Workshops presentation and lab notes
mbed
Hello World
1
Agenda
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Introduction to mbed
Lab 1: mbed registration and Hello World demo
Lab 2: Other IO
Lab 3: Interfacing with sensors
Lab 4: Output devices, a TextLCD
Lab 5: Rapid prototyping, Build a datalogger
Lab 6: Rapid Prototyping: Offline debug with CMSIS-DAP
mbed
Hello World!
Introduction to mbed
3
What’s happening in Microcontrollers?
• Microcontrollers are getting cheap
– 32-bit ARM Cortex-M0+ Microcontrollers < $0.50
• Microcontrollers are getting powerful
– Lots of processing, memory, I/O in one package
• Microcontrollers are getting interactive
– Internet connectivity, new sensors and actuators
• Creates new opportunities for microcontrollers
Opportunities for Microcontrollers
• Before the 1980’s computers were used and applied by
computer scientists
• Now democratised for everyone to use
– Office, home, entertainment, leisure
• Microcontroller technology is currently applied by
professional embedded developers
• Microcontrollers interact with “the real world”
– Sensors, actuators and communication, define their application
– Their potential is greater than the home computer
Barriers for Microcontrollers
• What prevents microcontrollers from being designed in?
• Conceptually simple things can be hard to prototype
– I want to send an SMS when my cat comes through the cat flap
• Repetition of choices to make:
– Microcontroller, Tool chain
– Dev board, Sensors
– It’s not difficult, but can be tedious and time consuming
• Overhead for starting a new project
– Fine for a long complex projects
– A deterrent for quick experiments and tests
Rapid Prototyping
• Rapid Prototyping helps industries create new products
– Control, communication and interaction increasingly define products
– Development cycles for microelectronics have not kept pace
3D Moulding
3D Printing
2D/3D Design
Web Frameworks
mbed.org - Rapid Prototyping for
MCUs
• Fastest way to get started with ARM microcontrollers
– Plug ‘n’ Play Hardware, Online Compiler
– Get setup and run “Hello World!” very quickly
– Removes entry barriers to MCU technology
• Focused on rapid prototyping for a diverse audience
– DIP form-factor, High-level APIs, Developer website
– Technology and tradeoffs to enable fast experiments
– Platform approach for developer ecosystem
• Launched at ESC Boston with live demo
– Internet-enabled “Twittering Billy” read out tweets
– An embedded internet device, prototyped in ½ day
– Over ¼ million video views in first week!
mbed Approach
• Focus on tools supporting the earliest stage of design
– Point of entry and Getting Started
– Experimentation and Rapid Prototyping
– Apply technology and trade-offs that support this goal
Proof of Concept
Specification
Implementation
• Provide a platform that can built upon
– HDK is a “recipe” enabling mbed features in 3rd party designs
– SDK enables reuse and portability in the developer ecosystem
mbed SDK
• C/C++ SDK for ARM Microcontrollers
– High-level APIs and standard environment
– Low level control as needed
– Portable across different ARM silicon vendor MCUs
• Built on industry standard technology
– ANSI/ISO C/C++
– CMSIS Compliant
– Compatible with all major professional MCU tools
• Open Source
– Released under permissive Apache 2.0 license
– Suitable for commercial and non-commercial use
– Managed, maintained and tested by ARM
mbed HDK
• HDK for ARM Microcontroller Boards
– MCU sub-system and debug interface architecture
– Includes on-board USB interface with 3 endpoints:
• Drag-and-drop FLASH programmer, Virtual Serial Port, Debug
– Enables standard connection on low-cost boards, starter kits, modules
• Built on industry standard technology
– USB Device
– CMSIS-DAP Debug Interface Protocol
– Compatible with Windows, Mac, Linux
• Free for commercial and non-commercial use
– Portable across different ARM silicon vendor MCUs
– Developed, tested and maintained by ARM
mbed HDK On-board Interface
• On-board USB interface for low-cost development boards
– Supports driverless MSD Programming and CMSIS-DAP Debug
– Interface implemented as firmware on selected Cortex-M MCUs
mbed-enabled Development Board
Composite USB Device
SWD
FLASH Programmer (MSD)
CMSIS-DAP Debug (HID)
Virtual Serial Port (CDC)
USB
mbed Interface
(USB Cortex-M MCU)
Reset
Target MCU
(Cortex-M MCU)
UART
Enables simple USB drag-n-drop reprogramming of demo code
through to full debug connection to ARM toolchains
mbed-enabled Hardware
• Expanding range of off-the-shelf mbed-enabled hardware
– ARM Cortex-M0, M0+, M3 all represented; M4 TBA
– DIP prototyping modules, Arduino eval board form-factors
– Available through worldwide distribution
TBA...
