finish by pressing Enter.
The allow-hotplug command will do as its name suggests: it allows you to plug
wireless adapters in and out assigned to the wlan0 interface. Auto wlan0 tells
Raspbian to configure the interface automatically based on the settings you provide.
We need to replace SSID and the password with the details of your router, keeping
the text enclosed within quotation marks. This is the most basic configuration that
can be used.
There is one problem with this configuration, though: if the wireless disconnects
from your router, the interface will not be brought back up automatically. There
are many scripts that try to solve this problem. The configuration requires that you
know extra details about the wireless configuration. The next section offers a fully
automatic way to do this. We will use wpa-supplicant, which is now installed by
default with Raspbian. In /etc/network/interfaces, we change the last few lines
to the following:
allow-hotplug wlan0
iface wlan0 inet manual
wpa-roam /etc/wpa_supplicant/wpa_supplicant.conf
iface default inet dhcp
We need to go to the /etc/wpa_supplicant directory, create the file, and edit
wpa_supplicant.conf:
sudo touch wpa_supplication.conf
nano wpa_supplication.conf
[ 19 ]
Preparing a Network
Downloading the example code
You can download the example code files for this book from your
account at http://www.packtpub.com. If you purchased this
book elsewhere, you can visit http://www.packtpub.com/
support and register to have the files e-mailed directly to you.
You can download the code files by following these steps:
• Log in or register to our website using your e-mail address
and password.
• Hover the mouse pointer on the SUPPORT tab at the top.
• Click on Code Downloads & Errata.
• Enter the name of the book in the Search box.
• Select the book for which you're looking to download the
code files.
• Choose from the drop-down menu where you purchased
this book from.
• Click on Code Download.
You can also download the code files by clicking on the Code Files
button on the book's webpage at the Packt Publishing website. This
page can be accessed by entering the book's name in the Search box.
Please note that you need to be logged in to your Packt account.
Once the file is downloaded, please make sure that you unzip or
extract the folder using the latest version of:
• WinRAR / 7-Zip for Windows
• Zipeg / iZip / UnRarX for Mac
• 7-Zip / PeaZip for Linux
In nano, a simple text editor, we need to type the following:
ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1
network={
ssid="ssid"
proto=WPA RSN
key_mgmt=WPA-PSK
pairwise=CCMP TKIP
group=CCMP TKIP
psk="password"
}
[ 20 ]
Chapter 2
The configuration file contains some extra details about the connection. The way the
supplicant works is that it will try to connect using the defined parameters for proto,
pairwise, and group. You might have to adjust key_mgnt, but WPA-PSK is the most
common configuration for modern wireless routers.
This method will also allow you to connect to your router if it does not broadcast
its SSID.
It is a common misconception that disabling the SSID broadcast
protects your network. There are tools that can still find SSID
names using normal wireless cards without any effort, even
though you have turned this off. The best security is to use the
latest encryption protocol and a complex password.
Using wicd-curses
Using the wicd-curses package is a simpler way of setting up wireless and even
wired interfaces in the console. The package allows you to edit advanced options
such as a static IP, DNS, and hostnames. A daemon also runs in the background,
which automatically reconnects the interface if the wireless signal drops out and is a
more reliable way of maintaining a wireless network in poor signal areas. To use this
package, you should comment out any settings in the wpa_supplicant interfaces file:
Installing this package will install many other dependency
packages and can take up in excess of 8 MB of extra space.
Some sources also claim that running this daemon uses more
overhead, but this sounds like a fair price to pay for ease of
use and reliability, especially with Raspberry Pi 2.
sudo apt-get install wicd-curses
sudo wicd-curses
You will get a console screen with a list of available wireless access points.
Use the cursor keys to select your access point, and press the right arrow key
to edit its properties.
If you see the message that no wireless networks were detected,
try to open the preferences window by pressing P, and type
wlan0 in the wireless interface field.
Once you are in the configuring preferences screen for wireless networks, you would
only need to enter your password in the key field. Save the settings by pressing F10.
[ 21 ]
Preparing a Network
If you set up the wireless connection using a wired connection, you will need to
press C, which will connect to the access point. Keep an eye on the status LED on
your Wi-Fi (if it has one). You should see it start to flicker, and after a few seconds, it
should become solid, which means a connection has been established. At this point,
it is highly likely that the SSH session will be dropped because the wired connection
gets disabled. You should unplug the wired connection and reconnect using the
wireless IP or hostname.
You can find the wireless IP by logging into your router via the
web interface and looking at the DHCP list.
A static network address
Some DHCP servers on routers tend to change your private address every now and
then. Setting a static private address is a quick way to prevent this from happening,
and it is easier to remember what the IP address is.
However, many newer routers have the ability to assign a preferred IP address in the
DHCP settings or will automatically assign a long-term IP to the device based on its
MAC address. A long-term IP usually means that the router is reset to factory defaults
or it will run out of IP addresses and replace the oldest entry in the DHCP list.
The downfall of using static addresses with most home routers is that the router
might not know about this device. The reason for this is because it would have to
scan the entire network endlessly, thus taking up valuable resources. If the DNS
service does not advertise the IP address of the Raspberry Pi, you will not be able
to use its hostname (which is, by default, raspberry), and instead, you will have to
type in the full IP address. Furthermore, if you want to use your Raspberry Pi as a
media center, it will take much longer or may even not show up in the network list.
Worst of all, some routers will not allow you to forward ports to your Raspberry Pi if
it is not in the DHCP client list.
It is good practice to always have a DHCP server control that's assigned IP addresses
on the network so that the DNS server running beside it can work properly. Assigning
a static IP address is easy with wicd-curses, but you could disable DHCP and DNS on
your router and use your Raspberry Pi as a separate firewall, DHCP, and DNS server.
Setting up your own DHCP and DNS is not covered in this book as the topic itself
could span several chapters depending on your needs.
[ 22 ]
Chapter 2
Testing and benchmarking your network
These are essential tests that can be carried out to troubleshoot network problems.
You can also use some of these advanced techniques to benchmark your network.
Basic tests
The simplest way to check whether you are connected to the Internet is to ping a
remote address.
The following tests were carried out over Wi-Fi to not only test
the reliability of the Wi-Fi connection but to also achieve the best
stability; it is always recommended that you use an Ethernet
connection. These examples demonstrate the various bottlenecks
that you may encounter when using Wi-Fi.
We can ping http://www.google.com, but we can also use shorthand and an
easy-to-remember IP address, such as 8.8.8.8, which is Google's public DNS server.
This IP address will resolve to the nearest Google DNS server in your area, and even
if it goes down, there are many backup servers, making this a reliable test:
ping -c 1 google.com
ping -c 1 8.8.8.8
[ 23 ]
Preparing a Network
A ping can help you determine whether you have access to the Internet. You may
want to check how fast you can download files to the Raspberry Pi. We will use
popular website, http://www.speedtest.com, to help us do this directly in the
command line. This can be represented in one line:
wget --output-document=/dev/null
http://speedtest.wdc01.softlayer.com/downloads/test500.zip
My Raspberry Pi is connected to a fast wireless network connection, which is
connected to a 75 megabit downstream-capable ISP. In the following screenshot, you
can see that I've achieved about 4.27 megabytes. This varies greatly from site to site.
The server used here is in America.
Advanced benchmarking tools
You may be a bit more serious about the performance of your network. Here are
a few advanced ways to push your network to the maximum.
A speedtest application
There is a speed test application available on GitHub. It offers more advanced
options than the command-line technique we used earlier as it automatically picks
the nearest server and starts downloading a large file from there. The benefit of using
the closest server will better demonstrate the maximum capacity of your wireless
network or your ISP downstream using a wired connection.
Furthermore, the application also benchmarks your upstream bandwidth. This
may be important to you if you were thinking of hosting applications for public
Internet usage.
We will need to install git using aptitude's package manager. We do this by typing
apt-get in the command line:
sudo apt-get install git-core
[ 24 ]
Chapter 2
Follow the on-screen instruction to install the git package. Using the /tmp directory
is ideal for short term applications. This directory in Raspbian is cleared out on each
reboot or power failure. If you wish to keep the speed test application for future use,
create a new directory in your home directory and update the path appropriately:
cd /tmp
git clone https://github.com/sivel/speedtest-cli.git
cd speedtest-cli
./speedtest_cli.py
iPerf
iPerf is a network administrator's secret tool that is included with Raspbian. It is
a tool that tests a network by creating TCP and UDP streams. iPerf has client and
server functionality, so it requires another computer, which known as the server.
This can be another Raspberry Pi or computer that has iPerf installed on it.
This application will push the boundaries of your network interface and architecture.
You can also use iPerf is to detect packet loss in a complex network, such as the
Internet. If you have a virtual machine on the Internet, try installing iPerf on it and
comparing the results of your local network against those found on the Internet. Let's
install iPerf on the Raspberry Pi and remote computer:
sudo apt-get install iperf
The server will be listening for a connections type, so type the following:
iperf –s
The client will show you all the statistics related to the tests that are carried out:
iperf –c <ip address of server or domain name of public server>
Recommended bandwidth
A basic bandwidth of 256 kilobits of an up-and downstream is recommended for low
use hosting of any kind. You can get away with 64 kilobits for personal use in the
form of a basic website or the transfer of text data such as JSON.
It is standard practice for home ISP providers to supply you with a much larger
downstream bandwidth, and with many countries reclassifying the Internet as a
public utility, access to it should be faster and easier than before. But there is one
main difference between home and business packages: it is the upstream bandwidth
that matters when trying to serve content to users on the Internet. Typically, home
Internet is only a fraction of the downstream, whereas businesses get a larger portion
of the upstream, sometimes even equal, by purchasing Synchronous DSL (SDSL).
[ 25 ]
Preparing a Network
If you plan on using VoIP with Asterisk, a small upstream might cause terrible
delays and jitters. But Asterisk comes licensed with GSM codecs that should work
with an upstream bandwidth of 64 kilobits for a single call. You may purchase closed
source codecs that work on much slower connections at the cost of voice quality.
Internet configurations
There are some obstacles to resolve before you can successfully host any kind of
Internet application. The solutions are influenced by the package that your ISP
provides to you, but almost every problem can be worked around.
[ 26 ]
Chapter 2
Home packages
The most fundamental part of home packages is that you almost always have a
dynamic IP address. The increasing implementation of IPv6 is meant to eliminate
this problem by assigning an IPv6 address to all your devices, accessible by anyone
that knows it, from anywhere in the world. Some ISPs will allow you to upgrade to a
static IP, but there can still be some limitations. The problem with having a dynamic
IP is that it may change without notice. So, if you try to access your network from the
Internet using an IP one day, it will certainly stop working after a while. This lease
time varies from ISP to ISP because some are as short as a few hours, and others can
last for years. If you don't know your current Internet IP address while you are in a
remote place, finding out what it is can be quite inconvenient.
One of the best known solutions is to use a dynamic DNS service. Many Internet
routers will have some kind of dynamic DNS setting available, even the one provided
by your ISP. A dynamic DNS client is a program that automatically updates the DNS
records of a public domain name. There are a handful of free dynamic DNS services.
Business packages
Business packages will almost always include a static IP address or an option to
purchase one. This really gets rid a lot of work for workarounds that need to be
applied with home packages. You can use the IP address provided to you, but even
on the rarest occasion, it may be changed to another IP; however, you will be warned
about this in advance.
The other benefits are that ISPs will allow you to change the reverse DNS lookup
of your IP, a service that is unavailable with home packages. This service is very
important if you plan on running a small mail server. This is one of the prerequisites
that needs to be configured so that other mail domains know who you are. The only
way to solve this problem at home is to use a paid for mail exchange to send and
receive e-mails using custom domain names.
Many business packages offer unlimited and unshaped traffic. ISPs might deliberately
throttle certain ports on home broadband connections to make them slower and less
reliable. Some ISPs go to extreme measures and block these ports on home packages;
for example, ports 25, 80, 110, and 443 are used for mail and web servers.
If you plan on using the Raspberry Pi for some home experiments, private use, or
educational purposes, then all you need to do is spend a little extra time configuring
everything correctly. Be aware, though, that hosting production services on a
home broadband may be against the terms and conditions of your contract. If you
anticipate high usage, it is a much better option to purchase a business package.
[ 27 ]
www.allitebooks.com
Preparing a Network
Dynamic DNS
Dynamic DNS is a way of updating name records for a public DNS. Paid solutions
usually offer real-time updates and free services have a minimum time before the
change is published.
I have been using the paid service by NO-IP, which is fairly priced for the features
it provides. It also offers free domains and services. It also provides clients for many
operating systems, including a Raspbian Linux-compatible client. You may use any
service you like as the protocol is the same for everybody.
Installing a client
I have a premium account registered with NO-IP. I allocated a subdomain called
pi.kula.solutions. It automatically detected my public IP and set the record of the
domain accordingly.
Visit http://www.mxtoolbox.com to verify live changes to
domain name records. It also has several other useful tools.
Once you have created a dynamic DNS account, you can install the client on the
Raspberry Pi. During the installation, you will be asked for your credentials and
which domains to update.
The make –j4 command speeds up compile time on Raspberry
Raspberry Pi 2. If you are not using one, do not use –j4.
The commands to install a client are as follows:
mkdir /home/pi/noip
cd /home/pi/noip
wget http://www.no-ip.com/client/linux/noip-duc-linx.tar.gz
tar vzxf noip-duc-linx-tar.gz
cd noip-{version}
sudo make –j4
sudo make –j4 install
After running the make installation, you will be prompted to log in with your No-IP
account username and password. The interval must be 5 minutes or more. You can
now start the service:
sudo /usr/local/bin/noip2
[ 28 ]
Chapter 2
You now have a domain name that points to your home IP address. As we progress
through this book, you might want to test various applications, and to do this, you
will need to open ports on your router.
Unfortunately, configuring your router is not part of this book as each vendor
handles this differently. Consult the manual that came with your router to learn how
to open and forward ports. Opening unnecessary ports can put you at a higher risk
of being hacked.
The free Dynamic DNS domain workaround
You might not like the domain names provided by the Dynamic DNS providers, or
you may not be able to afford a premium service. Instead, you may want to use a
domain that you already own but is hosted somewhere else. I own another domain
that is not registered with NO-IP called http://www.piotrkula.com. I will use this
as an example to access my Raspberry Pi using http://pi.piotrkula.com/ with a
free NO-IP domain such as http://randomname.no-ip.me.
Log in to your domain name DNS panel, and add a new subdomain. Edit the DNS
records and make sure that they have absolutely no A records associated with
them. You will need to add a new CNAME record and the value; in my case, it is
randomname.no-ip.me.
Now the http://pi.piotrkula.com/ domain tells visitors to take a look at the
randomname.no-ip.me DNS record instead. The visitor will find an A record at NOIP, and this will tell them the correct IP address, which is your home IP with port 80
forwarded to the Raspberry Pi. This is NOT a redirect and the top domain name will
NOT change. Visitors will not even know you are using a dynamic DNS unless they
inspect your private domain record and track down that CNAME belongs to a dynamic
DNS company. But as long as the domain works, there is no reason to inspect it.
The only drawback of using this workaround is speed. Whenever a visitor looks up
the DNS records for the first time, it might take several seconds before a connection
is established. After the first request, things go smoothly as the client usually caches
the IP for the duration of the session, regardless of what TTL is set on your A record.
Every new session might experience this delay as TTL forces the client to read the
DNS again. Some dynamic DNS providers might even deliberately slow down DNS
lookups in the hope that you will upgrade to premium DNS servers for a premium
service. As far as I know, NO-IP has never done this and performed really fast, even
when I used it for free domains.
[ 29 ]
Preparing a Network
Summary
It is important to understand how your networks are configured; this includes both
the Internet side and your local network. This in-depth understanding will surely
help you troubleshoot particular problems on your own.
We now have our Raspberry Pi connected to our private network and configured
a domain name that can be accessed by anybody on the Internet.
In the next few chapters, you will learn more about various services that can be made
available to friends over the Internet.
[ 30 ]
Configuring Extra Features
There are some extra features on the Broadcom chip that can be used out of the
box or activated using extra licenses that can be purchased. Many of these features
are undocumented, and are found by developers or hobbyists working on various
projects for Raspberry Pi.
In this chapter, you will learn how to keep Raspberry Pi up to date and also how to
use the extra features of the GPU.
Updating Raspberry Pi
The Raspberry Pi essentially has three software layers: the closed source GPU boot
process, the boot loader (also known as the firmware), and the operating system.
At the time of writing book, we cannot update the GPU code. But maybe, one day,
Broadcom or hardware hackers will tell us how do to this.
This leaves us with the firmware and the operating system packages. Broadcom
releases regular updates for the firmware as precompiled binaries to the Raspberry
Pi Foundation, which then releases them to the public. The Foundation and other
community members work on Raspbian, and release updates via the aptitude
repository; this is where we get all our wonderful applications from.
It is essential to keep both the firmware and the packages up to date so that you can
benefit from bug fixes and new or improved functionality from the Broadcom chip.
Raspberry Pi 2 uses ARMv7 as opposed to Pi 1, which uses ARMv6. It is
recommended to use the latest version of the Raspbian release to benefit from the
speed increase. Thanks to the upgrade to ARMv7, it now also supports the standard
Debian Hard Float packages and other ARMv7 operating systems, such as Windows
IoT Core.
[ 31 ]
Configuring Extra Features
Updating the firmware
Updating the firmware used to be quite an involved process, but thanks to a user on
GitHub, who goes under by the alias Hexxeh, we have some code to automatically do
this for us. You don't need to run this as often as apt-update, but if you constantly
upgrade the operating system, you may need to run this if advised or if you are
experiencing problems with new features or instability.
The rpi-update command is now included as standard in the Raspbian image, and
we can simply run the following command:
sudo rpi-update
After the process is complete, you will need to restart your Raspberry Pi in order to
load the new firmware.
Updating packages
Keeping Raspbian packages up to date is also very important, as many changes
might work together with the fixes published in the firmware. Firstly, we will update
the source list, which downloads a list of packages and their versions to the aptitude
cache. Then, we will run the upgrade command, which will compare the packages
that are already installed and also compare their dependencies, and then download
and update them accordingly:
sudo apt-get update
sudo apt-get upgrade
Updating some packages might break your existing
custom code or applications if there are major changes in
the libraries. If you are running custom code, you should
always check the release notes if you need to change
anything in your code before updating.
Updating distribution
We may find that running the firmware update process and package updates does
not always solve a particular problem.
If you are using a release such as debian-armhf, you can use the following
commands without the need to set everything up again:
sudo apt-get dist-upgrade
sudo apt-get install raspberrypi-ui-mods
[ 32 ]
Chapter 3
Outcomes
If you have a long-term or production project that will be running independently, it
is not a good idea to log in from time to time to update the packages. With Linux, it
is acceptable to configure your system and let it run for long periods of time without
any software maintenance. You should be aware of critical updates though, and
you should evaluate if you need to install them. For example, consider the major
Heartbleed vulnerability in SSH. If you had a Raspberry Pi directly connected to the
public Internet, this would require instant action.
Windows users are conditioned to be updated frequently, and it is very rare that
something will go wrong. But on Linux, running updates will update your software
and operating system components, which could cause incompatibilities with other
custom software. For example, you used an open source CMS web application
to host some of your articles. It was specifically designed for PHP version x, but
upgrading to version y also requires the entire CMS system to be upgraded.
Sometimes, less popular open source sources may take several months before the
code gets refactored to work with the latest PHP version, and consequently, they
may unknowingly upgrade to the latest PHP or may partially break your CMS.
One way to try and work around this is to clone your SD card and perform the
updates on one card. If you encounter any issues, you can easily go back and use the
other SD card.
A distribution called CentOS tries to deal with this problem by releasing updates
once a year. This is intended to make sure that everybody has enough time to test
their software before you can do a full update with minimal or even no breaking
changes. Unfortunately, CentOS has no ARM support, but you could follow this
guideline by updating packages when you need them.
Hardware watchdog
A hardware watchdog is a digital clock that needs to be regularly restarted before it
reaches a certain time.
Just like in the TV series Lost, there is a dead man's switch hidden on the island that
needs to be pressed at regular intervals; otherwise, an unknown event will begin. In
terms of the Broadcom GPU, if the switch is not pressed, it means that the system has
stopped responding, and the reaction event is to restart Raspberry Pi and reload the
operating system with the expectation that it will resolve the issue, at least temporarily.
[ 33 ]
Configuring Extra Features
Raspbian has a kernel module included—which is disabled by default—that deals
with the watchdog hardware. A configurable daemon that runs on the software
layer sends regular events (like pressing a button), referred to as a heartbeat to the
watchdog, via the kernel module.
Enabling the watchdog and daemon
To get everything up and running, we need to do a few things, as follows:
1. Add the following in the console:
sudo modprobe bcm2708_wdog
sudo vi /etc/modules
2. Type the line of text bcm2708_wdog to the file. Then, save and exit by
pressing Esc and typing :wq command.
3. Next, we need to install the daemon that will send the heartbeat signals every
10 seconds. We use chkconfig, add it to the startup process, and then enable
it, as follows:
sudo apt-get install watchdog chkconfig
sudo chkconfig --add watchdog
chkconfig watchdog on
4. We can now configure the daemon to do simple checks. Edit the following
file:
sudo vi /etc/watchdog.conf
5. Uncomment the lines max-load-1 = 24 and watchdog-device by removing
the hash (#) character. The max load means that it will take 24 Pi's to
complete the task in 1 minute. In normal usage, this should never happen
and would only really occur when the Raspberry Pi has hung.
6. You can now start the watchdog with which configuration. Each time you
change something, you will need to restart the watchdog:
sudo /etc/init.d/watchdog start
There are some other examples in the configuration file that may be of interest.
[ 34 ]
Chapter 3
Testing the watchdog
In Linux, you can easily place a function into a separate thread that runs in a new
process using the & character on the command line. Exploiting this feature together
with some anonymous functions, we can issue a very crude but effective system halt.
This is a quick way to test whether the watchdog daemon is working correctly, and
it should not be used to halt the Raspberry Pi. It is known as a fork bomb, and many
operating systems are susceptible to this.
The random-looking series of characters are actually anonymous functions that
create other new anonymous function. This is an endless and uncontrollable loop. It
most likely adopted the name bomb, because once it starts, it cannot be stopped. Even
if you try to kill the original thread, it creates several new threads that need to be
killed. It is just impossible to stop, and eventually, it bombs the system into a critical
state, also known as a stack overflow. Type these characters into the command line
and press Enter:
: (){ :|:& };:
After you press Enter, the Raspberry Pi should restart after about 30 seconds, but it
might take up to a minute.
Enabling extra decoders
The Broadcom chip actually has extra hardware for encoding and decoding a few
other well-known formats. The Raspberry Pi Foundation did not include these
licenses because they wanted to keep the costs down to a minimum, but they have
included the H.264 license. This allows you to watch HD media on your TV, use the
webcam module, or transcode media files.
They did provide a way for users to buy separate licenses if you want to use these
extra encoders or decoders.
At the time of writing, the only project to use these hardware codecs was the
OMXPlayer project maintained by XBMC. The latest Raspbian package has the omx
package included.
Buying licenses
You can go to http://www.raspberrypi.com/license-keys/ to buy licenses,
which can be used once per device. Follow the instructions on the website to get
your license key.
[ 35 ]
Configuring Extra Features
MPEG-2
Known as H.222/H.262, it is the standard of video and audio encoding widely used
by digital television, cable, and satellite TV. It is also the format used to store video
and audio data on DVDs.
This means that watching DVDs from a USB DVD-ROM drive should be possible
without any CPU overhead whatsoever. Unfortunately, there are no packages that
use this hardware directly. But hopefully, in the near future, it will be as simple
as buying this license, which will allow us to watch DVDs or stream videos in this
format with ease.
VC-1
VC-1 was formally known as SMPTE 421M and was developed by Microsoft. Today,
it is the official video format used in the Xbox and Silverlight framework. The format
is supported by HD-DVD and Blu-ray players.
The only use for this codec would be to watch Silverlight-packaged media; its
popularity has grown over the years, but it still not very popular. This codec may need
to be purchased if you would like to stream videos using the Windows 10 IoT API.
Hardware monitoring
The Raspberry Pi Foundation provides a tool called vcgencmd, which gives you
detailed data about various hardware used in the Raspberry Pi. This tool is updated
from time to time and can be used to log the temperature of the GPU, voltage levels,
processor frequencies, and so on. Some commands for monitoring are as follows:
• To see a list of supported commands, we type the following in the console:
vcgencmd commands
• As newer versions are released, there will be more commands available here.
To check the current GPU temperature, we will use the following command:
vcgencmd measure_temp
• We can use the following command to check how RAM is split between the
CPU and GPU:
vcgencmd get_mem arm/gpu
• To check the firmware version, we can use the following command:
vcgencmd version
[ 36 ]
Chapter 3
The output of all these commands is a simple text that can be parsed and displayed
on a website or stored in a database.
Summary
Raspberry Pi has a very capable GPU and ARM System on Chip (SOC) with features
that might not have been disclosed or discovered yet. Open development is slowed
down by the fact that Broadcom is keeping many aspects closed source; and even if
somebody gets a peek at some source code, they enforce strict nondisclosure terms
and conditions. Raspbian has had a few years to mature and many improvements
have been developed since the initial release of the hardware. There is still a strong
hype around Raspberry Pi, which has brought you, me, and thousands of people to
this hack space.
This chapter's intention was to teach you about how hardware relies on good
software, but most importantly to show you how to use leverage hardware using
ready-made software packages.
In the next chapter, we will look at how to configure a web server and a database.
For reference, you can visit the following link:
http://www.elinux.org/RPI_vcgencmd_usage
[ 37 ]
Using Fast Web Servers
and Databases
Raspberry Pi 2 is even better at working as a webserver now, thanks to its quad core
architecture. Everything described in this chapter is still compatible with Raspberry
Pi 1, but any performance tests run here are strictly for Raspberry Pi 2. The following
topics will be covered in the chapter:
• Apache versus nginx versus Kestrel
• Extra frameworks for nginx
• Installing a database
Apache versus nginx versus Kestrel
With the release of .NET 5, Microsoft has managed to bring a full stack of C#
deployment targets to Linux. ASP web applications, such as the popular ASP.MVC,
can be hosted on Linux by using Kestrel, a development web server based on libuv.
Libuv was primarily developed for use by Node.js and focuses on asynchronous
input/output.
Nginx is still the first choice in embedded devices for managing HTTP traffic as
an extremely fast and lightweight reverse proxy server, ahead of Apache.
Apache remains one of the more popular HTTP servers due to the fact that it comes
bundled with images, but is also extremely easy to install and configure. However,
it is typically used on full desktop machines or servers because it requires a lot
of resources. It is not recommended to use Apache on a Raspberry Pi or other
embedded device, and it will not be covered in this book.
[ 39 ]
Using Fast Web Servers and Databases
From the Netcraft report, we can see that the three top servers are Apache, Microsoft,
and nginx. Microsoft has been struggling to overtake Apache, but in August 2014,
for the very first time in the last 10 years, they managed to secure the first place for a
month. This was most likely caused by the fact that ASP.NET 5 was released in beta
version 1 and millions of developers rushed in to test ASP.NET on Linux, Macintosh,
and Windows.
To achieve full flexibility, we will configure nginx as the frontend HTTP Proxy,
which will allow us to run various combinations of programming languages in
tandem. Nginx will allow us to host production-ready servers. There are almost no
limits with nginx for hosting websites, and in this chapter, I will demonstrate some
of the most popular ones. Nginx on its own is excellent for serving up static files,
such as HTML, JavaScript, or Images.
Installing nginx
The easiest way to install nginx is to use apt-get. Unfortunately, the wheezy
repository only has the version 1.2 package:
sudo apt-get update
sudo apt-get install nginx
To upgrade to a later version of nginx, follow the instructions
for selective upgrades in Chapter 6, Setting Up Game Servers. Then,
reinstall nginx with the –t jessie switch.
[ 40 ]
Chapter 4
By default, nginx serves pages from /usr/share/nginx/www, but most Linux admins
tend to be more familiar with the location /var/www . It does not matter where you
keep the files as long as you choose a convention and stick with it. We will use /var/
www in this chapter:
sudo mkdir /var/wwww
Inside this directory, we will create more directories that will hold various virtual
hosts. Virtual hosts are domain names (known as server blocks in nginx), which tell
the webserver about the configuration for that requested domain or subdomain. We
will initially create a directory called html and a directory named web that will hold
static files, but will add new location blocks later, known as virtual directories:
sudo mkdir /var/www/html
sudo mkdir /var/www/html/web
Configuring the nginx virtual hosts
A virtual host in nginx is a set of rules called server blocks, which specify how to
serve HTTP traffic for a specified domain. In our configuration, we will serve content
to any domain on port 80. You may have many virtual hosts to serve different
domains or subdomains using separate server blocks with specific domain names.
This requires some more configuration and is not covered in this book.
Nginx uses the directory /etc/nginx/sites-available/ to store configuration files
for virtual hosts. On starting up, it will check another directory, /etc/nginx/sitesenabled/, and usually these files are symbolic links to the configuration files in sitesavailable. If a file exists there, it will load the configuration file.
There should be a file called default, which is the default website that nginx serves.
We will remove the symbolic link of the default website, create a new configuration
file and symbolic link, and finally, restart nginx:
We will use the symbolic name nginxhtml, but feel free to use
any name you like for the virtual host.
sudo service nginx stop
sudo unlink /etc/nginx/sites-enabled/default
sudo touch /etc/nginx/sites-available/nginxhtml
[ 41 ]
Using Fast Web Servers and Databases
Edit the configuration file found at /etc/nginx/sites-available/nginxhtml and
add the following to it:
server {
listen 80 default_server;
location / {
root /var/www/html/web;
index index.html;
}
}
This is the most basic configuration to serve up standard static files for any browser.
This will be enough for us to use jQuery to run a client-side script, which will use
AJAX requests to our APIs created later in this chapter. Let's enable the website:
cd /etc/nginx/sites-enabled
sudo ln -s /etc/nginx/sites-available/nginxhtml
sudo service nginx start
To start serving up basic pages, follow these steps:
1. Create a filename called index.html in the /var/www directory.
2. Place some basic HTML markup into it (check the code folder for a complete
sample file with the jQuery download instructions and examples of calling
the various APIs we will create).
3. Use a browser on another computer on your network that can access your
Raspberry Pi and type the address http://rapsberrypi or http://your.
pi.ip.address.
4. You should see your basic webpage now.
We should reload nginx after each configuration change by typing in the following
command line:
service nginx reload.
If you get start failed, you can run the next command to test the configuration
file, which will display any errors with details:
sudo nginx -c /etc/nginx/nginx.conf -t
[ 42 ]
Chapter 4
Extra frameworks for nginx
Now that we have nginx up and running, we have a wide choice of frameworks or
programming languages that we can use to create programs that will expose APIs to
our basic HTML page.
We will leverage the nginx location blocks (virtual directories) to allow us to mix
and match programming languages to deliver rich content to simple HTML pages
using jQuery Java Scripting.
Python API
Python comes pre-installed with Raspbian and is the programming language
of choice for Raspberry Pi. It has a rich library that allows you to access the GPIO
and other system software, and there is an abundance of documentation available
on the Internet.
It is an easy first language to learn, as you can create applications with fewer lines
of code than in C++ or Java. You need to understand that Python is a programming
language and not a web content delivery framework. This said, it is still possible to
deliver web content with Python by writing specific responses. This will allow us to
leverage the Python programming language to create simple APIs that can deliver
data to any other software calling the API's URL.
Executing Python
You can execute any Python script in the terminal, but nginx cannot directly execute
Python scripts. To fix this, we need to install uWSGI. We will configure a new location
block that will ask uWSGI to execute Python on behalf of nginx, and the resulting
text will be sent back to the client. We will use the latest build of uWSGI downloaded
directly from their website. This will build and place the necessary files into the
/home/pi directory. It should take about 80 seconds to compile on a Raspberry Pi 2:
cd /home/pi
sudo curl http://uwsgi.it/install | bash -s cgi /home/pi/uwsgi
This places the uWSGI binary in /home/pi, and we need to create a configuration file
for uWSGI in that directory. Create a file named uwsgi_config.ini and enter the
following text:
[uwsgi]
plugins = cgi
socket = 127.0.0.1:9000
chdir = /usr/lib/cgi-bin/
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module = pyindex
cgi=/cgi-bin=/usr/lib/cgi-bin/
cgi-helper =.py=python
The actual Python script files will be located in /usr/lib/cgi-bin instead of
/var/www/, as nginx doesn't actually execute Python files; it redirects execution to
uWSGI. We also need to map the nginx location block /cgi-bin to /usr/lib/cgibin inside the uWSGI configuration file. We can now start the uWSGI process with the
configuration. This will block your terminal; it has to run the whole time for nginx to
be able to communicate with the daemon. Open a new terminal or run it in screen:
cd /home/pi
sudo ./uwsgi ./uwsgi_config.ini
Next, we will add a new location block for our default server that is purely for
Python's execution. This new location block is also known as a virtual directory,
where every request on the location http://raspberrypi/cgi-bin will actually ask
uWSGI to execute Python files in the /usr/lib/cgi-bin directory.
Add the following location block under the previous location block in the existing
nginxhtml file:
location / {
include uwsgi_params;
uwsgi_modifier1 9;
uwsgi_pass 127.0.0.1:9000;
}
In /usr/lib/cgi-bin, we will create a file called temp.py that will simply return
an HTTP header for the browser and the CPU temperature as text. Indentation is
important here as it defines the function block:
#!/usr/bin/env python
import os
# Return CPU temperature as a character string
def getCPUtemperature():
res = os.popen('vcgencmd measure_temp').readline()
return(res.replace("temp=","").replace("'C\n",""))
#We have to print a valid HTTP header first so the browser
#will know how to decode the data
print "Content-type: text/html\n\n"
temp1=float(getCPUtemperature())
print temp1
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Chapter 4
One last thing we need to do is make the Python script executable:
chmod +x temp.py
If you reload the webpage that uses the sample code provided, you should now
you can see the Raspberry Pi's temperature refreshed every second in the Python
paragraph. You can also test it by navigating your browser to http://rasbperrypi/
cgi-bin/temp.py.
This is an extremely basic sample of how you could provide data from Python in a
Web API way. This is not a standard Web API JSON/XML implementation, but it is
extremely lightweight and fast and an easy way to provide data via HTTP requests.
Node.js
Node.js is a platform built on the Google V8 JavaScript engine that uses event-driven
and non-blocking I/O.
It is known as the JavaScript web programming language. On the surface, this is true,
but deep inside Node.js binary, it uses C/C++ to access the local system resources,
and then standard modules written in JavaScript (file system, networking buffering,
cryptography, data streams, and so on) expose APIs from which you can then extend
your own application with. You will never actually need to write any C/C++, and
all the packages are provided as JavaScript; this is why Node.js is so easy to use and
dubbed the JavaScript programming language.
It is a great runtime environment for Raspberry Pi because it is extremely lightweight
on resources but optimized to handle hundreds of requests across many node
applications.
Installing Node.js
We will use an auto setup script for Node.js. Execute the following command:
curl -sL https://deb.nodesource.com/setup | sudo bash -
We can now install Node.js from the new repository.
sudo apt-get install nodejs
Node.js and NPM are now installed. To check whether Node.js is installed correctly,
you can execute the following command:
node –-version
npm –version
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What is NPM
NPM stands for Node Package Manager. You can find many ready to use
applications and libraries at http://www.npmjs.com. These are ready to be installed
with a single command line, which is provided at the packages' landing page.
Try and search for Raspberry on the website to find some
interesting packages made specifically for Raspberry Pi.
The Node.js server
Typically, you would execute Node.js files using nodejs helloword.js and that
would run the program without any web capabilities. In order for us to use Node JS
in a Web API way, we need to create a Node HTTP server, which can then react to
your Web Requests proxied via Nginx.
As with all the examples, we want nginx to be able to provide a standard and easy way
to proxy web requests via port 80 into Raspberry Pi's internally running applications.
This makes it easy to remember URLs and simpler to build frontend pages and offer
some security if you are going to open your Raspberry Pi to the World Wide Web.
We will add a new location block to the existing file in the /etc/sites-available/
nginxhtml directory:
You can run multiple node applications like this by creating
new location block names (virtual directories) and adjusting
the proxy pass setting that your node application is bound to.
location /node {
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header Host $http_host;
proxy_set_header X-NginX-Proxy true;
proxy_pass http://127.0.0.1:5000;
proxy_redirect off;
}
We will install two packages to help get Raspberry Pi's voltage settings. Firstly, we
will install a package called express, which will allow us to easily create RESTful
APIs, and then a pi-volts module.
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Chapter 4
The typical approach with packages is to install them in your application directory,
which is saved in /node_modules and is only accessible by that application. We
will use the –g switch, which will install the package once into the /usr/lib/node_
modules/ directory, which will be available globally to any node application you
create. This saves some space on your SD card, but it means that all your applications
using that global package must use that one specific version of the package. You can,
however, install packages, such as express globally, and then install a small package
for just one application, such as pi-volts.
Whenever you create a new application directory, you must use npm to initialize the
application. This creates a configuration file and lets Node.js know that you want
to install your application-specific packages (non-global) into this directory. A few
onscreen questions will be displayed; you can just press Enter on all the questions if
you like. Because nginx does not execute or serve up the raw Node.js files, we will
keep our naming convention similar to Python. I will demonstrate this approach in
the next few command lines:
sudo npm install express -g
cd /usr/lib
sudo mkdir node_bin
cd node_bin
sudo mkdir volts
cd volts
npm init
sudo npm install pi-volts
touch index.js
You have now set up the basic framework for your application and installed the
pi-volts package just for this Node.js application. Edit index.js and insert the
following text:
var
var
var
var
http = require('http');
express = require('express');
app = express();
volt = require("pi-volts");
// Express route for incoming requests (GET)
app.get('/node/core/voltage/', function(req, res) {
res.send(String(volts));
});
// configure Express to listen on port 5000
app.listen(5000);
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Using Fast Web Servers and Databases
We can now run this basic node server, which provides a simple API text response
with the current core CPU voltage. You can do a AJAX GET request at http://
raspberrypi/node/core/voltage, and since this is a GET, you can simply test it by
entering this address into your browser after starting the server:
npm index.js
Now, you can update your index.html file at /var/www/html/web and use jQuery
to do a simple GET and update an element on your page. The result varies between
1.2 and 1.3125 (the full sample is provided in the code library):
$.get('/node/core/voltage', function(data) {
$('#cpuvoltage').text(data);
});
.NET and ASP.MVC
To work with Microsoft's .NET framework, we first need to install the latest version
of Mono. The typical way is to compile Mono from the GIt source, but it takes
roughly 6 hours to complete on Raspberry Pi 2. I have tried to come up with a crosscompiling tutorial, but I have not managed to get anything simple or robust enough
to demonstrate in this book.
Unfortunately, at the time, the Wheezy and Jessie repositories only have versions
that do not support .NET 5 fully. A faster and better way is to use the newer versions
maintained by the official Xamarin repository.
These commands will add the official Xamarin repository, update any required
packages, and finally, install Mono, which requires about 300 MB of space and takes
about 10 minutes to complete. Type in the following commands:
sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys
3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF
echo "deb http://download.mono-project.com/repo/debian wheezy main" |
sudo tee /etc/apt/sources.list.d/mono-xamarin.list
sudo apt-get update && sudo apt-get upgrade
sudo apt-get install mono-complete
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Chapter 4
Prerequisites for .NET 5
Please be aware that the terminology and commands may change
as the .NET vNext project leads up to version 1. If any commands
do not work, please refer to https://github.com/aspnet/
home for more information.