$49
$45
• Design and production
$13
$20
– All boards implement the mbed HDK
– Hardware is designed and/or made by ARM or 3rd parties
– mbed HDK enables anyone to build alternate board designs
Current message: mbed.org/explore
mbed
Hello World
Lab 1
mbed registration and hello world!
15
Registration
• For these lab sessions, we are
using :
– mbed LPC1768
– mbed Application board
• mbed microcontrollers enumerate
as a Mass Storage Device (USB
disk)
• Double-click the mbed.htm file on
the mbed USB disk
• Log in or sign up for a new account
Getting Started
• Useful resources linked
from the first page,
including very clear links
to “Hello World” and the
Getting Started guide
• Compiler linked from
front page
Getting Started
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Create or open a project in the Program Workspace
Develop code in the text editor
Save and compile
Compiler outputs
– Errors and warnings
– -or– A downloadable binary
• Save to the USB flash disk
Getting Started
• Once the file has saved to the flash disk, it needs to be
programmed into the microcontroller
• Press the button on the mbed module
• Your code will start running!
mbed
Hello World
Lab 2
Rapid Prototyping:
Other IO
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mbed Application board
http://mbed.org/cookbook/mbed-application-board
DigitalOut and Analog Input
• In the hello world session, we simply compiled the default
program – blinky, but we didnt take too much notice of the
code
• It was simple, it set up a digital output (DigitalOut) called
“myled” and run a loop forever turning it on and off.
• Lets see if we can begin to influence this.
What IO is there?
• Take another look at your compiler window. In your default
project there the mbed library with a “+” box. Try expanding
this, and exploring the libraries.
• Note that these are libraries that relate to the microcontroller
on chip hardware.
• We’ll be using the AnalogIn object, so take time to have a look
at it’s API
DigitalOut and Analog Input
• The AnalogIn object returns a normalised float between 0.0
(0.0v) and 1.0 (3.3v)
• A potentiometer “pot1” is connected to pin 19 of the mbed
NXP LPC1768
Challenge: DigitalOut and Analog Input
• Write a program to give the LED in the first blinky program a
delay of 0.1 - 1.0 seconds.
• Write a program that turns LED1 on at 0.66v, LED2 on at 1.32v,
LED3 on at 1.98v and LED4 at 2.64v
mbed
Hello World
Lab 3
Rapid Prototyping:
Interfacing a sensor
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Example : Interfacing with sensors
• A good deal of microcontroller applications require some form
of sensors to detect events or conditions in the immediate
environment.
• This experiment show how to implement a simple
temperature sensor.
• The sensor in question is the LM75B which has a digital
interface using the I2C bus.
Connecting up the sensor
• The LM75B has just four pins, Vcc, Gnd for the power, and
SCL, SDA for the I2C interface.
• As before, mbed keeps I2C simple, and online code reuse
helps out!
– http://mbed.org/handbook/I2C
– http://mbed.org/cookbook/LM75B-Temperature-Sensor
Challenge : Interfacing with sensors
• Using the mbed application board cookbook page as a
resource, write a program that turns LED1 on at 26^C, LED2 at
27^C, LED3 and 28^C and LED4 at 29^C.
• Note : To use “printf” in the hello world example, you will
need to install the mbed Serial port driver, and a terminal
application.
– See : http://mbed.org/handbook/SerialPC for details to set this up
mbed
Hello World
Lab 4
Rapid Prototyping:
Output device, LCD
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Example : Output device, LCD
• It is not uncommon for devices that are embedded to have
some for of user interface, or display output.