At this point, we can check that Mono has been properly installed by typing in the
following command:
mono --version
For Kestrel to work properly, we need to compile Libuv and link the new libraries
manually:
sudo apt-get install automake libtool curl unzip
wget https://github.com/libuv/libuv/archive/v1.4.2.tar.gz
sudo tar zxfv v1.4.2.tar.gz -C /usr/local/src
cd /usr/local/src/libuv-1.4.2
sudo sh autogen.sh
sudo ./configure
sudo make
sudo make install
sudo ldconfig
.NET 5 for Linux comes with some new terminology, which I will try my best to
explain:
DNX is short for Dot Net Execution Environment and is used to bootstrap and
execute .NET applications. To install DNX, we first need to install DNVM, which
stands for Dot Net Version Manager.
DNVM allows you to install various versions of DNX side by side as a way to allow
applications to run on various versions of .NET 5.
DNU, which stands for Dot Net Package Updater, essentially provides a way to
restore NuGet packages on Pi on which the project depends, similar to Node.js NPM.
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Installing DNVM, DNU and DNX
DNVM, DNU, and DNX can be installed using a one-line command on the terminal
thanks to a script that will execute all the other required operations. Please note that
the stable uses old command lines: K, KRE, KPM, and KVM. To stay up to date with
patches, we will use the dev (bleeding edge) branch. These patches remove a lot
of extra commands that will not be covered here. As soon as version 1 is released,
please use the stable branch:
cd /home/pi
curl -sSL https://raw.githubusercontent.com/aspnet/Home/dev/dnvminstall.
sh | DNX_BRANCH=dev sh && source /home/pi/.dnx/dnvm/dnvm.sh
Installing DNX
To install the latest version of DNX (.NET 5), which as of writing is Beta4, on the dev,
we can now just type in the following one-line command:
dnvm upgrade
dnx
Congratulations, you now have .NET 5 installed on your Raspberry Pi!
Running the MVC website
During the previous process, only the .NET 5 runtime environment was installed,
which allowed for cross-platform execution of the .NET applications.
To get a quick MVC website running, we will use the examples from the ASPNET
Github repository. During beta, please make sure you select the correct directory
of the DNX version that was installed. In the rest of this chapter, we be using the
v1.0.0-beta4 directories and DNX. When the final is released, it will be known as
v1.0.0.
Please double-check the DNX version and the sample version
you are using. A mismatched DNX and sample will result in
some of the samples failing to run.
We will clone the main APSNET Home Sample and change into the specific beta
directory. We will run a package restore in this directory to install all the required
dependencies, such as Kestrel:
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Chapter 4
DNU restore might take some time to download the required
packages for the first time. The dnx . kestrel command might
also take some time for the first time; it will bootstraps and prebuild
the MVC website before Kestrel launches and binds to a port.
cd /var/www
sudo mkdir dotnet
cd dotnet
sudo git clone –b dev https://github.com/aspnet/Home.git
The Git clone was executed as the root user, creating all the files in the /Home
directory as the root. This will cause a problem while restoring packages and other
strange things may happen. We need to change the user recursively to pi on this
directory to fix permission problems:
sudo chown –R pi /var/www/dotnet/Home
We will now restore the required packages from the official stable repository.
You always need to run this on any new (or sample) project, but it will be a lot
faster, since the packages are now cached (replace the beta with the DNX version
you are running):
cd /Home/samples/v1.0.0-beta4/ HelloMVC
dnu restore
dnx . kestrel
The last command uses dnx to launch the MVC website using the configuration
specified in the configuration file named project.json. The port to which Kestrel
binds is also defined in the project.json file and is 5004 by default.
After running dnx . kestrel, your terminal screen will be blocked and will show
some messages generated by .NET. Once the server has started, a message will be
displayed telling you that it has started and which port it is bound to. A blinking
underscore will be visible, until you press Enter to terminate the server.
Before you press Enter, use a web browser on another computer on your network
and navigate to htttp://raspberrypi:5004. You should now see a basic MVC
example website.
Go ahead and try to compile the other samples or create your own project using the
Visual Studio Community edition.
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MVC and nginx
You may use MVC as it is with Kestrel without installing nginx, but it is strongly
recommended to use nginx as the frontend proxy, which will allow you to manage
various web applications in a mixed environment. Nginx also provides you with
more functionality, such as binding SSL certificates, which Kestrel on its own doesn't
support yet.
We can now add another location block for the dotnet proxy:
location /dotnet {
proxy_pass http://127.0.0.1:5004;
}
You can now navigate your browser to http://raspberrypi/dotnet and you
should see the same page as on port 5004.
The benefit of doing this is that you have now configured nginx to do more advanced
things with this virtual host.
For security reasons, you should only allow ports forwarded to the ports defined
in your nginx virtual hosts and block the rest, for example, Kestrel's 5004. This is
to ensure that any vulnerabilities within Kestrel cannot be exploited, while it's still
developed as a development server. The only downside is that services such as
Netcraft will identify this website as nginx and not Microsoft's Kestrel. But from a
security point of view, this is good, since a potential attacker will not know what is
actually going on behind the powerful nginx proxy.
Other .NET applications
Mono supports the full .NET 5 stack, which means that you can now easily create
console applications in Visual Studio and execute them on Raspberry Pi. Simple copy
your .exe file and run it using MONO file.exe.
You can also create traditional Windows Forms and execute them within LXDE
using the same method of MONO formsapp.exe. Native styled forms should appear
within LXDE.
With Windows IoT installed as your operating system, you will
be able to create Universal Apps leveraging the Windows 10
API, creating full hardware rendered forms, and gain access
to OpenGL via DirectX graphics and a rich API for developing
Internet of Things applications for Raspberry Pi 2. The basics will
be covered in Chapter 10, Windows IoT Core.
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Chapter 4
Installing PHP
As mentioned before, nginx is a proxy that handles web requests extremely quickly,
and to get PHP to work with nginx, we need to install an interface called FastCGI.
This will allow nginx to send requests to PHP and receive and display the response.
To help improve PHP performance, we will also install a PHP extension called APC,
which stands for Alternative PHP Cache. It is much faster and uses fewer resources
than the standard PHP caching.
After installing, PHP should be running, but we will restart it to make sure all the
extensions were loaded correctly:
sudo apt-get install php5-fpm php-apc
sudo service php5-fpm restart
Create a new directory under /var/www/ called PHP with a subdirectory web.
In the web directory, we will create a new file called index.php and add the
following content:
<?php
phpinfo();
?>
This time we will run it on a different port, as PHP has different requirements. We
will bind the new host to port 888. We will create a new server block; you can place
it in the existing configuration file or create a new sites-available/php file if you
wish:
Please avoid using port 8080, as it will be used for real-time streaming
later.
Note the fastcgi_pass setting that will be used for any other PHP
website.
server {
listen 888;
root /var/www/php/web;
index index.php;
location ~ \.php$ {
fastcgi_pass unix:/var/run/php5-fpm.sock;
fastcgi_index index.php;
include fastcgi_params;
}
}
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Restart nginx, and then with a browser on another computer, browse to http://
raspberrypi:888. You should be presented with a page that looks as follows:
Installing a database
When we think of a database on a Linux machine, the first thing that often comes to
our mind is MySQL. It is the first choice because it is free, open source, reliable, and
comes with a rich toolset. On Raspberry Pi 2 with quad cores, MySQL has become
an even more attractive solution, but I will still cover the alternative to SQLite that is
lightweight and robust.
Installing MySQL
MySQL has been around for a very long time, and unless you are looking for a
specific version, you can use the current repository to install MySQL version 5.5:
sudo apt-get update
sudo apt-get install mysql-server
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Chapter 4
You will be presented with blue-background screens asking you for the root user
password. You should write these down and keep them in a secure location, but it is
more convenient and secure to store passwords in an application such as KeePass.
It is good practice to never use the root user with MySQL for web
applications, especially the production ones available on the Internet.
Installing phpMyAdmin
A very popular SQL management tool called phpMyAdmin can be installed and used
to further manage your databases and even transact against them.
The phpMyAdmin is the only application that needs to run with root settings so that
it can fully manage MySQL. The best practice for phpMyAdmin is to only allow local
network connections for administration or via SSH. This is because it will be used
to create or delete databases, users, and passwords, and apply permission access to
these databases. You can create less privileged users to log in via the Internet if you
need too:
sudo apt-get install phpMyAdmin
During installation, you will get another blue screen asking for the web server that
should be automatically configured. Regrettably, nginx is not on the list; do not
check any box and click on OK. After a short while, a final screen will ask about
dbconfig-common; click on NO.
We need to manually configure phpMyAdmin just like any other website for
nginx. PhpMyAdmin places its files in the shared location /usr/share/phpmyadmin,
and anyone with access to the system can use this shared website to access only
their database.
In sites-available, create a new file called phpmyadmin; now use the following
configuration. Remember to create a symbolic link in sites-enabled and then
reload nginx:
server {
location /phpmyadmin {
root /usr/share/;
index index.php;
location ~ ^/phpmyadmin/(.+\.php)$ {
try_files $uri =404;
root /usr/share/;
fastcgi_pass unix:/var/run/php5-fpm.sock;
fastcgi_index index.php;
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fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
include /etc/nginx/fastcgi_params;
}
location ~* ^/phpmyadmin/(.+\.(jpg|jpeg|gif|css|png|js|ico|html|xml|
txt))$
{
root /usr/share/;
}
}
location /phpMyAdmin {
rewrite ^/* /phpmyadmin last;
}
}
This virtual host is configured to run on port 80, but in a virtual directory. The
application in this virtual directory runs on its own thread, separate from anything
else running on port 80. You can configure the previous virtual hosts to run in the
same way if you prefer this over different port numbers.
You can now browse to http://raspberrypi/phpmyadmin/setup and follow the
onscreen instructions. You can ignore the message about the config directory for now.
You will need your MySQL root database password. In the servers section, click new
on the Server button and enter the password for root under the Authentication tab.
Follow the guides on screen to get the most up-to-date
versions and information on the best practice.
Once you are complete, you can navigate your browser to the virtual directory,
http://raspberrypi/phpmyadmin, and log in with your root credentials. The first
thing you should do is set up a new user.
Installing SQLite
SQLite3 is a self-contained, easy-to-install, lightweight transactional database. The
product's website boasts that it is the most deployed database in the world. As
we know from Wikipedia, it is actually the most deployed database on embedded
devices, which still leaves MySQL as the most used database. None of this really
matters to us because both these databases are very good at what they do, except
that SQLite is a better choice if you are looking for much better performance on your
Raspberry Pi 1:
sudo apt-get install sqlite3 php5-sqlite
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Chapter 4
We will be using phpliteadmin, a single-file administration utility made specifically
for SQLite versions 2 and 3. Also, create a new subdirectory for phpliteadmin. Note
that the Google code is closing and the package may be moved to GitHub soon. You
can search the Internet if the link doesn't resolve:
sudo mkdir /var/www/phpliteadmin/
sudo mkdir /var/www/phpliteadmin/web
cd /var/www/phpliteadmin/web
wget https://phpliteadmin.googlecode.com/files/phpliteAdmin_v1-9-5.zip
sudo unzip phpliteAdmin_v1-9-5.zip
The easiest way to get phpliteadmin working locally is by running it on its own
dedicated port.
Create a new virtual host file sqladmin with the following content:
server
{
listen 81;
root /var/www/phpliteadmin/web/;
index phpliteadmin.php;
location ~ \.php$
{
fastcgi_pass
unix:/var/run/php5-fpm.sock;
fastcgi_index phpliteadmin.php;
include
fastcgi_params;
}
}
Reload nginx and navigate to http://raspberrypi:81. The default password is
admin. At this point, you will get an error message saying that there are no databases
and the directory is not writeable.
SQLite creates flat files that contain all the data, and you can manage where you
would like to keep these files. There is no server managing these files, and any
SQLite-compatible client can connect to these files.
You can create a test database in /var/www/phpliteadmin/web using the SQLite3
command line:
sudo sqlite3 test.db
BEGIN;
CREATE TABLE temps (theDate DATE, name TEXT);
COMMIT;
.exit
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Refresh the web page where you navigated to phpliteadmin. You will see a new
layout with a list of databases on the left-hand side. If you made the directory
writeable, you can also create new databases.
It is highly recommended not to allow access to this virtual
website from the Internet as there are no security features
implemented.
Summary
In this chapter, we covered how to create various basic websites running on .NET or
PHP hosting platforms. Nginx is truly a versatile and fast proxy server, which helps
us achieve the variety of web applications that we can provide.
We had a look at how to host .NET MVC and PHP as well as install two different
types of database engines, all running side by side in harmony.
In the next chapter, we will set up file sharing for your local network and ownCloud
for Internet-based storage.
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Setting Up the Raspberry Pi
as a File Server
Windows, Linux, and Mac OS X all use different file systems, and they have
different ways of sharing files across a network. On top of all this, you also get
network-specific protocols, for example, the ones that are used over the Internet.
If you are wondering which the best one is, you will never find the answer; instead,
you should use the technologies that you find most suitable for your application and
with which you are most familiar.
Connecting the external storage
The Raspberry Pi does not have a SATA interface, and the only way to connect this
storage is by using USB ports. You can further expand the amount of USB ports by
attaching a powered USB hub.
Due to the 480 MBps limitation on the USB bus, we should consider the most optimal
setup. We reserve 100 MBps for Ethernet, which should be more than enough to
stream any kind of HD video. This leaves us with 380 Mbps (47 MBps), which is fine
because we can only send a maximum of 12 MBps of data via Ethernet anyway.
If you really want to squeeze out more transfer speed, you can use a compatible
802.11n or 802.11ac wireless USB peripheral. You may achieve in excess 100 MBps
with WiFi, but there is the extra process of making sure your signal is good and that
your general environment is not occupied by any other wireless router. The most
optimistic transfer speed you can expect is about 25-30 MBps.
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Setting Up the Raspberry Pi as a File Server
Preparing the storage medium
At this stage, it is a very good idea to use an externally-powered USB hub. USBattached hard drives will need this extra power to operate properly. If you are using
a wireless adapter and any other USB peripheral, you should consider moving them
over to the powered USB hub.
Make sure that you are not using a drive with important files.
This chapter will show you how to format drives and use other
file systems. All the data on your drives will be lost.
For simplicity, in this chapter, we will be using an 8 GB USB flash drive; but the
concept is the same for USB hard drives.
Listing the available drives
In the console, you can use the fdisk command to get a list of drives, and partitions
as shown in the following command line:
sudo fdisk –l
The fdisk command will show you the names of the disks used in Linux, their full
sizes, and partitions. The drive under /dev/mmcblk is the internal SD card, and you
do not want to do anything with this device. Instead, you should always look for
drives marked /dev/sdxn, where x is usually an letter representing a physical drive
and n is a number representing the partitions of the device in ascending order.
Unfortunately, device names are not assigned in any particular order, and there is
no guarantee that the same name will be used for the same drive. This can become
a problem when you start to use two or more hard drives. The partition numbers
never change, though, and they represent the exact order in which the partitions
were created.
The following screenshot shows that the USB flash drive has come up as the /dev/
sda device, and it has 7803 MB with a FAT32 file system:
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Chapter 5
Formatting a drive
The Raspberry Pi is capable of reading and writing to NTFS, which Windows uses. It
can also read/write HFS+, which is used by Macintosh. Both these methods are fine for
the temporary attachment of removable media if you need to copy something quickly.
The NTFS and HFS+ file systems are not native to Linux, and they take a lot of
overhead to convert data between what Linux understands and what the other file
systems understand. Some unexpected errors might occur and cause loss of data,
which nobody wants!
Ext4 is the preferred storage file system in Linux. Media mounted using this file
system in Linux is really fast and reliable. There are ways to use it on Mac OS X and
Windows, but this is not the goal of this chapter. You should commit to using the
media as long-term storage that will stay connected to the Raspberry Pi.
We first need to prepare hard drives by wiping them back to a clean state.
A word of warning is that this step will destroy all data on the
target drive.
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Setting Up the Raspberry Pi as a File Server
This command will quickly remove everything from your hard drive, including
partitions and boot sectors. Be sure to use the correct device name that you saw in
fdisk. In this case, it is sda, but you need to double check this on your Raspberry Pi
as it maybe different. This can be done using the following command:
sudo dd if=/dev/zero of=/dev/sda bs=512 count=1
Creating a EXT4 partition
We will create a new partition using fdisk. I want to use the entire drive and
defaults that fdisk provides. You can use the m command in fdisk at any time for
more help, as shown in the following command-line snippet:
sudo fdisk /dev/sda
n "new partition"
<enter> "Uses p as the default"
<enter> "Uses 1 as the default"
<enter> "Uses default first sector"
<enter> "Uses last sector available on drive"
w "write partition data and exit"
The last command that we will issue is used to create the EXT4 file system on the
partition on sda1. The –L flag in the following command line provides the name of
the partition. You can use any short name that you like:
sudo mkfs.ext4 /dev/sda1 –L nas001
Mounting the drives
Linux has a directory called /mnt where you can create mount points for various
hard drives or other network connections. There is also a directory called /media
where you can mount drives. This is a convention used throughout Linux so
that people have an idea of how to organize all these files. These are just normal
directories; and if you wish, you can create your own directory called /nas, and you
can mount all your drives associated with Network Attached Storage (NAS) there.
I will create a directory called /nas and mount my USB drive here. Then, I will create
a subdirectory called USB001. We will also create directories that we will use for
sharing, as shown in the following command-line snippet:
sudo mkdir /nas
cd /nas
sudo mkdir USB001
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Chapter 5
sudo mount -t ext4 -v /dev/sda1 /nas/USB001/
cd USB001
sudo mkdir public
sudo mkdir work
Remounting a disk after reboot
The quickest way to get your drives remounted after a reboot is to add a few lines
to the fstab file, which controls the file system configuration and can be found
at /etc/fstab.
Simply add the following lines. The first part is the partition, and the latter part is the
mount point. You need to adjust these into your hardware. The final options are used
for automounting. Do not change these options:
/dev/sda1 /media/USB001 auto noatime 0 0
Accessing files
We will go over several ways of allowing access to files on the Raspberry Pi, the
network, and the Internet. You should choose the method that suits you best, as
enabling more than one way makes it easier to compromise your system over
the network.
The FTP service
The File Transfer Protocol specification was originally published in 1971, but we
currently use a specification from 1985 that everybody should really start moving
away from. FTP uses port 21.
A much newer specification, known as Secure FTP (SFTP), supports the IPv6 and
Secure Socket Layer (SSL) encryption. Installing FTP will just be a waste of time as
OpenSSL (SSH) comes with built-in support and is enabled by default to use SFTP.
SFTP generally uses port 22, which is the same port as SSH.
You should create and use a separate user for the SFTP access. I will demonstrate
how to connect to your Raspberry Pi with two popular clients using the root account
for simplicity.
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Setting Up the Raspberry Pi as a File Server
Connecting with FileZilla
FileZilla is open source and can be run on Windows, Mac OS X, or Linux.
Download and install it on your computer. We connect to the Raspberry Pi
using the following steps:
1. In the Host field, enter the IP address or the DNS name of your Pi;
2. In the Username field, enter the name of the user on the Pi. For example,
root.
3. In the Password field, enter the password of this user.
4. In the Port field, enter the name of the port as 22. This tells FileZilla that you
want to connect using SFTP.
The following screenshot will show how FileZilla is connected to our Pi:
Connecting with WinSCP
WinSCP is the client preferred by all Windows users who need to connect to any
Linux box running the SSH or SFTP server.
WinSCP also offers Secure Copy Protocol (SCP), which is not specified by any
standard. It uses Secure Shell for data transfers and the same authentication method.
Go to http://winscp.net/ and find the [Go to Download page] link from where
you will get the installer or portable binary.
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Chapter 5
Just like with FileZilla, you will enter the hostname, username, and password. You
can use SFTP or SCP as shown in the following screenshot:
The Samba service
Samba is an implementation of the SMB/CIFS networking protocol, which is mostly
used on computers running Microsoft Windows. It is basically a way of allowing a
Windows computer to connect to Linux systems and access their shared files or printers.
It is not created by Windows and was originally developed by Andrew Tridgell.
If you want to share media from Linux with other Windows computers on your
network, Samba is the best software option.
Installing and configuring Samba
You need to install Samba and a common library that is used by Samba using the
following command line:
sudo apt-get install samba samba-common-bin
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Setting Up the Raspberry Pi as a File Server
You can then navigate to /etc/samba and edit the smb.conf file. On a private
network for personal use, you may skip any step that requires the use of passwords
to mount network shares. In an exposed or production environment, always use
authentication.
If you do not like to put security on internal network shares, then this is perfectly
safe. Since these files cannot be accessed from the Internet, you may just want to
browse your network freely and copy or move files around without the extra pain of
entering passwords.
By default, Samba is set for anonymous (unauthenticated) access. To change this,
scroll down and uncomment the security = user line by removing the preceding
#. This will tell Samba to authenticate against the users that you have created.
We will quickly create a user for the purpose of demonstration as there is an
extra step required to add the user to the Samba authentication list. The following
command-line snippet is an example of creating a system user to access Samba:
sudo useradd bond007 –m –G users
sudo passwd bond007
sudo smbpasswd –a bond007
Network shares
At the bottom of the smb.conf file, we will add two shares, as shown in the
following command-line snippet. One account is for guests without authentication,
whereas the other account will only be accessible by our new user—James Bond:
[public] comment = Media share
path = /nas/USB001/public
force user = "root"
read only = no
guest ok = yes
public = yes
[work]
comment = Work share
path = /nas/USB001/work
valid users = "bond007" #or @users to allow the group users access
force group = users
read only = no
writeable = yes
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Chapter 5
Samba can be quite difficult to understand in terms of permissions. Let's start off
with the public share. You will notice that we put a line in smb.conf that says force
user = "root". We do this because we created the public directory as root user,
so the permissions applied to the directory and all the files to be created later can
only be for the user root! So, we tell Samba to imitate guests, as root, so that they can
read/write as the root user.
The same will apply for the user James Bond and his directory. If you have created
the work directory as the root user or Raspberry Pi, even James Bond will not be
allowed to write new files. To overcome this problem, you can simply change the
owner of the folder by typing the following command line:
chown bond007:users /mnt/USB001/work
You can also assign a directory to an entire group by replacing bond007 with users.
The command will look like chown users:users. This means that anybody in the
group can write and delete files on this folder now.
The configuration file has many advanced features, and I recommend reading the
online manual to learn more about security, sharing printers, and even how to get
Samba to act like a Windows domain server!
You can now use any Windows computer to browse the network and access the
newly created shares.
AFP for Macintosh
Samba also works with Macintosh, but Apple has its own networking protocol called
Apple Filing Protocol (AFP). There is software that you can install on the Raspberry
Pi so that your Macintosh computers can detect the Raspberry Pi.
Installing and configuring Netatalk
Installing Netatalk has become really easy as most of the configuration is set up by
default. At the time of writing this book, the version used was 2.3.3:
sudo apt-get install netatalk
Within 30 seconds, you will see your Raspberry Pi pop up in the shared section on
your Macintosh. The default directory that is shared is the home directory of the user
that you log in as, for example, user Pi.
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Setting Up the Raspberry Pi as a File Server
Shares and Time Machine
We will create a few entries to use your external drive for the shares that you need,
and this version of Netatalk also supports Time Machine.
You will need to edit this file to customize some of the settings as follows:
/etc/netatalk/AppleVolumes.default
#Ammend default to look like this
:DEFAULT: options:upriv,usedots,rw,tm
#Add this to end of the file
/nas/USB001/public "Public"
/nas/USB001/work "James Bond"
Read the configuration file for more options and adjusting security. After saving, you
must restart Netatalk using the following command:
service netatalk restart
BitTorrent Sync
All the bad things that you may have heard about torrents were primarily caused
by private companies who were deliberately placing infected files to try and
track users sharing copyrighted material or malicious users who were after your
personal details.
Sync is not a public network; it only uses the revolutionary peer-to-peer technology
from conventional torrents, which allows you to share an unlimited amount of data
with an unlimited number of computers. Files are not stored on the cloud. They are
stored on all the computers that have BTSync installed on them, and you can control
who has access and where these files will be stored. BTSync includes file versioning,
sharing with mobile phones, LAN synchronizing, and delta updates. It also allows
massive file transfers of gigabytes without any problem as long as your file system
can support such large files.
Installing BTSync 2
At the time of writing this book, there were a few repositories that kept this package
with startup scripts. A word of warning: do not trust sources other than the ones
that are enabled by default. People can easily alter code and place their own version
of the binary with some nasty backdoors. Go to the official website, or use the links
provided by the official website.
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Chapter 5
We will create a new directory, download the ARM version of BTSync, and extract it
as shown in the following command-line snippet:
mkdir ~/.btsync && cd ~/.btsync
wget http://download-cdn.getsyncapp.com/stable/linux-arm/BitTorrent-Sync_
arm.tar.gz -O btsync_arm.tar.gz
tar -xvf btsync_arm.tar.gz
We will create a service file. In /etc/init.d, create the btsync file and copy the
following text:
#! /bin/sh
# /etc/init.d/btsync
#
# Carry out specific functions when asked to by the system
case "$1" in
start)
/opt/btsync/bin/btsync --config /opt/btsync/bin/btsync.conf
;;
stop)
killall btsync
;;
*)
echo "Usage: /etc/init.d/btsync {start|stop}"
exit 1
;;
esac
exit 0
We need to set correct permissions for the new file:
sudo chmod 755 /etc/init.d/btsync
sudo update-rc.d btsync defaults
sudo service btsync start
BTSync will now start every time your Raspberry Pi 2 reboots. You can check out
the configuration file at /opt/btsync/bin/btsync.conf but the defaults work
pretty well.
You can now navigate a browser on the same network to your Pi's address at
http://raspberrypi:8888/gui.
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Setting Up the Raspberry Pi as a File Server
In the GUI, add the directory on the hard drive. Now, install the application on
your Mac OS X, Windows, Linux machine, or smart phone. Use the GUI to share
directories between users. It can detect machines on the same network, which
increases the speed of synchronization.
Sync tries its best to configure ports, and it uses protocols to communicate over the
Internet. In theory, you can now call your friend on the phone, ask them to install
Sync, and share the directory via an e-mail. They will now start seeing the same files
as you.
BitTorrent Sync 2 uses external servers for tracking purposes, but no
actual files are stored on them; there is no public access to the tracker
files.
BitTorrent Sync claims to use SRP for mutual authentication and
Perfect Forward Secrecy in which all data is then encrypted with
AES-128 Counter Mode and unique session keys. It is a very complex
way to ensure nobody can guess your key, not even BitTorrent. It is
all dynamically generated on the fly, and then clients negotiate more
keys during transfers. This sounds really good, but you will have to
take them on their word as the project is closed source.
The hardware RAID
The Raspberry Pi does not have a SATA controller on board, and there is no way to
attach extra hard drives except via USB ports. The cool thing is that you can get a
USB RAID controller. This makes file storage on the Raspberry Pi a very attractive
option. Technically, the peripheral needed here is called the USB SATA multiplier.
Configuration
There is no one-step guide to configuring these multipliers. Some need to be
configured using software in Windows or Linux, while others may have DIP
switches that configure the multiplier to a specific configuration.
Addonics is a well-known and fairly easy-to-source multiplier. You will need to
search around on the Internet, online auctions, and shops for it. The prices are
around the same as the Raspberry Pi but if you are looking for redundant storage,
then these are the cheapest options you will find.
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Chapter 5
Massive storage
If you are looking to create really massive storage, you can easily daisy chain a
multiplier with another, sometimes up to three or four times. Recently, Addonics
developed another device that can be daisy chained infinitely!
Let's assume that we can daisy chain up to three levels, and we use 2 TB hard drives.
We configure all the multipliers to span data across all drives with no redundancy;
that is, five times five, times five. We end up with 125 usable SATA ports and a total
of 250 terabytes of storage. This figure is highly impractical for home users because
all these hard drives consume a lot of power. There are some people who have hard
drive rigs such as these at home, so I would think using six multipliers to achieve 25
SATA ports would be a completely viable and cheap option for some readers! The
following figure is a simple example of how to replicate one SATA port into five
more ports using SATA port multipliers:
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Setting Up the Raspberry Pi as a File Server
Redundant storage
We all have lost important data way too many times in our lives, so you should
consider redundancy over massive storage. We can use a set of four 1 TB hard
drives that are configured in RAID 5 + S. This gives us 3 TB of usable space. Also, if
any one hard drive crashes, you can just replace it quickly and all the data that we
resynchronize will be stored without any loss. The following is a figure explaining
each feature of a SATA Port replicator:
Summary
This chapter demonstrates that the Raspberry Pi is capable of doing anything that
a normal computer or server can do. It is capable of sharing files with various
platforms. You can connect to the Raspberry Pi using the latest secure FTP. It is
capable of storing a great amount of data using some clever hardware add-ons.
In the next chapter, we will set up various gaming servers.
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Setting Up Game Servers
As great as it would be to run a Counter Strike server on Raspberry Pi, it is just not
possible due to the high requirements of running such game servers. Mostly, this is due
to the shortfall of RAM, but some servers also require powerful processors to deliver
low-latency performance for all players, which could be up to 24 players per game.
In this chapter, you will be introduced to open source games that have been developed
by people with a passion for a particular genre of games. These games were reverse
engineered, built from scratch, or just became popular due to their simplicity.
Updating to Jessie
At the time of writing this book, the main distribution for the Rasbperry Pi was
still Debian Wheezy. Debian Jessie was added around June 2013 for testing on the
Rasspbery Pi but is already used on desktop machines. As of April 2015, there seems
to be a stable version for the Raspberry Pi. A lot of game server packages were
updated only in Jessie because of newer dependencies.
You can upgrade the entire Raspberry Pi to Jessie, but you are advised not to do this
until the official image is released. Instead, we will install selected, specific packages
from Jessie while keeping the entire distribution stable in Wheezy. These steps can be
skipped if you are already using Jessie.
Selective settings
We can add the following two lines to /etc/apt/sources.list:
deb http://mirrordirector.raspbian.org/raspbian/ jessie main contrib
non-free rpi
deb http://archive.raspbian.org/raspbian jessie main contrib non-free
rpi
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Setting Up Game Servers
The next step is to tell aptitude to use the wheezy repository for normal updates and
that you would like to use Jessie from time to time. These settings should be typed
into the file found at /etc/apt/preferences. Create this file if it does not exist:
Package: *
Pin: release n=wheezy
Pin-Priority: 900
Package: *
Pin: release n=jessie
Pin-Priority: 300
Package: *
Pin: release o=Raspbian
Pin-Priority: -10
After adding these settings and saving the files, run sudo apt-get update.
We will be using apt-get with an extra switch to use the new packages. You should
only use this switch when it is advised. Upgrading core packages could result in
unstable behavior. The syntax we will be using is as follows, where <package> will
be replaced with the game package that we require in the following paragraphs:
sudo apt-get –t jessie install <package>
Game servers
We will only be focusing on running the server parts of games that do not require
desktop interaction. Instead, you run the client on another computer and connect to
Raspberry Pi. Some clients can run on Pi's X desktop, and they would do reasonably
well on the Raspberry Pi 2 but might not be very pleasant.
OpenTTD
OpenTTD is a reimplementation of the original Transport Tycoon made by
MicroProse. The game is dangerously addictive, and adding Internet play to
the mix can give you an extra competitive edge.
You have to have a passion for logistics, strategy, and real-time simulation to enjoy
this game. The goal is just something to do with controlling trains and trucks as
efficiently as possible and make profit while transporting cargo.
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Chapter 6
Installing OpenTTD
The latest package is kept only on Jessie:
sudo apt-get –t jessie install openttd
Several libraries will be installed during this time. You may be presented with a blue
screen, which asks you if you want to restart some services in order to complete
the package installation. It is safe to agree to this. This can take several minutes
to complete.
Configuring OpenTTD
The configuration file called openttd.cfg can be found at ~/.open. It contains a few
hundred settings that you can tweak according to your preferences, but some of the
important ones are as follows:
• lan_internet: This sets the condition for the LAN access. For lan0, allow the
Internet, and for lan1, use LAN only.
• server_name: This is a unique name to identify the server on the Internet.
• server_advertise: We set this to true so that it will be visible on the
server list.
• server_bind_ip: We set this to 0.0.0.0; this allows the address to bind to
any network.
• server_port: For this, we keep the default value; this is how other people
from the Internet will connect over to the network.
To allow people to connect from the Internet, you should forward
the 3979 and 3978 ports to the Raspberry Pi in your router.
Start the server with the following options:
./usr/games/openttd -D
Playing OpenTTD
You can now install and run OpenTTD on other computers and invite some friends
to join you.
Click on Multiplayer, and select Internet if you have forwarded the ports for the
game. Click on find, and a list of servers will be displayed.
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Setting Up Game Servers
Freeciv
"This is a free and open source empire-building strategy game inspired by the
history of human civilization."
– Freeciv
The game reminds me of Civilization by Sid Meier. Its user interface is very similar,
but once you start playing the game, you will notice a lot more features and
possibilities that are built into the game.
Installing Freeciv
We can install the server from the Raspberry repository:
sudo apt-get –t jessie install freeciv-server
Several libraries will be installed during this time. You may be presented with
a blue screen, which asks you if you want to restart some service in order to
complete the package installation. It is safe to agree with this. This can take
several minutes to complete.
Configuring Freeciv
The default settings are good enough for you to play straight away. You can start the
server by typing the following in the console:
freeciv-server
The server should not be run with the sudo command or as the
root user but as a normal unprivileged user.
This will actually present you with another console provided by the freeciv server.
You can adjust settings of the server by typing in commands. You can try to type in
help and press Enter.
If you would like to publish your server to the online community, you need to
forward port 5555 to the Raspberry Pi through your router, and then start the server
with the extra command line called --meta.
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Chapter 6
Playing Freeciv
You can now install and run freeciv on your computer. If you are running the same
versions of the server and client, you will see it in LAN.
OpenArena
OpenArena is a free, first-person shooter based on the Quake 3 engine. It aims to be
a clone of Quake 3, but it replaces propriety content with brand new features.
Installing OpenArena
The server installation can take up to 500 MB. Make sure you have enough free
space, and then we can install the game using the Jessie repository:
sudo apt-get -t jessie install openarena-server
Several libraries will be installed during this time. You might be presented with a
blue screen, which asks you if you want to restart some services in order to complete
the package installation. It is safe to agree with this. This can take several minutes to
complete.
Configuring OpenArena
If you would like to share your server on the Internet, you should open and forward
UDP ports 27960 and 27950 on your router. Go through the settings found at
/etc/openarena-server/server.cfg:
• set dedicated 2: We use 2 for the Internet while 1 (default) is LAN
• sv_hostname "Raspberry Pi": This is used to set the name of your server
• sv_master1 "dpmaster.deathmask.net": This sets the Internet server that
keeps lists
• sv_maxclients 16: This is the maximum amount or the number of clients
that are allowed to connect
• capturelimit 8: This is used to set the capture limit in CTF
• timelimit 15: This is used to set the time limit
• fraglimit 35: This is used to set the frag limit
• g_motd "This Pie is delicious!": This is used to set the message of
the day
• g_gametype 0: This is used to set gametype to Free for All; it is also
known as Deathmatch
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www.allitebooks.com
Setting Up Game Servers
You can find hundreds of extra settings on the OpenArena Wiki. Remember that the
server must not be run as root.
The OpenArena server runs as a service. We should stop the service and run it on a
console to make sure that everything runs fine. Once you are happy that everything
is configured properly, you can start the service again:
sudo service openarena-server stop
/usr/games/openarena-server +exec /etc/openarena-server/server.cfg
Playing OpenArena
The game can be played on Windows, Mac OS X, or Linux. You should go to the
website for platform-specific clients.
Minecraft
Minecraft is a sandbox indie game where you are in control of a person that
can build anything you imagine. There are complex blocks that can be used or
programmed to do various server-side calculations. If you would like to see the
complete potential of Minecraft, you should visit BitVegas. This will be more difficult
than the other servers as we need to install and configure a lot of dependencies.
Installing the Java Hard-Float
We will need to go to https://jdk8.java.net/download.html, accept the terms,
and copy the link to the Linux ARM 32bit for this. Now, we need to download the
file, ignoring any certificate problems:
sudo wget --no-check-certificate <URL>
Then, enter these lines into the console and replace <filename> with the latest file
you that have downloaded:
mkdir -p /opt
sudo tar zxvf <filename> -C /opt
sudo /opt/jdk????/bin/java –version
You can start typing the filename and then press Tab. This will
autocomplete the filename or display a list of similar names for
your convenience.
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Chapter 6
If you get a response from the version command line, then you now have Java
Hard-Float installed on your Raspberry Pi.
Installing the Minecraft server
Minecraft servers are actively developed by various crowds, and there are many
configurations to choose from. Spigot is a high performance Minecraft server
implementation, and we can install it with the following command:
cd /home/pi
sudo wget http://ci.md-5.net/job/Spigot/lastStableBuild /artifact/SpigotServer/target/spigot.jar
# This is the command line use on Pi 2 1GB ram
sudo /opt/jdk1.8.0/bin/java –Xms512M –Xmx992M -jar /home/pi/spigot.jar
nogui
#This is the command line use on Model B with 512 ram
sudo /opt/jdk1.8.0/bin/java -Xms256M -Xmx496M -jar /home/pi/spigot.jar
nogui
It takes about 10 minutes to start up for the first time. Once it is ready, you can log on
locally from another machine and explore your new world. You should exit shortly
and configure the server for performance.
Configuring Minecraft
To allow players from the Internet to connect, you will need to open and forward the
port called 25565 to the Raspberry Pi from your router.
These are the settings that seem to be best for running on the Raspberry Pi. You can
adjust them as you go along:
server-name=Raspberry Picraft!
motd=Pie is Delicious
allow-flight=false
spawn-monsters=true
generate-structures=true
enable-query=false
enable-rcon=false
level-name=world
spawn-protection=16
online-mode=true
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Setting Up Game Servers
difficulty=1
gamemode=0
spawn-animals=true
Setting Up the Game Servers
view-distance=4
level-seed=
hardcore=false
snooper-enabled=false
level-type=DEFAULT
pvp=true
texture-pack=
max-players=20
server-ip=
max-build-height=240
spawn-npcs=true
server-port=25565
white-list=false
generator-settings=
allow-nether=false
Playing Minecraft
To connect to your server, you will need to put your Raspberry IP address in the
network settings. If you would like other people to join from the Internet, you
should read Chapter 2, Preparing a Network, to learn how to set up dynamic DNS.
Summary
In this chapter, you learned how to use another non-default Jessie repository and
how to set up various gaming servers on the Raspberry Pi. You also learned how to
install OpenTTD, Freeciv, and OpenArena from aptitude. We covered how to set up
a high-performance Minecraft server using Java Hard-Float.
In the next chapter, we will be setting up live video streaming.
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Streaming Live HD Video
In this chapter, we are going to use the official HD camera module designed by the
Raspberry Pi Foundation. Thanks to the new quad core processor and the author of
UV4L, we can now stream a video directly into a browser with low latency.
Before starting this chapter, you should have the camera module installed and
enabled as described with the instructions included with the camera module. It is
recommended to have 256 MB GPU RAM allocated.
This chapter is only suitable for the Raspberry Pi 2 or newer with the quad processor
or better.
Installing UV4L
UV4L is a userspace webcam driver specifically designed for the Raspberry Pi. It
also includes some other features that will be discussed in this chapter. U4VL is
custom code that is written and developed by Luca Risolia, who runs the website
http://linux-projects.org. We will add his repository to get the UV4L driver:
curl http://www.linux-projects.org/listing/uv4l_repo/lrkey.asc | sudo
apt-key add -
Add the following line to /etc/apt/sources.list:
deb http://www.linux-projects.org/listing/uv4l_repo/raspbian/ wheezy
main
If you have not yet run rpi-update, then it is recommended
to do it now. The UV4L driver requires the latest foundation
kernels and modules to install properly.
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Streaming Live HD Video
Now we need to update the repository list, and then we can install the UV4L driver.
We will do these with the following commands:
sudo apt-get update
sudo apt-get install uv4l uv4l-raspicam
sudo apt-get install uv4l-server uv4l-raspicam-extras
The UV4L driver makes it really easy to stream video from the
Raspberry Pi. Consider supporting Luca by visiting his website
and donating to his cause or purchasing a serial key for the
overlay module that is described later in the chapter.
Configuring the UV4L-RaspiCAM
The configuration file can be found at /etc/uv4l/uv4l-raspicam.conf and is used
to configure the initial video stream. There are default settings that are used, and the
following bullet points are settings found within the file that you may be interested
in changing manually for your own use.
These are some typical settings that you may want to use if
capturing a stream using VLC. The driver is adaptive and will
change configurations if you request MJPEG stream, or it will start
a WebSockets stream from the browser, technically allowing you
multiple streams. Multi-streaming is experimental, though.
Here are some typical settings:
• Encoding:
Streaming: H264, mjpeg, jpeg, yuv420
Specialist: nv21, yvu420, rgb565, rgb565x, rgb24, bgr24, rgba.
• Framerate:
0 sets auto
30 at 1080p
60 at 720p
90 at VGA.
• Bitrate: 17000000 (default value)
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Chapter 7
• The Intra-period: This is used for H264 only; if you experience artifacts in the
stream, try adjusting this value. Usually, artifacts are caused by lost frames
and poor network performance. The lower this value, the more bandwidth is
used. A good start is FPS / 2.
• Quality:
This applies to JPEG and MJEP streaming only
85 is the default value.
• * text overlay: Uncomment the two properties as this will be required later in
the chapter.
• * no preview: If you have a monitor connected to HDMI, you will see the
original stream preview. Uncomment this if you are experiencing Raspberry
Pi reboot with a 1 A power supply and Wi-Fi.
Most of these configuration settings can be altered through the web interface by
navigating to http://raspberrypi:8080. The options with the * mark must be
configured in the configuration file, and UV4L must be restarted.
Installing WebRTC
Web Real-Time Communication (WebRTC) is a protocol that allows modern web
browsers to establish a peer-to-peer link to exchange data. UV4L uses WebRTC to
create a socket to the Raspberry Pi and receive a live H264 video stream, eliminating
the need for transcoding and allowing us to watch a high-quality, low-latency video
directly in our browser.
To install the WebRTC module for uv4l-server, we just need to issue one command
and restart UV4L:
sudo apt-get install uv4l-webrtc
sudo service uv4l_raspicam restart
WebRTC streaming
Please be aware that UV4L WebRTC streams in an adaptive bitrate and resolution.
The bitrate and resolution streamed to the client will adaptively adjust based on the
connection quality. This means that any configuration that you have applied will
not apply to WebRTC streams, but the overlay will still work. It may also disconnect
other streams that do not use WebRTC.
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Streaming Live HD Video
You can now navigate to http://raspberrypi:8080, and you will be presented
with a screen similar to the following:
You can click on audio/video stream via WebRTC. Then, on the next page, click on
the start button. It may take a few seconds to establish a link, and if everything goes
as planned, you will know see a live stream from the Raspberry Pi camera.
With the Raspberry Pi 1, it was extremely complicated to set up a stream similar to
this one, leaving almost no resources left on the Pi at all. The WebRTC module is
truly a time saver in terms of streaming from your Raspberry Pi.
Real time HTTP streaming
To configure the HTTP stream, you can click on the Camera Control Panel link on
the UV4L web page and set the format and other options you would like.
Alternatively, if you don't want to access the webpage, you can just configure the
raspicam configuration file as you need it, and then you can use the corresponding
URL in VLC or a third-party app to capture the stream:
• HTTP/MJPEG: http://raspberrypi:8080/stream/video.mjpeg
• HTTP/Raw H264: http://raspberrypi:8080/stream/video.h264
• HTTP/JPEG: http://raspberrypi:8080/stream/video.jpeg
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Chapter 7
To receive a H264 stream using VLC, I have found that tweaking some of the plugin
settings worked best for me:
1. Click on Tools | Preferences.
2. Click on All in the Show settings panel in the bottom-left corner.
3. Click on Input / Codecs | Demuxers.
4. Change the demux module from the Automatic to H264 video demuxer.
5. Click on Demuxers | H264.
6. You will notice that it is set to 25 frames per second. Unfortunately, changing
this value does not work as expected. You should rather change your
configuration on the Raspberry Pi to stream at 25 frames per second.
7. On the Raspberry Pi, choose a suitable bit rate for your stream. On the LAN,
this maybe the default, but on Wi-Fi, I suggest you try lower bitrates.
This configuration works best for higher quality streaming. It is necessary to change
the VLC demuxer to H264 because it does not seem to be able to recognize the format
on its own. You can also specify an additional option of :demux=h264, but I find that
strictly setting the demuxer to H264 works better.
We also need to adjust the frame rate on the Raspberry Pi to 25 fps to match the
default in the H264 module in VLC. Adjusting the frame rate in the module on VLC
to 30fps did not help. The reason behind adjusting the frame rate is that I noticed
strange artifacts on moving objects. This suggested bandwidth problems, but it even
happened on the LAN.
I finally found this solution and realized that the Raspberry Pi was sending 30 fps
while the demuxer was decoding at 25 fps, causing the key frames to be out of sync.
As strange as this may sound, it really does produce a good quality stream, albeit
with about 1+ seconds of buffering.
If you are experiencing no video, lots of artifacts, or long lags, refer to Chapter 2,
Preparing a Network on how to run the iperf test to make sure you have good
enough bandwidth. Bandwidth problems may also be caused by a poor power
supply, especially if you are using a wireless adapter.
Web conferencing
In the latest version of UV4L, there is an interesting new feature for web
conferencing with audio and video. This feature is built into the webrtc module, and
no extra configuration is necessary.
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Streaming Live HD Video
Any WebRTC compatible device, such as a smart phone, note book, or standard
desktop, with a modern browser can join into the conference by going to http://
raspberrypi:8080/conference. This will work inside your LAN, but if you would
like to allow connections from the Internet, you need to provide the correct IP
address in the Signaling Server Field and open the necessary ports.
This works purely as a server and does not use the Pi's camera, but you can join the
conference from your Raspberry Pi from within the X client and a browser. If you
want to use audio on the Raspberry Pi, make sure you have pulseaudio installed
and a compatible USB sound card with a microphone.
Streaming the X desktop
It is also possible to stream your actual X desktop using the UV4L driver. Consider
it something like screen casting, similar to Miracast. If your smart TV's browser
supports WebRTC, you can simply enter the URL and have a wireless video feed of
the desktop on the TV.
To use this feature, we need to install an extra module.
sudo apt-get install uv4l-xscreen
You can then use raspi-config to enable boot to desktop/scratch to start up
on the boot. As mentioned in the WebRTC section, the only caveat at the moment
is that this will only work with a specific resolution. Other resolutions may be
supported in the future. You will need to edit your /boot/config.txt file as follows:
framebuffer_width=640
framebuffer_height=480
framebuffer_depth=32
framebuffer_ignore_alpha=1
You can now log into your Raspberry Pi over SSH and issue the following command:
uv4l --driver xscreen --auto-video_nr --display :0 --framerate 10
--server-option '--port=9000'
Ignore all warnings. This command starts a new UV4L server and creates a device
called /dev/video1 that can be used with the same commands as described in the
real-time HTTP streaming section. It creates the webserver under port 9000. Port 8080
still works and can continue to stream your webcam while streaming the X video
separately.
You can view the video transmission at: http://raspberrypi:9000/stream/
webrtc.
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Chapter 7
Text overlay
Text overlay is a feature that allows you to superimpose text lines onto video frames
without any transcoding. The UV4L driver works extremely well with HD streams and
framerates higher than 30, and supports mjpeg, H264, yuv420, and other video formats.
When enabled, the image width and height should be a
multiple of 16. For 1080p you would need to use 1920 x 1088,
720p would be 1280 x 720, and so on.
At the most basic level, text is read from a JSON-formatted file, which contains
properties for each line's position, color, thickness, and scale. The default configuration
file will display the video frame rate as it is being transmitted. The configuration file
gets loaded when the camera is started for the first time, but it can be updated with a
specific command, making heads-up displays (HUDs) a practical reality.
To enable the text overlay, you need to start the driver with the following /etc/
uv4l/uv4l-raspicam.conf configuration before loading the camera page for the
first time. You cannot enable this feature if there is already an ongoing stream:
text-overlay = yes
text-filename = /usr/share/uv4l/raspicam/text.json
The text.json file contains a sample of all the options that are available to you.
It is a good idea to copy this file to /home/pi.
If you plan on updating the file frequently, it is recommended to
store the file in /tmp as the file will actually be stored in RAM.
After restarting the uv4l_raspicam service, you will now see some sample overlay
text on your video stream.
You can edit the text.json file and execute the following command in the console
for the overlay text to be updated:
v4l2-ctl --set-ctrl=text_overlay=1
This is a very basic approach to updating the overlay on your video stream, for
example, running a separate program you wrote that will overwrite the file every so
often and issue the refresh command.
Using this approach, you will not be able to update the overlay any faster than 1
second at a time. If you would like to achieve real-time overlay updates, refer to
The HUD sample section.
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Streaming Live HD Video
More details about how to remove the http://www.linux-projects.org overlay
are provided further on in this chapter.
Object detection and tracking
Object detection and tracking can be turned off and on at any time. This feature only
works with the yuv420, H264, and mjpeg encodings.
This feature requires more CPU overhead depending on how complex a task you are
doing. For example, on the Pi 2, you can use face recognition with 640 x 480 at 15 FPS
with some heavy CPU usage. On the Pi 1, it is about half of this:
uv4l --driver raspicam --auto-video_nr --object-detection --minobject-size 80 80 --main-classifier /usr/share/uv4l/raspicam/
lbpcascade_frontalface.xml --object-detection-mode accurate_detection
--width 320 --height 240 --framerate 15 --encoding h264
Removing the overlay watermark
I have been in contact with Luca Risolia, the author of UV4L, and he has agreed to
provide you with an exclusive deal; as the reader of this book, you will be the very
first person to know that he has agreed to provide you with a way to remove the
white http://www.linux-projects.org watermark on the 3 Raspberry Pi's that
you own!
All you need to do is send an e-mail to [email protected] with the
following details from your Raspberry Pi by executing and copying the results
of this command:
uv4l --driver raspicam --serial-number
I am sure Luca will be grateful for a small donation in return for three serial
numbers, and this will allow him to continue to create more features for this
excellent driver.
The HUD sample
As defined by Wikipedia, a heads-up display, also known as a HUD, is a transparent
display that presents data without requiring users to look away from the main
activity. The origin of the name comes from a pilot being able to view information
with their head positioned up or straight ahead, instead of looking down at some
instruments.
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Chapter 7
So, to stop us from looking down into the console, I thought it would be a nice idea
to see some information about our Raspberry Pi directly on the video stream.
With some help from Luca, I have created the C++ code that allows you to update
the overlay pretty much on every frame using the UV4L API directly, which means
hardly any CPU overhead is used.
If you feel comfortable with C++11, I have provided the complete code sample on the
code download page, and you can add your own variables.
I have also provided a compiled binary with a variety of popular resource variables
that you can use easily place in the template file once, and will be updated in real
time on your stream.
Using the overlay binary
The binary requires two parameters: the source video device and the source file,
which will be referred to as the template file. The template file is exactly the same
format as text.json, but the difference is that you construct the text fields with the
inline variables listed here. It is recommended to copy your template file to /tmp/
file.tpl and provide it as the source template.
You will also need to update the uvl_raspicam.config file to point to a new
location, /tmp/text.json (not the template file), and restart the UV4L service.
A new file will be created in /tmp/text.json from which the UV4L API call will
read the replaced variables. Do not alter this file. Working with these files in /tmp is
critical for achieving the best video performance but also eliminating I/O from your
SD card, which may cause unnecessary wear during long periods of use.
In case you are wondering, you can update the template
/tmp/file.tpl file while the binary is running. The C++
binary file reads the template file using a stream open in
read-only mode with minimal locks.
Use this command line to execute the binary:
./overlay /dev/video0 /tmp/text.tpl
Inline variables
Here are some useful variables from the general Raspberry Pi resources:
• {sysnfo.cputemp}
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Streaming Live HD Video
Wireless info (the default is wlan0):
• {signfo.level}: Signal strength
• {signfo.quality}: Signal quality
• {signfo.bitrate}: Bitrate
Network bandwidth (the default is eth0):
• {nnfo.downspeed}
• {nnfo.upspeed}
A sample text line will look like this:
"ETH0 UP: {nnfo.upspeed} CPU temp {sysnfo.cputemp}"
To change the default values you need to amend the C++ file and recompile it. If
you are already going to edit the code, use the base code as an example and try
to add something else. If you have never edited C++ or any other code, just try to
understand the main class line by line, and by the time you get to the end, you will
understand the basic C++.
Compiling the overlay code yourself
The C++ code was written in the C++11 standard, and it is necessary to install G++
version 4.8 to be able to compile this code. No extra libraries, such as libboost, are
required for this sample:
sudo apt-get install g++-4.8
Once you have installed the latest G++, you can then simply compile the main
code file and extra code files with any changes you have made by executing the
following command:
sudo g++-4.8 -Ofast -std=c++11 *.cpp -o overlay
Luca has also provided a text-scrolling example that can be downloaded from
http://www.linux-projects.org/downloads/examples/uv4l-overlay.cpp, but
it requires the Boost C++ library. Unfortunately, the inclusion of this library causes
the code to take considerably longer to compile. This is why I have removed all
dependencies from the Boost library in my code; it provides a lot of extra support for
tasks and structures used in modern programming languages and is worth a try:
sudo apt-get install libboost-all-dev
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Chapter 7
If you are a Visual Studio developer, you will be happy to know that I have created
the overlay binary using Visual Studio with VisualGDB. VisualGDB allows
you to write code with C++ intellisense in Visual Studio on your desktop. It will
automagically copy your files and compile them on the Raspberry Pi over SSH.
Another great feature is that you can debug the code running on the Pi within
Visual Studio! You do not need to install any extra software on the Raspberry Pi. A
tutorial on how to start using VisualGDB is available at http://visualgdb.com/
tutorials/raspberry/.
There are other tutorials on the site you may find interesting. There is a 30-day trial
you can use.
Summary
Streaming videos is still one of the most popular search terms on the Internet for the
Raspberry Pi. There are a lot of different examples and solutions, some very complex
some very easy.
Thanks to the work put into the UV4L driver, video streaming is becoming much
easier to achieve. Compared to Raspberry Pi Server Essentials, Packt Publishing, my
previous book, this chapter has been extremely shortened due to the easy that it has
accomplishes now. Not only is it shorter, we have many more features to work with
and can enjoy HD video streaming on the Raspberry Pi 2 with the smallest amount
of effort.
In the next chapter, we will look at how to set up the Pi as a media center.
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Setting Up the Pi as
a Media Center Server
The Raspberry Pi has an HDMI output that is capable of streaming high definition
audio video, and it also supports CEC to share remote control functions. In this
chapter, we will look at how to use the Raspberry Pi as a media server directly from
the command line, displaying images and playing audio. We will briefly look at some
other solutions that people have come up with, and finally install OSMC (previously
known as RaspBMC—an XBMC media center), which uses hardware decoding and
CEC out of the box.
If you are going to use Raspbian for these examples, it would be advisable to allocate
some more GPU RAM. A recommended value is 512MB for the Raspberry Pi 2. You
can change core system settings by typing raspi-config in the command line.
Slideshows
Linux users are familiar with the command-line program called fbi (frame buffer
image viewer). We will connect a widescreen monitor or HD TV using an HDMI cable.
You should be aware that square aspect computer monitors
smaller than 19 inches or non-HD TVs are generally not
supported with HDMI output.
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Setting Up the Pi As a Media Centre Server
There is a project called HDMIPi that offers an affordable 9-inch, HD 1280 x 800 LCD
screen, which plugs into the HDMI port without any extra parts. There are other
smaller LCD screens available, but they can be quite expensive, and you need to
check compatibility.
Using fbi
On the Raspberry Pi, you can load original sized photos from high quality cameras,
but it is recommended to use a fast class 10 SD card or other fast storage. The new
quad core processor speeds up loading times considerably. On the Raspberry Pi 1, it
was recommended to downsize photos to help loading times. With the Raspberry Pi,
it is still advised to downsize, but you can easily keep the images in an HD resolution,
which is near 3 megapixels (2048 x 1536). To produce the crispest images, it suggested
to match the image resolution to the display resolution and the aspect ratio.
Use the following command lines over SSH. This will install fbi and start a simple
slideshow over SSH, but the output will be the attached monitor on HDMI:
sudo apt-get install fbi
cd /home/pi/photos
sudo fbi –T 1 –a –noverbose –t 5 *.*
fbi will now loop through all the images in the directory, changing them every 5
seconds until you stop it.
The T -1 command tells fbi to use the terminal one output (in SSH only),
which will be the HDMI port. We tell it to auto resize the images to fit the screen,
while –a –t 5 changes the image every 5 seconds, and –noverbose disables any
debugging information.
You will notice that fbi does not block the console and runs in the background. It is
possible to run fbi again, and it will not complain about another instance. However,
this may cause out-of-memory errors and unwanted behavior.
To stop fbi, we use the killall command:
sudo killall fbi
Playing videos
We can play video and audio files using OMXPlayer, which was specifically
designed by the XBMC project, and it uses hardware decoding on the Raspberry
Pi. Since OMXPlayer uses hardware decoders, it is possible for you to use any
additionally purchased video licenses.
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Chapter 8
OMXPlayer requires at least 256 MB GPU RAM to run.
OMXPlayer for video playback
Download an MP4 file onto the Raspberry Pi (for example, we can use the site
http://www.hd-trailers.net/ to find some links) and we will use OMXPlayer to
play video and sound to the HDMI port. You can also use RTMP streams directly
instead of video files. Replace the URL in wget with an existing file on the Internet:
sudo apt-get install omxplayer
cd /tmp
sudo wget http://videosite.com/filename.mp4
omxplayer –o hdmi filename.mp4
Playing audio
The latest Raspbian image comes with all the sound drivers and utilities installed.
The packages that are used belong to ALSA. The Raspberry Pi has no way to record
audio as it has no microphone jack, and the GPIO pins are all digital. To record audio
using GPIO, we need to use an A/D (analog-to-digital) device or a USB sound device
that has a microphone input.
Aplay for audio playback
The following is a pre-installed package that plays WAV files:
cd /tmp
wget http://goo.gl/Ps3paV
mv Ps3paV siren.wav
aplay siren.wav
OMXPlayer for audio playback
OMXPlayer is not just used to play videos. It also supports the playback of audio
files, such as MP3 files, and it will try to use hardware decoding if possible:
omxplayer audio-test.mp3
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Setting Up the Pi As a Media Centre Server
Using AirPlayer
There is a project called shairport that works really well on the Raspberry Pi. It does
not support videos or photos, but streaming music in it is very stable. We will need
to get the project and compile it. This will only take a few minutes:
cd /tmp
git clone -b 1.0-dev git://github.com/abrasive/shairport.git
cd shairport
sudo ./configure && sudo make && sudo make install
The files on /tmp will be deleted during the next boot, which is fine because the
binaries are now installed on the Raspberry Pi. Run the server with the following
command and the AirPlay icon will show up on your Apple devices that play music:
shairport -a 'ShairPortPi'
This will block the console, and you will see some messages pop up from time to
time about packets, but this is normal.
Using alsamixer
You can log into another SSH console and control the volume using alsamixer. The
Raspberry Pi only has one output by default, and pressing the up or down key will
make it louder or quieter:
alsamixer
Installing OSMC
OSMC is a free and open source media center, which was originally known as
RaspBMC; it is based on XBMC. In this section, we will burn a new image on the
SD card. You can either use another SD card or wipe the one you have been using
until now.
We can use a UI installer made for Windows, Mac OS X, and Linux:
1. Open your browser and navigate to https://osmc.tv/download.
2. Select the UI download link, which matches the operating system that you
will burn the network from; download it and run it.
3. Select your language and then select Raspberry Pi 2.
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Chapter 8
4. On the following screen, try and select the latest version.
Network image means that on the first boot, it will download
the latest files, so it recommended to connect a wired network
with Internet access for first boot.
The UI installer also gives us an option to install OSMC on a USB drive instead of
an SD card. If you select this option, you will need a USB storage device connected
during the first boot. You will also need a keyboard.
The first boot can take about 10 minutes to complete, after which it will reboot and
the installation will be complete.
Configuring OSMC
OSMC can be configured from the user interface, but you can still log into SSH to
install your own services or tweak some advanced settings. The default root login
and password is OSMC, and you also get a web remote if you navigate your browser
to http://osmc.local.
On the remote page, you can use your keyboard arrows to
control the user interface instead of clicking on the buttons.
Enabling other codecs
OSMC uses OMXPlayer, which was maintained by XBMC. As we know, OMXPlayer
uses the Pi's hardware to decode videos and render the GUI.
If you have MPEG-2 or VC-1 encoded files, you can simply purchase licenses and
enter codes using the OSMC interface. The H264 codec is already licensed in the
price of the Raspberry Pi. Do this by navigating to: Programs | OSMC Settings |
Pi Config (Raspberry ICON) | GPU Mem & Config and then enter your keys and
reboot the system.
Wireless configuration
You should have been able to setup wireless connection during the first setup wizard
if you had a wireless adapter plugged in. You can still configure Wi-Fi, and if your
adapter supports it, you can also enable tethering (known as an Access Point), which
is a great feature to extend your Wi-Fi range if your Raspberry Pi is connected via
Ethernet. Navigate to Programs | OSMC Settings | Network (3 CONNECTED
CIRCLES ICON)
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Setting Up the Pi As a Media Centre Server
Media sources
You can start to add the locations of the files that are stored on the USB drive.
To do so, navigate to the following options:
• Videos | Files | Add Videos
• Music | Add Music
If you have a hard drive or USB stick inserted, you will be able to browse into the
location. To access Samba or NFS, you need to type in a specific prefix before the IP
address of your NAS to specify the required protocol:
• smb://192.168.0.1/movies
• nfs://192.168.0.1/music
Using add-ons
OSMC has a single repository for add-ons, but you can also install custom add-ons.
You can find some great add-ons in the following repository:
Programs | Get More…
A lot of add-ons are getting ported to OSMC, and over time, you should find more
and more interesting programs to install and use.
On the Raspberry Pi, you can also access a limited set of OSMC App Store programs:
Programs | OSMC Settings | App Store (Shopping Cart Icon)
AirPlay
As an Apple user, you will appreciate that OSMC can be used as a target to stream
your media into:
Settings | Services | AirPlay | Allow Airplay Content
You will now find the AirPlay icon on your Apple devices.
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Chapter 8
Enabling CEC and remotes
CEC (Consumer Electronics Control) is a standardized protocol used in new
televisions, media players, and sound equipment. You need to have everything
connected using HDMI cables. In general, most remote controllers or systems allow
these functions. CEC is enabled by default, but you can change the settings as you
like. To do this, navigate to Settings | System | Input Devices | Peripherals | CEC.
If you have a smart TV using a CEC compliant HDMI cable, you should be able
to control the volume and navigate OSMC using the arrow buttons. More support
varies between devices.
You can also look at enabling other remotes in the system configuration. You may
need to manually configure Bluetooth or IR adapters to get these enabled. Navigate
to Programs | OSMC Settings | Remotes (Remote Icon).
Performance optimization
OSMC will run best on the Raspberry Pi 2, and you do not need to change
any settings.
There is a Raspberry Pi installer too, which is already tweaked for best performance
and lacks a lot of the fancy stuff, but it will play HD video.
Overclocking
Generally, it is not recommended to overclock the Raspberry Pi because it tends to
create problems with networking and stability. But if you have a good reason to
do so, then the option can be found here: Programs | OSMC Settings | Overclock
(Gauge Icon). You can select Turbo, a predefined overclock setting, or set your own
custom range.
Summary
In this chapter, you learned how to play audio, make slideshows, and watch videos
from the console. We also explored how to install a new operating system based on
RaspBMC, which is known as OSMC.
In the next chapter, we will look at how to run your Raspberry Pi using batteries.
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Running Your Pi from a
Battery's Power Source
You would typically run your server from a mains powered USB adapter. The
Raspberry Pi is very small, and unlike full desktop PCs, it can run from batteries for
an extended period of time if the battery setup has been done properly.
You may find the need to run the Raspberry Pi using batteries for remote controlled
applications, for example, weather stations in remote areas, a remote controlled car,
and similar situations.
The most common problems with embedded device are related to power. You
purchased a 2 A power supply, but one thing you cannot see is how much noise the
power supply generates.
This chapter will be short, but I will demonstrate how to create a long lasting, super
clean, 99.8% noise-free power source. This is great for wireless communications that
rely on clean and stable power sources.
Hardware requirements
If you are really serious about running your Raspberry Pi from batteries, you will
have to prepare a budget for some extra equipment. These requirements will not
clear out your bank account, but I will also include more expensive solutions and
their benefits. This chapter is based on the minimum required equipment, which I
typically use.
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Running Your Pi from a Battery's Power Source
The minimum requirements are as follows:
• A battery charging station
• NiMH battery packs
• A voltage regulator
These are the minimum parts required to get a fairly decent and safe battery
power source.
The battery charging station and voltage regulator can be reused for years to come,
and the only further expense will be new batteries or higher quality equipment parts.
The remaining chapter will use these parts as my test rig, and the estimated price of
each component is as follows:
• Charger: IMAX B6 (35 EUR/40 USD)
• Batteries: 2 x 1500 mAh 6.0V NiMH High power series (18 EUR/22 USD)
• Voltage regulator: 3 A/5 A UBEC with capacitor (4 EUR/6 USD)
Charging stations
This will be the most expensive part that you will need to acquire, but it is only a
one-off expense. The charging station that I recommend is the well-known IMAX B6.
It can charge a variety of batteries: Li-ion, LiPo, LiFe, NiCd, NiMH, as well as Pb. It
has built-in safety features; it is very reliable and compact, pretty much the cheapest
all-round charging solution to be found.
One last advantage to this charger is that you can power it using any kind of power
pack between 12V and 18V. A caveat is, though, the closer to 12V you go, the higher
the amps you need on the power brick, but it also depends on the rate at which you
are charging your batteries. If you decide to get fast charging batteries, use a higher
voltage and amp power pack. Take a look at next image:
I strongly advise that you try source a genuine product
if you would like to guarantee the longest life of your
batteries. Using imitation products maybe safe enough, but
try and reduce your top-charging limits or follow calibration
instructions to prevent over-charging. Always charge
batteries in a safe and well ventilated room away from
flammable objects and out of reach of children.
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Chapter 9
Battery packs
In my shortlist, I recommended NiMH (nickel-metal hydride) batteries because
they are the safest batteries to use. These batteries do not become volatile when
overcharged; in other words, you don't have to worry about the violent explosions
that may happen with other types of battery. Overcharging these batteries will cause
permanent damage, and the batteries must be replaced if that ever happens.
They have a fast self-discharge rate though, so they will not last long if fully charged
and stored for later use. They are best used shortly after charging them.
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An important factor is that they are pretty cheap to purchase. With the recent nano
cell NiMH technology, you can pay slightly more to benefit from even better power
output and capacities than leading Li-Po batteries. Look at the following image:
Voltage regulator
You maybe wondering why we don't just use 5V batteries to power the Raspberry Pi
and reduce the cost of extra batteries and voltage regulators.
It all depends on the same principle as electricity in your home. The power station
transports power in extremely high voltages exceeding tens of thousands of volts,
but your computer only requires 12V to run.
The answer to all of this is Ohm's law. To understand this law in the simplest terms,
you can imagine a seesaw with volts on one side and amps (the current) on the
other side. Look at the following image:
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The more volts you have, the fewer amps you need to use. The more amps you have,
the fewer volts you need to provide. Ohm's law is universal and easy to adjust, but you
still have to remember about resistance, which always works against you on each side
of the seesaw, and this is related to the thickness of the wire you are using.
Using a 2 x 6V (12V) battery pack power supply to power a 5V system, we get a
few benefits:
• We can provide higher constant power (amps) for a consistent period of time
• We can use the battery cells down to the very last volt; it will give us without
losing power to the Raspberry Pi
• It is much easier to provide peak power (bursts of high power demand),
which is great if you want to use motors or transmit high power bursts of
data, and it is more efficient to do so with higher voltages
• Generally, this is the most stable configuration in this scenario for the
Raspberry Pi
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Running Your Pi from a Battery's Power Source
Ohm's Law
The following diagram is a simplified version of Ohm's law. It demonstrates all the
calculations you need to work out a specific value, as discussed earlier. As a simple
example, if you want to work out how many Amperes you need, you find the
Amperes heading and pick a suitable equation. A suitable equation is one where you
can fill in all the unknowns on the right-hand side. Apply the calculation and there is
your answer:
Discharge curves
When a battery cell starts to deplete, the voltage it provides drops a lot faster in
the last 10% of its capacity. Looking at this graph, you can easily understand what
this curve looks like at various discharge rates. If we used a 5V battery source, the
Raspberry Pi would only run for about 60% of the batteries, power as it will soon
drop below the 4.9V required for stable operation. But if we use higher voltage cells,
we can utilize every last drop of voltage to keep the Raspberry Pi going:
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Discharge characteristics
As the voltages drop in each cell, the voltage regulator draws more power (amps)
from the batteries to keep the output voltage stable. Remember the seesaw effect and
Ohm's law? The last bit of power gets used up very quickly but constantly provides
stable output power for the Pi:
Putting it all together
To find all the extra parts, such as connectors and wires, you should visit your
nearest RC hobby shop. You can buy all the parts and crimp everything yourself, but
there are also premade wires for this exact setup.
I strongly recommend that you power your Raspberry Pi 2 via the USB connector. The
Raspberry Pi Foundation has taken extra care to create a new power filtering system
on the Raspberry Pi 2 to help stabilize the Raspberry Pi. Mostly because of all the
strange USB power supplies out there, extra filtering and protection is always good.
If you have any extra peripherals, it would be best to connect them directly to the
voltage regulator output instead of powering it from the Pi's GPIO or USB port. This
will take unnecessary stress away from the Raspberry Pi, and the voltage regulator
will easily handle higher loads.
How long will it last?
Battery capacities are measured using mAh (milli Ampere hour):
• By adding batteries in series, such as in this design, you do not gain more
capacity but more voltage
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Running Your Pi from a Battery's Power Source
• By adding batteries in parallel, you gain more capacity but stay at the same
voltage.
• Finding the best balance depends on your requirements
To properly calculate how long your batteries will run can become a very complex
calculation. You need to take a lot of things into consideration. In this design, using
a higher voltage gives us more time because the voltage regulator needs to use less
current (amps); a higher draw of charge reduces battery usability.
In an ideal world, you could say that we will be able to supply 1,500 milliamps per
hour. This is 1.5 amps for an entire hour. If you want to extend battery life, you
can add a separate battery circuit, such as the one demonstrated in this chapter, in
parallel to the existing one. So, this would give you 1.5 amps for 2 hours or 3 amps
for an hour.
In my own experience, I was able to stream an HD video over Wi-Fi to another
computer on my network for nearly 3 hours.
Summary
You learned that running on batteries can quickly become a complicated task if you
do not understand Ohm's law and some fundamental characteristics of batteries.
Using this tested design, you should be able to scale your requirements a lot more
easily now, but I encourage you to always do more research when changing certain
aspects of this design.
If in doubt, find a well-recommended RC hobby shop; the principles they use in
this type of equipment is exactly the same here, and you will have all the parts and
knowledge right there.
In the next chapter, you will learn how to install Windows IoT and create a simple
Universal Application in Visual Studio Community.
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Windows IoT Core
Windows IoT Core's main target is education and hobbyist users. It does have a GUI
stack but is limited to Microsoft's Universal App Platform (UAP), which is not a bad
thing if you are interested in developing C# applications using XAML or HTML.
You are not strictly limited to the previously mentioned technologies. Microsoft tries
to support a few other programming languages, such as C++ and Python with UAP
SDK, but also native Win32 applications or services with some limitations.
The other benefit of developing universal apps is that you can install them on any
device running Windows 10, even a full desktop. So, it is easy to distribute one
code base to the Raspberry Pi 2, Intel Galileo, or MinnowBoard for embedded
applications. Also, for remote managing console to your Windows 10 Phone, Tablet,
Desktop, or Xbox.
Windows IoT comes with a lot of criticism from the Linux community as to why
Microsoft even bothered doing all of this. Essentially, the point is not to replace
Linux or try to displace Linux users but help more people to get involved with
embedded prototyping. As a .NET developer, you will appreciate that you can
finally create apps within a smooth workflow for embedded devices using the IDE
that you love. Visual Studio, with full debugging capabilities with the ability to
embed your favorite NuGet packages on a device that will measure the temperature
of your aquarium.
As of writing this chapter, appreciate that IoT has only been
released; there are many issues that are still to be resolved
and many more features to be added, so it will only get
better from here on.
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Windows IoT Core
Getting started
To fully benefit from this chapter, you will need a Windows 7 or better desktop
machine. Windows 10 is recommended but not essential.
To create universal applications for Windows, IoT will need to install Visual Studio
2015. You can install a completely free version called Community edition. Only
2015 supports universal apps. You can also create other types of projects in the
Community edition completely free.
To get started with developing universal apps, you must have Visual Studio 2015.
You can download the Community edition for free, but you need to create a live
account and log into the account in the Visual Studio community to keep your free
subscription active.
Flashing IoT
It is recommended to use Windows 10 desktop to download and burn the IoT image
to an SD card. To get your image, you need to open https://dev.windows.com/enus/iot and click on Get started now. You can then click on the Rasperry Pi 2 and
follow the steps there.
The SD card image is distributed in an FFU format supported only on Windows 10.
To be able to burn it on an older version of Windows, we need to convert the image
into a raw image file.
Python for Linux or Windows 7 and 8
Windows 10 has a new version of the DISM binary, which is used to burn the FFU
image file types onto SD cards. In previous version of Windows, we will need to use
Python. Python is also used on Linux-based machines.
If you have python installed on your Windows or Linux machine, you can use a script
created by somebody that goes by the nick name of t0x0, and it can be downloaded
from the following location. This script works both on Python for Windows and Python
for Linux: https://raw.githubusercontent.com/t0x0/random/master/ffu2img.py
At this point, you will need to install Python 2.7 or a newer version for Windows, and
you can get the latest installation files from https://www.python.org/downloads.
Copy the FFU2IMG Python script into the directory where you extracted the Windows
IoT image. Open a command window, navigate to the directory, and use the
following command to convert the image:
python ffu2img.py Flash.ffu
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Then, you can flash the image onto an 8 GB minimum SD card from your Linux
machine:
sudo dd bs=1m if=Flash.img of=/dev/<you_SD_card>
Or you can use Win32 DiskImager to burn the image from Windows, as described in
Chapter 1, Getting Started with the Raspberry Pi for Rasbpian.
The first boot
Insert your SD card, plug in a wired internet connection and an HDMI display, and
turn on the power. The first boot will take a few minutes with some screen flashing
and strange looking graphics or text. It will automatically reboot, and you will see
a screen with a language selection. If you don't have a keyboard hooked up, the
default (English) will get connected automatically; and then, you will see a screen
similar to this one:
On this screen, you will see the IP address assigned to the Raspberry Pi. You can
type the IP with the port 8080 address into your browser, and you will be presented
with a web GUI.
The default username is administrator and the password is [email protected]
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Windows IoT Core
Remote connections
You can connect to Windows IoT by either using PowerShell in Windows or SSH
connections, which will present you with a PowerShell command line running on
Windows IoT.
The easiest way is to connect using SSH with Putty or similar as you would normally
connect to any Linux-based machine.
To connect from Windows using PowerShell, perform the following:
1. Click on the Start menu and start typing powershell.
2. Right-click on Powershell and click on Run As Administrator.
3. Then, we need to type in a few commands in order to connect to IoT for the
first time:
net start WinRM
Set-Item WSMan:\localhost\Client\TrustedHosts -Value <IP Address>
After this, you will be able to connect from Windows PowerShell to IoT PowerShell
using the following command:
Enter-PSSession -ComputerName <IP> -Credential localhost\Administrator
The connection process may take up to 30 seconds.
When a connection is established, you will see the IP Address of
your device before the prompt.
Visual Studio (VS)
In this section, we will go through how to prepare Visual Studio 2015 for IoT, and we
will also take a look at the Hello World application to get familiar with the IDE.
Installing Visual Studio 2015
Use your favorite browser to search for Visual Studio 2015 Community edition,
which is completely free to use without any time limits; download and install it.
After installing VS start it up once and log in, if required, to the Live account you
used to download VS. Once it all seems loaded up we will need to shut it down
to install the IoT templates required to develop for the Raspberry Pi (or other
embedded devices running Win 10 IoT)
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Once again, use your favorite search engine and search for Windows IoT
Core Project Templates. You should use the official Microsoft http://www.
visualstudiogallery.msdn.microsoft.com/ link. There may be important
messages there, so read those. Click on the Download button and run the executable.
This will install additional Universal Windows Platform (UWP) templates that will
not only enable you to write background applications on unheaded Pis for Visual
Studio but also specific libraries that we will be using in universal apps.
Start Visual Studio up again, and find the new template under C#. Verify that the
template has installed correctly:
The Hello World application
This application will require you to have a monitor connected as we are first going
to create a Windows Universal Application. It also shows you how to prepare your
solution so that it can be used on the Raspberry Pi:
1. We will create a new project using this template; navigate to Templates |
Visual C# | Windows | Universal | Blank App (Universal).
2. Give it the name of HelloWorld and click on OK.
3. You may be prompted to Enable Developer Mode if you are using
Windows 10; navigate to Settings | Update And Security | For Developers.
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Windows IoT Core
4. The final step will be to add a reference to the IoT extensions required for the
Raspberry Pi specific features, such as GPIO.
5. Right-click on References | Add Reference | Universal Windows |
Extensions and check Windows IoT Extensions for the UWP.
Windows is designed using the XAML mark up. If you have ever worked with
Silverlight, then you should be familiar with XAML. XAML is a general purpose
object instantiation language, which is mostly declarative, such as HTML, but with
an XML twist. But no need to worry about the low-level mark up as Visual Studio
allows you to design visually!
There is also a dedicated software called Blend that is purely
used to create complex XAML layouts for applications that
may require them.
1. In the Solution Explorer snap in Windows, locate and double-click on
MainPage.xaml.
2. A new, blank designer view will open.
3. Select 40" IoT Device from the top because we will be making this view for
an IoT device with a large screen. There are options for smaller screens too if
you are using a mini LCD perhaps. This helps you lay out your design within
a perspective view. In advanced techniques, you can create separate views
for various devices using separate XAML files. These will all scale as best as
possible to the available screen.
4. You can now expand the Toolbox on the right-hand side and have a look
under XAML Controls.
5. From the Toolbox, click and drag button control onto the white designer
area. Then, drop it in TextBlock.
6. Resize the button control to be larger, as it may have dropped in at a really
small size.
7. While the button control is selected, change your Snap in view (in the right)
to Properties.
8. Find the Common tab and change the content value to change the text that is
displayed on the button; for example, Hello Word!
9. You can also change some properties for the text block, for example,
the font size.
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10. Then double-click on the button in the design view. This creates a code
snippet; change the view to the code area, and position your cursor on the
button click event code:
In the code, we will change the textBlock.Text value using this one line of code:
this.textBlock.Text = "Hello World!";
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Deploying the application
It is very simple to deploy the application to the Raspberry Pi, but first, we will
change the package name. Doing this is not that obvious unfortunately, but follow
these steps:
1. In the Solution Explorer Snap window, click on the Solution Explorer Snap
in tab.
2. Right-click on the HelloWorld project (not the Solution) and Properties.
3. Navigate to Package Manifest | Packaging.
4. The default value in the Package name is a Unique ID, and this is the name
of the process that will be created on IoT. For now, we can change this
to HelloWorld without spaces. When you want to publish an app to the
store, you will need to use NameSpace, for example, My.RaspberryPi.
HelloWorld.
5. Press Ctrl + S to save the solution, then close the window.
Now, to publish, we need to change a few settings and select the target device:
1. Change the x86 value in the top toolbar to ARM.
2. Next, to the green Play button, there is a small drop-down button; click on it
and select the Remote machine.
3. This will bring up a new window, which automatically discovers Windows
IoT devices running on your network. Make sure your Raspberry Pi is booted
into the Windows 10 Dashboard app.
4. Click on the device entry found under Auto Detected and then Select
(you will only need to do this once per session).
5. The project will build; if there are no errors, it will get published on the
Raspberry Pi and run your application. Visual Studio is not in Debug Mode!
6. On the Raspberry Pi, click on your button, and the text box will be updated
with the text you entered in the code earlier.
7. To stop debugging, click on the red Stop button.
You have now created your first Universal Application for the Raspberry Pi.
Debugging
One of the greatest features in Visual Studio is the debugging functionality. All these
features are already enabled on Windows 10 IoT installed on your Raspberry Pi, and
no extra configuration is required.
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After you click on Deploy (the green start button), Visual Studio automatically goes
into debug mode. In this mode, you cannot change any of the code; you can add or
remove breakpoints, view output in the debug console, and use various other debug
tools.
Visual Studio will also automatically break on unexpected errors and take you to the
code that caused this exception with details about the problem.
As a long-time C# developer, I can admit that these errors might
not make a lot of sense sometimes. The best thing is to search the
Web for part of the error message and see what other developers
have done to correct the problem. Stack Overflow usually provides
high-quality answers for many ambiguous error messages.
Breakpoints
While the application is in the code edit mode, look at the source code of the button
that we created earlier. You can add or remove breakpoints by clicking on the dark
grey bar at the left, which will highlight the line of code in red:
Click on Deploy and run. Your break point will be hit before when you click on the
button. To continue, click on the green Play button again, or F10 for step over, or F11
to step in (if it is a method you created or the source code is available)
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Unhandled exceptions
To experience this feature, we will create a deliberate unhandled exception.
It would be nice to demonstrate a Stack Overflow, but let's stick with a basic
arithmetic function:
1. Under your break point, add these lines of code, and do not add any
breakpoint to them:
int zero = 0;
this.textBlock.Text = (0 / zero).ToString();
2. Click on Deploy and run.
3. Click on the button on the IoT device and your first break point will become
a hit.
4. Press Continue to continue executing the code.
5. Straight after continuing that you should get an unhandled exception message:
DivideByZeroException was unhandled by user code
This is a simple, self-explanatory exception. If you ever run into deeper water, you
can use View Detail… under action to reveal some more debugging information.
These types of exception cause the application to crash whether you are in the Debug
or Release mode.
If you suspect that an operation may result in an unhandled exception, for example,
lots of arithmetic calculations, working with indexes, long running operations,
or external calls, you can wrap this code in try block, which will prevent your
application from crashing.
Amend the divide by the zero code as follows:
try
{
int zero = 0;
this.textBlock.Text = (0 / zero).ToString();
}
catch (Exception ex)
{
this.textBlock.Text = ex.ToString();
}
You can use the method to display error messages to the user or log exceptions to a
database.
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Samples
There is a large sample code package available to download from the code area.
These are official Microsoft Samples, and they demonstrate not only how to create
more advanced applications but also how to use the GPIO and other features on the
Raspberry Pi.
Windows 10 IoT WebGUI
You can access your Raspberry Pi via your browser. Simply enter the IP with port
8080 and use the default username and password provided earlier in this chapter.
As time goes on, this page will be updated to support more features and may even
completely change in the future. For now, we have access to various common
commands, such as Shutdown, reboot, processes, live performance graph, and
so on.
Setting up the startup app
The following are the steps to set up the startup app:
1. You can click on Apps on the left-hand side menu.
2. From the installed apps, find your app and click on it.
3. Once it is selected, click on Set Default.
4. You application will now start up after each boot:
5. Click on Reboot to test it.
WebGUI will still be available while your application runs.
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Peripherals
I tried to plug in various devices and see what happens with most of them not
doing anything. Popular ones seem to work, such as a USB mouse and keyboard
transceiver.
Just remember that power is still an issue on USB, so it may be a good idea to use a
powered hub.
You can find more information on supported devices by visiting: http://ms-iot.
github.io/content/en-US/win10/SupportedInterfaces.htm.
Bluetooth
Bluetooth is still a fairly new addition to Windows IoT as of writing this chapter. I
tried a generic Bluetooth dongle (unbranded), and it was installed successfully. It
found my TV and my Bluetooth keyboard while I was on WebGUI.
I was successful in pairing my keyboard and navigating the screen.
You may also succeed in paring Bluetooth serial port transceivers as it seems to be
supported on generic Bluetooth.
Wireless
Wireless support has been rapidly extended since the release candidate, and it
supports the official Raspberry Pi dongle and other popular chipsets used in many
other brands.
Summary
Even though Windows has various other ARM and MCU systems, Windows IoT
was developed from a blank canvas. With time, the support will continue to grow for
new devices and other ways to develop applications.
If you are interested in learning C# or are already a seasoned C# developer, this
finally looks like the light at the end of the tunnel for an alternative embedded OS,
other than the ever dominating *nix operating systems that were designed for these
sorts of devices years ago.
There are many advantages in using Visual Studio and the Universal App architecture,
but as of writing this chapter, there is still a lot of work to do for Microsoft.
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Running Your ownCloud
This chapter covers how to install the open source ownCloud on to the Raspberry Pi
2, which is a great, free, self-hosted alternative to services such as DropBox, Google
Drive, or Live Drive.
If you feel like you would like full control over the data, how you share it, and who
can access it, ownCloud is a great solution. It is a self-hosted file sync and share
server, which provides access through a web interface, the sync clients of WebDAV.
There are clients available for most operating systems, but even when you don't have
a client, you can always use a modern browser to get straight into your data.
Installation
As of this writing this chapter, ownCloud version 8 is the latest version available for
installation.
You may already have a few things that you require installed if have you followed
the previous chapters. In case you need a few extra packages, it is best to go through
the entire installation process from the beginning as described here.
Requirements
ownCloud requires a database storage engine, PHP, a web server, and data. As
usual, I recommend to use nginx as it is lightweight and powerful. You can learn
how to install nginx in Chapter 4, Using Fast Web Servers and Databases. It is also
recommended by the developers of ownCloud to use nginx as the web server.
To be able to access ownCloud from the World Wide Web (WWW), refer to the
dynamic DNS section in Chapter 2, Preparing a Network.
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MySQL
Update your repositories and install MySQL:
sudo apt-get update
sudo apt-get install mysql-server
During installation, you will be asked to set a root mysql password on a blue screen.
Use a strong password and save it into a program
such as Keepass so that you can quickly recover it for
the next time you need it.
After installation, we will enter into the MySQL database console and create a table
for ownCloud. You should replace the password in the script with your own strong
password:
mysql -u root –p
CREATE DATABASE owncloud;
CREATE USER [email protected] IDENTIFIED BY 'password';
GRANT ALL PRIVILEGES ON owncloud.* TO [email protected];
FLUSH PRIVILEGES;
exit
Remember the username, password, and table name if you have changed it, as it will
be required in the First Configuration section.
nginx and PHP
We will install a variety of packages for PHP followed by nginx as follows:
1. Run the following command:
sudo apt-get install php5-mysql openssl ssl-cert php5-cli php5common php5-cgi php-pear php-apc curl libapr1 libtool php5-curl
libcurl4-openssl-dev php-xml-parser php5-dev php5-gd memcached
php5-memcache
sudo apt-get install php5-fpm nginx
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2. After you have installed all the required packages, you can create a new web
folder, download the latest version of ownCloud, and unpack it to a new
folder called owncloud:
sudo mkdir -p /var/www/owncloud
cd /var/www
sudo wget https://download.owncloud.org/community/owncloud8.1.3.tar.bz2
sudo tar -xvf owncloud-8.1.3.tar.bz2
sudo chown -R www-data:www-data /var/www
3. We will generate a self-signed certificate, but you can get a free certificate
from https://letsencrypt.org. A self-signed certificate will show up an
error message on your browser, but all your traffic will still be encrypted
after you continue:
sudo mkdir -p /etc/nginx/ssl
sudo openssl req -x509 -nodes -days 36500 -newkey rsa:2048 -keyout
/etc/nginx/ssl/owncloud.key -out /etc/nginx/ssl/owncloud.crt
4. You will be asked to input various other information during the certificate
generation process. You can leave Country Name, State, Locality Name,
Organization, and so on, blank, but for Common Name, you must enter your
dynamic DNS address.
5. We will now create and edit the nginx configuration file at /etc/nginx/
sites-available/owncloud.
6. If you have decided to use a domain name for the WWW access, you will
need to adjust the server_name property accordingly. The DNS name and
the private IP of your Raspberry Pi is as follows:
server_name {domain.name.com},{pi's IP};
7. For simplicity, I only use my Pi's IP address and not DNS's IP address.
The first server block forces all non-SSL requests to be permanently redirected to the
SSL configured server block.
The SSL server block has quite a large configuration area. You can find the text
version in the code pack.
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If you have other sites running, you should pay attention to the root directive. If you
use /var/www/ as the root, you can then simply access the site by adding /owncloud
to your URL. If you would like to use your Raspberry Pi solely for ownCloud, you
can change the root to /var/www/owncloud/, and then you can access ownCloud
with your IP or DNS without adding a subfolder to your URL. I have left as
recommended for multi-tenant configuration where you are required to add /
owncloud to your URL. You may also choose to set up a subdomain locked to the /
owncloud directory, which is a good alternative solution. You should decide on this
once as changing it later may break ownCloud:
server {
listen 80;
server_name 192.168.1.21;
return 301 https://$server_name$request_uri;
}
# enforce https
server {
listen 443 ssl;
server_name 192.168.1.21;
access_log /var/log/nginx/sitename.access.log;
error_log /var/log/nginx/sitename.error.log;
ssl_certificate /etc/nginx/ssl/owncloud.crt;
ssl_certificate_key /etc/nginx/ssl/owncloud.key;
# Path to the root of your installation
root /var/www/;
client_max_body_size 10G; # set max upload size
fastcgi_buffers 64 4K;
# Some rewrite rules, more to come later
rewrite ^/owncloud/caldav((/|$).*)$ /owncloud/remote.php/caldav$1
last;
rewrite ^/owncloud/carddav((/|$).*)$ /owncloud/remote.php/carddav$1
last;
rewrite ^/owncloud/webdav((/|$).*)$ /owncloud/remote.php/webdav$1
last;
# Protecting sensitive files from the evil outside world
location ~ ^/owncloud/(data|config|\.ht|db_structure.xml|README) {
deny all;
}
# Configure the root location with proper rewrite rules
location /owncloud/ {
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rewrite ^/owncloud/.well-known/host-meta /public.
php?service=host-meta last;
rewrite ^/owncloud/.well-known/host-meta.json /public.
php?service=host-meta-json last;
rewrite ^/owncloud/.well-known/carddav /remote.php/carddav/
redirect;
rewrite ^/owncloud/.well-known/caldav /remote.php/caldav/
redirect;
rewrite ^/owncloud/apps/calendar/caldav.php /remote.php/
caldav/ last;
rewrite ^/owncloud/apps/contacts/carddav.php /remote.php/
carddav/ last;
rewrite ^/owncloud/apps/([^/]*)/(.*\.(css|php))$ /index.
php?app=$1&getfile=$2 last;
rewrite ^(/owncloud/core/doc[^\/]+/)$ $1/index.html;
try_files $uri $uri/ index.php;
}
location ~ \.php(?:$|/) {
fastcgi_split_path_info ^(.+\.php)(/.+)$;
include fastcgi_params;
fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
fastcgi_param PATH_INFO $fastcgi_path_info;
fastcgi_param HTTPS on;
fastcgi_pass unix:/var/run/php5-fpm.sock;
}
# Optional: set long EXPIRES header on static assets
location ~* \.(?:jpg|jpeg|gif|bmp|ico|png|css|js|swf)$ {
expires 30d;
# Optional: Don't log access to assets
access_log off;
}
}
Now you have enable ownCloud and disabled the default configuration if you just
installed nginx:
sudo ln -s /etc/nginx/sites-available/owncloud /etc/nginx/sites-enabled/
owncloud
sudo unlink /etc/nginx/sites-enabled/default
Finally, we need to restart everything for the new configuration to take effect:
sudo service nginx restart
sudo service php5-fpm restart
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Running Your ownCloud
Permissions
ownCloud will store all your files as normal files in a directory. It uses the database
to index files to improve querying speeds. If, for whatever reason, your ownCloud
stops functioning properly, you can still access all the files directly without any
complicated recovery procedures.
ownCloud runs under www-data. To fix file permission issues, the easiest solution
is to add www-data to the pi group, and then create a subfolder with the www-data
owner applied to it:
sudo usermod -a -G pi www-data
The following two commands require you to add your directory destination
depending on how and where you have mounted your file system. We will create a
new subdirectory and assign the ownership to www-data. We also need to create a
temporary directory for uploaded files:
sudo mkdir -p /mnt/{your mount point}/owncloud
sudo chown -R www-data:www-data /mnt/{your mount point}/owncloud
sudo mkdir -p /mnt/{your mount point}/owncloud/tmp
sudo chown -R www-data:www-data /mnt/{your mount point}/owncloud/tmp
The first configuration
By this point, everything has been preconfigured for the ownCloud application. The
final step, which is only required once, is to run through a step-by-step configuration
wizard using your browser:
1. Open your browser and type in the IP address or DNS name of your
Raspberry Pi.
2. You will see a certificate error. Depending on the browser you use, you may
add this certificate to trusted, or click on the button to continue:
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Chapter 11
3. If everything went as planned, you will see the initial configuration screen of
ownCloud.
4. Type in an Admin username and password (use a strong password as we
should not be using this account often). This is the user that will be able to
create new users, change configuration, and so on. After creating an admin,
we will create a normal user that you should use from here on.
5. The next input asks you about your data folder. This is where you input the
directory that we created earlier and set the permission on.
6. In the last step, we need to input the database settings with the username,
password, and database that we created earlier. The user name is owncloud
(not [email protected]), followed by the password you entered, and the
table name of owncloud. Leave the localhost as it is.
7. Finally, we can click on Finish Setup. Then, ownCloud will configure the
database and test for any issues that may need to be resolved.
After several seconds, you will see the main dashboard presented with a welcome to
the ownCloud page, offering several apps to be downloaded and ways to connect to
ownCloud.
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Running Your ownCloud
The admin configuration
If you have just logged in as the admin to the dashboard, it is highly recommended
to create a user that you will be using for your daily cloud tasks:
1. In the top-right corner, you will see your admin username and a drop-down
menu. Click on it, and then click on Users.
2. Before creating a user on this page, click on groups and click on + Add
Group to create a new user group, for example, users.
3. Now, you can simply type in your username and password; make sure the
new group is ticked, and click on Create:
By creating a new group, you can now better manage restrictions or options that you
would like to use for anybody under this or other new groups later on.
For example, on this page, you can set quotas for each group.
The server admin
While still logged in as admin, click on the admin user name in the top-right corner,
and then click on Admin. You will land on the sharing options page by default.
On this page, you may notice a few security and set up warnings. If you see anything
critical, you can endeavor to resolve the issues by reading the documentation online.
As a standard, there is nothing critical that needs to be changed here, but reading
through the available options, you may spot something you like or dislike and adjust
it accordingly.
The first option that allows you to tune for groups is Restrict users to only share
with users in their groups.
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Chapter 11
When an update is released, you will revisit this page to enable the update mode,
and create configuration backups.
You can jump to various sections of the page using the menu on the left.
Installing apps
While logged in as admin via the WebGUI, you can click on the top-left link, which
is next to the ownCloud icon. A drop-down menu will appear, and you will see a
button to add apps:
The free edition comes with basic file support and some nice extras. The Enterprise
edition comes with official support for Calendar, contact management, and
synchronization.
On this page, you will see a list-enabled official apps, such as the picture or PDF
viewers. There a few more apps that are disabled; to view them click on the Not
Enabled menu item on the right-hand side.
No need to worry about the lack of apps though, as ownCloud was designed to be
extensible. There is a massive collection of user made apps that you can install for
free from https://apps.owncloud.com.
On the apps page, click on the cog icon in the bottom-left corner, and enable
Experimental Apps to allow third-party apps to be installed.
If you experience any problems with viewing or starting downloaded apps, you may
need to set the www-data owner on the folders that you will be creating.
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Running Your ownCloud
Calendar
To enable calendar functionality on ownCloud, we will install a highly rated app
called Calendar Plus:
1. On the https://apps.owncloud.com site, search for this app and
download it.
2. Extract the zip file into a directory called calendar plus.
3. To install the app, we need to upload the unzipped directory into the
/apps directory located at /var/www/owncloud/apps. Use Filezilla to
connect to your Raspberry Pi over SFTP, and upload the directory into the
apps directory.
4. In the WebGUI on the Apps page, click on Not Enabled and find Calendar+
at the bottom of the page. Click on Enable:
Other apps
The https://apps.owncloud.com website has an incredible collection of various
apps available, and you can install all of them in the same way unless the author
provides extra steps in the description of the app.
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Chapter 11
Daily functionality
If you have checked out the configuration pages, you can log out as admin and log in
as the user you have created for yourself using the Web GUI.
For computers and devices running on your local network, you can install the
client applications to your desktop or mobile computer and use your internal IP
or Pi's DNS.
The World Wide Access
If you have decided to use ownCloud on WWW using a dynamic DNS service, the
first thing is to check whether it is configured properly. An easy way to do this is to
download the client application onto your smart phone or 3G-enabled tablet.
Install the application, and then switch off Wi-Fi to get on to a mobile network, such
as 3G. Not all routers support the loopback DNS lookup, which means that trying to
access your IP from your IP may fail, but using an external network will verify that
your ports have been forwarded properly.
Start the application and enter your details on the login screen. The client application
will do a quick connectivity test and inform you about the state.
If you have logged in, you can try and turn your Wi-Fi back on and see if the client
will carry on as normal.
Summary
The Raspberry Pi 2 can now be your solution to going independent on cloud storage.
As long as you have some redundancy setup on your storage media, you will be able
to mostly disconnect from the big corporate giants and gain full control over your
data again.
In the next chapter, we will look at using some of the server-side applications, such
as databases and nginx, to work with storing GPIO data to monitor the weather.
[ 131 ]
The Internet of Things –
Sensors in the Cloud
Now that you have learned the essentials of running software applications on your
Raspberry Pi 2, it is time to apply your newly acquired knowledge. This chapter will
be about Operating System and agnostic language programming.
Your mission, if you wish to accept it, is to find your favorite flavor of Operating
System and programming language while I help you build a foundation on the
electrical prototyping.
In this chapter, we will focus on the following topics:
• Understanding power requirements and selecting correct cables
• Working with transistors
• Getting to know Integrated Circuits (IC) and their purpose
• Windows IoT, events, and real-time systems
• Working with the Cloud for the IoT integration
These topics will expand your basic electronics knowledge and show your good
prototyping practices that can be used on any embedded platform, such as your
Raspberry Pi 2.
Ultimate decisions on the software completely depend on your own personal
preferences. By doing this, you will gain confidence in problem solving and
appreciate the vast amount of tools and resources available on the Internet.
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The Internet of Things – Sensors in the Cloud
If you ever get stuck on a software problem, the best solution is to take a
90-minute break away from your computer, or go to bed and come back
to it the next day. If it seems like you are stuck on a particular software
problem for days, consider asking your question differently. Do not get
hung up on one particular way, as your problem has, most probably,
already been solved, and there is already a great solution to it out there.
What is IoT?
The Internet of Things are things with sensors that are embedded with electronics
and software. The things are connected to a network, most likely the Internet.
The Internet of Things started with machine-to-machine devices, such as alarm
systems or GPS trackers, and slowly expanded to home convenience gadgets,
such as power grid monitoring tools or some form of home automation.
"Experts estimate that the IoT will consist of almost 50 billion objects by 2020."
– Wikipedia
To build a successful IoT device, you will need to learn about software, the essentials
of which are covered in this book. You also need to learn about electronics, which
will also be covered in this chapter.
Ohm's law
Ohm's law is a fundamental concept to try and understand before you venture
into the prototyping world. One of the main reasons Ohm's law is so widely
misunderstood is because it has various equations that originate from a single,
mathematical equation.
You can find more information about this diagram and Ohm's law in Chapter 9,
Running Your Pi from a Battery's Power Source. I have included this diagram here for
quick reference as I will demonstrate how to use some of the provided equations:
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Chapter 12
How much power?
In Ohm's law, power (W) is know as watts. Understanding how to calculate watts is
pretty much the most important question that you should be able to answer easily.
For example, what size cable do I need?
• Cables are rated at how many amps they can carry. If you know how many
amps you require, then you know which cable to use.
If you select an incorrect cable size, this usually results in
electrical fires, as friction will heat these cables up until they
melt and eventually ignite.
To work out how many watts (W) a device uses, you will typically multiply volts (E)
by amps (I).
Watts = Volts x Amps (W = EI)
• 5 volts x 1 amp = 5 watts (such as the Raspberry Pi)
• If you have a device that requires 60 watts and is rated for 240 volts, then you
can work out these amps by dividing watts by volts.
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The Internet of Things – Sensors in the Cloud
Amps = Watts / Volts (I = W/E)
• 60 watts / 240 volts = 0.25 amps (this is a light bulb)
• Once you know how many amps you need to transfer, you can use an
American Wire Gauge (AWG) table to check the size of cable that you will
require over the distance needed:
It is always recommended to go a size lower (thicker cable) if
you are close to the limit of the cable. This is generally within
10% of the capacity.
Here is an illustration of the how the AWG size works and a conversion to metric
millimeters for radius and millimeters squared for the area:
[ 136 ]
Chapter 12
Higher voltage is your friend over longer distances. Generally, the higher the
voltage, the thinner the cable you need to use to supply the same amount of amps,
reducing the cost of the cable.
In most cases, the highest voltage that we can use is what is
supplied to our home grid 110v/220v, and this will still be
the most efficient way to transport power for distances up
to 300 feet (100 meters).
You will find this useful in many projects that you are ready to put into production
away from your prototyping bench. For example, to power remote devices, such as a
weather station that controls an irrigation system 120 meters away from the nearest
socket, but it may as well be something in your loft, connected within one box:
• Raspberry Pi 2: 5 volts 1 amp
• USB GPRS Modem: 5 volts 0.8 amp
• Medium water pump: 24 volts 2.5 amp
• 6 x Solenoids: 9 volts 1 amp
• Relay board: 12 volts 0.5 amp
You will learn how to apply Ohm's law and use IC to deal with this problem
efficiently later in this chapter.
Choosing sensors
The answer to this question depends on what you want to build. Sensors come as a
variety of packages, operated by various voltages, and interfaced with some kind of
communication standard.
Resistors, fuses, and diodes
These are typically the easiest elements of electrical design to understand. If you are
planning to create a device, you should find a basic electronics course to gain good
understanding of these basics before continuing.
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The Internet of Things – Sensors in the Cloud
Transistors
Everybody that uses a computer will have probably heard of a transistor. What is a
transistor really? It is a semiconductor device that can be used to amplify or switch
electronic signals and electrical power. A semiconductor is a solid substance that can
conduct electricity when a certain condition has been met; otherwise they act as an
insulator.
Their packages are easily identified as they usually consist of three wires (legs).
These legs are named Base (b), Collector (c), and Emitter (e):
The preceding illustration shows various packages that a transistor can be found in.
The ones that look like they have two legs, actually have their base on the other side.
The illustration also shows two different types of transistors: NPN and PNP. They
essentially do the same thing, but NPN transistors are used to switch higher voltages
and PNP lower voltage than what's used in your main circuit. Also, PNP transistors
are turned on when pulling the base low while NPN is turned on when you provide a
voltage to the base.
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Chapter 12
Usually, in prototyping, we are mostly interested in switching higher voltages, and
from here on, we will be working with NPN transistors.
It may sound confusing at first, but just think of a transistor as a plain old switch.
When you apply the correct amount of current to an NPN transistor's base, it is like
your finger pushing a button. Once you get to the correct pressure, the switch will
turn on, and the current will flow through the collector to the emitter. The amount of
power (A) used to trigger a transistor is typically very low and sage for the GPIO's
on the Raspberry Pi.
Looking at the sample circuit (bottom right) in the illustration, you can see a 9v
power source connected to a resistor, LED, and then to the collector of the transistor.
The emitter is connected to GND. This is pretty much how you will wire a switch. In
the digital world, to turn on this switch, we need an extra input—base. For example,
we will use GPIO PIN 4. This can be an output from any kind of embedded device
with a 3.3v, 5.0v, or a higher voltage. The maximum voltage depends on the resistor's
technical specification.
The 10k resistor can be of any value between 1K and 20K, and it should always be
connected before the base of the transistor. The resistor is there to limit the maximum
current that flows through the base of the transistor, preventing damage to the
transistor.
Once the I/O is set high in software, the switch will close and the LED will illuminate.
You just learned the basics of transistors. As you build more
designs, you will find new circuits that require a combination of
transistors to achieve a specific goal.
Using transistors in such a way makes switching other voltages much easier from an
embedded platform, using a low amount of current.
You should always try and find the transistor marking, and you should search for
its datasheet to understand the minimum and maximum values it can handle. The
datasheet will also provide the minimum current required on the base to turn it on.
Transistors are typically used in low-voltage designs. To turn on high voltage, such
as 220 volts, you should almost always use a relay. Yes, you can use the transistor to
turn the relay on.
[ 139 ]
The Internet of Things – Sensors in the Cloud
Integrated Circuit Packages
These are a variety of other IC packages that you will find. You should be able to use
any of these with nothing more than a soldering iron or breadboard.
Other packages such as QFN require specialist equipment to be
prototyped with. An example of such a package is BCM2836,
and it can be found on your Raspberry Pi 2.
[ 140 ]
Chapter 12
Putting it all together
This circuit demonstrates switching a high-voltage 48 volt DC motor.
Be very careful when working with high voltages. Incorrect wiring
will cause irreparable damage. Switching mains voltages may be
lethal, and please do not attempt this if you are in doubt.
Accurate data using Arduino
The Raspberry Pi typically runs on event-driven Operating Systems. This mean that
a queue of events gets processed by the processor as fast as the processor can handle
it. Unfortunately, even if your processor is idle, there is still an overhead in the event
system that causes significant problems with real-time sensors or applications.
There are real-time Operating Systems for the Raspberry Pi, but this will severely
limit the capabilities that you have learned to use and love. Real-time Operating
systems guarantee that an action, such as some code, will be completed in the
predefined time. A very popular Operating System for these types of simple yet
extremely accurate tasks is the Arduino family IC. They are amongst the best for
doing millions of tasks over and in a very precise time.
We will look at some examples of how an Arduino IC will help you gather data by
showing a use case of building a weather station.
[ 141 ]
The Internet of Things – Sensors in the Cloud
Building a weather station
A great project to work on is building a weather station. The Raspberry Pi 2 has so
much processing power to offer:
• It can store a large amount of data in a database with ease
• It can be its own web server running with a variety of programming
languages
• It can crunch numbers, create statistics, and eventually become nice graphs
• It can even stream live videos using WebRTC or RTSP
Real-time embedded devices
Atmel AVR (used on Arduino) and PICAXE are very well-known microcontrollers
that run code with real-time precision. The advantage of these microcontrollers is
that you can program them with simple code once, upload the code, disconnect them
from the development board, and use them like a standalone IC.
Your initial cost for a development board maybe about the same as a Raspberry Pi on
its own, but after this, getting the programmable Microcontroller Unit (MCU) will
cost a few dollars, and will be even cheaper for tiny versions.
There are expansion boards available for some of these embedded devices, mostly
for Arduino.
The data communication
Real-time devices also offer very precise or faster data communication between
various other devices by not only offering hardware interfaces but also software
bit banging.
Bit banging is a technique for any kind of serial communication
using software instead of some dedicated hardware.
Real-time events
The essential benefit of an MCUs is that you would require it when building a
weather station is required when counting time sensitive actions, such as wind
speed, which must be calculated every second without any delay.
You write a small function of code that executes when a selected pin is triggered.
This is known as an interrupt. This code is as simple as incrementing a counter.
[ 142 ]
Chapter 12
The main program is an endless loop of code or an internal-timed interrupt. Not all
MCUs offer internal-timed interrupts, but what is critical is that it always runs at
a selected time, for example, every 60 seconds. On an MCU, this is guaranteed to
run every 60 seconds to the microsecond. This is crucial to make sure that you can
run an algorithmic function, which uses your wind counter to save the wind speed.
On an event driven OS, you may get highly inaccurate readings caused by delayed
processor queues or the optimized execution.
Analog inputs
The Raspberry Pi lacks analog inputs. MCUs usually have more analog inputs than
digital ones. On tiny versions, they may even completely lack digital inputs.
Analog inputs will be very useful to read the direction of the wind, as wind vanes
usually output a calculated subvoltage from the input voltage to inform you of the
direction. Something like a potentiometer, but more simply, it is like various resistors
connected to a reed switch, which will activate a given circuit.
There are still a lot of other applications that can be useful for analog inputs.
Parts required
The most affordable and pretty complete package is offered by Sparkfun—a wind
vane, anemometer, and rain counter, with cables and a complete installation mount.
Adding extras to this, such as instruments to measure UV light, atmospheric
pressure, and temperature, is a breeze.
You will also need a Raspberry Pi and a programmed Arduino MCU or similar.
Storing data on the Cloud
At some point of any project, you will, most certainly, want to store collected
data somewhere. Usually, this is from collecting sensors, but it could also be
debugging data.
The Cloud is a network of servers that can provision virtual machines for any use.
Usually, you start from one server, but you always have the ability to increase the size
or bundle several virtual machines to act as one endpoint. All this is usually handled
by a nice frontend, such as Azure, Amazon AWS, or the Google Cloud platform.
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The Internet of Things – Sensors in the Cloud
Phant
Phant is a logging tool developed by Sparkfun Electronics and is ready to be used
free of charge at https://data.sparkfun.com; it stores data in JSON format. JSON
is easy to read and compress, but most importantly, it's dynamic; dynamic meaning
that you don't build relationships between each data packet, as in traditional SQL
servers. This means that each data packet can contain any variety of structures that
you save to Phant.
You can find yourself a very cheap Linux-based virtual machine and install your
own Phant platform to take full control of your cloud data. This is an extremely easy
way to allow you access to shared data anywhere in the world, as long as you have
an Internet connection.
Summary
In this chapter, you learned the basics of electrical engineering and the external
system's integration. The possibilities are endless and only confined to your own
imagination. In case you ever seem to get stuck, it is worth visiting some of these
great sites for more information.
For Stack Exchange, use the following:
• Electrical Engineering: http://electronics.stackexchange.com/
• Raspberry Pi: http://raspberrypi.stackexchange.com/
• Stack Overflow (Programming): http://stackoverflow.com/
• Ask Ubuntu (Linux related): http://askubuntu.com/
For other sites, use the following:
• Arduino Forums: https://forum.arduino.cc/
• PICAXE Forums: http://www.picaxeforum.co.uk/
• Searching the internet
Thank you for your interest in this book, and I wish you happy prototyping!
[ 144 ]
Index
Symbols
.NET
about 48
and ASP.MVC 48
DNX, installing 50
MVC 52
MVC Website, running 50, 51
nginx 52
other .NET applications 52
prerequisites 49
A
adapters
URL 17
admin configuration
about 128
apps, installing 129
Calendar Plus 130
other apps 130
server admin 128
AJAX GET Request
URL 48
Alamode 6
alsamixer
using 96
Apache
versus Kestrel 39
versus nginx 39
Aplay
for audio playback 95
Apple Filing Protocol (AFP)
about 67
Netatalk, configuring 67
Netatalk, installing 67
shares and time machine 68
Arduino
Forums, URL 144
used, for data accuracy 141
Ask Ubuntu (Linux related)
URL 144
ASP.MVC 48
audio, playing
about 95
AirPlayer, using 96
alsamixer, using 96
Aplay, for audio playback 95
OMXPlayer, for audio playback 95
audio recording 6
B
battery power source
about 101
capacity 107, 108
hardware requirements 101, 102
implementing 107
BitTorrent Sync
about 68
BTSync 2, installing 68-70
boot process 10
Broadcom chip 35
BTSync 2
installing 68-70
C
CAN bus 7
Cloud
data, storing on 143
Phant 144
Crystal Disk Mark 12
[ 145 ]
D
F
daily functionality
about 131
World Wide Access 131
data
accuracy, Arduino used 141
database, installing
MySQL, installing 54
phpMyAdmin, installing 55, 56
SQLite, installing 56, 57
decoders
enabling 35
licenses, buying 35
distribution
updating 32
Dot Net Execution Environment (DNX)
about 49
installing 50
Dot Net Package Updater (DNU)
about 49
installing 50
Dot Net Version Manager (DNVM)
about 49
installing 50
drive, formatting
disk, remounting after reboot 63
drives, mounting 62
EXT4 partition, creating 62
drivers
listing 60
Dynamic DNS
about 28
client, installing 28, 29
free network 29
FastCGI 53
files, accessing
about 63
FTP service 63
File Transfer Protocol (FTP) service
about 63
FileZilla, connecting with 64
WinSCP, connecting with 64, 65
FileZilla
connecting with 64
Fingerprint scanners 8
firmware
updating 32
Freeciv
about 76
configuring 76
installing 76
playing 77
E
Electrical Engineering
URL 144
eth0 port 16
Ext4
about 61
partition, creating 62
external storage
connecting 59
G
games servers 74
H
hardware, limitations
about 11
network speeds 11
time 12
USB bottlenecks 11
hardware RAID
about 70
configuring 70
massive storage 71
redundant storage 72
hardware requirements, battery power
source
battery packs 103
charging station 102
voltage regulator 104, 105
hardware watchdog
about 33
enabling 34
testing 35
HDMIPi 94
[ 146 ]
HDMI to VGA converter 6
home automation 7
HTTP streaming
about 84, 85
object detection and tracking 88
overlay watermark, removing 88
text overlay 87
web conferencing 85, 86
X desktop, streaming 86
HUD sample
about 88
inline variables 89, 90
overlay binary, using 89
overlay code, compiling 90
L
I
M
inline variables 90
Internet 3G dongles 5
internet configurations
about 26
business packages 27
home packages 27
Internet of Things (IoT)
about 110, 134
first boot 111
Python, for Linux 110
Python, for Windows 7 and 8 110, 111
remote connections 112
requisites 110
URL 110
iPerf 25
Macintosh
Apple Filing Protocol (AFP) for 67
media add-ons
Alamode 6
HDMI to VGA 6
IR receivers 6
Multicard readers 6
TV and radio receivers 6
Webcams 6
Micro Controller Unit (MCUs) 142
Minecraft
about 78
configuring 79
installing 79
playing 80
MPEG-2 36
MVC
and nginx 52
MySQL
installing 54, 55
J
Java Hard-Float
installing 78
JavaScript web programming language 45
Jessie
updating to 73
K
Kestrel
versus Apache 39
versus nginx 39
licenses
URL 35
Local Area Network (LAN)
about 15, 16
Bcast 16
eth0 port 16
HWaddr 16
inet6 addr 16
inet addr 16
loopback (LO) interface 17
Mask 16
wlan0 interface 17
N
Netatalk
configuring 67
installing 67
network
bandwidth, recommended 25
basic tests 23, 24
benchmarking 23
benchmarking tools 24
[ 147 ]
iPerf 25
speedtest application 24
testing 23
Network Attached Storage (NAS) 4, 62
nginx
extra frameworks 43
installing 40, 41
versus Apache 39
versus Kestrel 39
virtual hosts, configuring 41, 42
Node.js
about 45
installing 45
Node Package Manager (NPM)
about 46
Node.js server 46, 47
URL 46
NO-IP domain
URL 29
NOOBS
URL 9
O
Ohms law
about 134
power (W) 135-137
OMXPlayer
for audio playback 95
for video playback 95
OpenArena
about 77
configuring 77
installing 77
playing 78
OpenTTD
about 74
configuring 75
installing 75
lan_internet 75
playing 75
server_advertise 75
server_bind_ip 75
server_name 75
server_port 75
OSMC
about 96
add-ons, using 98
AirPlay 98
CEC, enabling 99
configuring 97
installing 96
media sources 98
other codecs, enabling 97
overclocking 99
performance optimization 99
remotes, enabling 99
wireless configuration 97
overlay binary
URL 88
using 89
overlay watermark
removing 88
ownCloud
about 121
admin configuration 128
first configuration 126, 127
MySQL 122
nginx and PHP 122-125
permissions 126
requisites 121
URL 129, 130
P
packages
updating 32
peripherals
about 4, 120
Bluetooth 120
CAN bus 7
fingerprint scanners 8
home automation 7
Internet 3G dongles 5
Joysticks 7
keyboards and mice 5
URL 5, 120
USB hubs 5
USB missile launcher 7
USB to SATA 7
weather station 8
wireless 120
Wireless USB network adapters 5
Phant 144
[ 148 ]
PHP
installing 53
phpMyAdmin
installing 55, 56
PICAXE Forums
URL 144
pi.kula.solutions 28
power (W) 135-137
Python
for Linux 110
for Windows 7 110
for Windows 8 110
URL 45
Python API
about 43
executing 43, 44
R
Raspberry Pi
boot process 10
design 9
hardware, limitations 11
other capabilities 10
Raspbian, installing 8, 9
updating 31
URL 69, 144
Raspberry Pi 2
hardware requisites 1, 2
power supply 2, 3
SD cards 4
USB hub 3
Raspbian
installing, on Raspberry Pi 8
S
Samba
about 65
configuring 65, 66
installing 65, 66
network shares 66, 67
SD cards 4
SD Formatter
URL 8
selective settings 73, 74
self-signed certificate
URL 123
sensors
diodes 137
fuses 137
merging 141
resistors 137
selecting 137
transistors 138-140
shairport 96
slideshows
about 93
fbi, using 94
videos, playing 94
Sparkfun Electronics
URL 144
speedtest application 24
SQLite
installing 56, 57
Stack Exchange 144
Stack Overflow (Programming)
URL 144
static network address 22
storage
medium, preparing 60
T
Text Overlay 87
U
Universal App Platform (UAP) 109
updation, Raspberry Pi
distribution, updating 32
firmware, updating 32
outcomes 33
packages, updating 32
USB bottlenecks 11
USB hubs 3-5
USB missile launcher 7
USB to SATA controller 7
UV4L
installing 81, 82
URL 81
UV4L-RaspiCAM, configuring 82, 83
Web Real-Time Communication (WebRTC),
installing 83
WebRTC streaming 83, 84
[ 149 ]
V
VC-1 36
virtual directory
URL 44
VisualGDB
about 91
URL 91
Visual Studio
about 112
application, deploying 116
debugging 116
debugging, breakpoints 117
debugging, unhandled exceptions 118
Hello World application 113-115
samples 119
Visual Studio 2015, installing 112, 113
voltage regulator
about 104
discharge characteristics 107
discharge curves 106
Ohms law 104-106
Windows 10 IoT WebGUI
about 119
startup app, setting 119
WinSCP
connecting with 64
URL 64, 65
Wireless configuration (Wi-Fi)
about 17
console, setting up from 18-21
desktop, setting up from 18
wicd-curses, using 21, 22
wireless adapters 17, 18
Wireless USB network adapters 5
wlan0 interface 17
World Wide Access (WWW) 131
World Wide Web (WWW) 121
X
xboxdrv 7
X desktop
streaming 86
W
weather station
about 8
analog inputs 143
building 142
data communication 142
parts 143
real-time embedded devices 142
real-time events 142, 143
web conferencing 85, 86
WebRTC
about 83
streaming 83, 84
[ 150 ]
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