• This example shows how a LCD can be connected to mbed
and be driven simply form software.
Connecting up the LCD
• Text LCD modules have almost standardised, although they
still have their quirks.
– Six wires and a resistor for contrast
– As before, mbed keeps it simple
– Standard C/C++ interface via printf
• The mbed application board has a graphics LCD
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SPI interface with reset and chip select
Same API for character printing
Application code is the same!
http://mbed.org/cookbook/mbed-application-board
Challenge: Digital Thermometer
• Using the cookbook TextLCD page and the temperature sensor
page, make a thermometer that displays the current
temperature.
• If you have time, you could also add Min/Max to the display
too
mbed
Hello World
Lab 5
Rapid Prototyping:
Data Logging
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Example : Data Logging
• Applications often include data logging capabilities, and
access to the data often involves bespoke software and
interface cables.
• This example shows how standard methods and interfaces can
be used to display, save and retrieve data from an application
• For the purposes of the experiment, we will be displaying and
logging the value read from the potentiometer.
Example : See the data
• The USB connection to mbed can also
be used to provide a serial port
• Windows requires a driver, linux and
Mac “just work”
• http://mbed.org/handbook/SerialPC
• Standard C functions, printf and scanf
• This example displays 100 samples to a
terminal application
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http://mbed.org/users/chris/code/app-board-USB-printf/
Storing lots of data
• Perhaps a final system might want to store lots of data
– USB sticks ideal, ubiquitous and recognisable by everyone
– Minimal hardware : USB socket, 4 wires (Gnd, +5v, D+, D-)
– The mbed application board already provides this
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Storing lots of data
• mbed keeps it simple :
– Using the MSCFileSystem library
– Make and object called “fs”
– http://mbed.org/users/chris/code/app-board-MSCFileSystem/
Challenge: Data Logging
• Use all you have learnt to build a digital thermometer that
also data logs to a USB flash disk.
• Use a .csv file so that the file can be opened in Microsoft
Excel, and a graph drawn.
mbed
Hello World
Lab 6
Rapid Prototyping:
Offline debug with CMSIS-DAP
40
Debugging with CMSIS-DAP
• The online tools are designed for rapid prototyping
• Sometimes product development requires full debug
– Source code breakpoints
– Watch points
• mbed enabled microcontrollers support CMSIS-DAP
– Access to the DAP is provided over a driverless USB HID connection
– All leading tools support this new “debug probe” interface
– You can even write your own debugger (e.g. Python) to drive the DAP
• The mbed online tools enable you to export your project to an
offline tool (MDK, IAR, Crossworks, Code Red, etc)
Installing Keil MDK
• This lab assumes Keil MDK (currently Windows only)
• To download and evaluation copy of MDK, visit
https://www.keil.com/demo/eval/arm.htm
• Follow the install instructions
Upgrading your mbed NXP LPC1768
• By default, the mbed NXP LPC1768 is not CMSIS-DAP enabled
• Visit
http://mbed.org/handbook/Firmware-LPC1768-LPC11U24
• Save the upgrade file (version 141212 or later) to your mbed
• Power cycle your mbed, and you now have CMSIS-DAP
support
Exporting your mbed project
• For the purpose of this lab, we are using Keil MDK
• In the online compiler, right click your program, select “export”
• Unzip the downloaded project and click the .uvproj file to
launch Keil MDK
• For more information see
– http://mbed.org/handbook/CMSIS-DAP-MDK
Compile your program
• Click the compile button in the MDK IDE to build your project
• This example shows the default “blinky” program
Download your program
• Instead of drag and dropping your program, the MDK IDE can
load it to the LPC1768 over the CMSIS-DAP connection
Debugging your program
• Start a debug session
• (1) Add break points by clicking on the line of code you wish
to stop at. There are a maximum of 2 breakpoints
• (2) and use the "run" button to execute the program until the
Start debug session
break point it hit.
Debug features
• Use the tool bar to add other debug feature to the IDE
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Registers : The values in the CPU registers at the breakpoint
memory : View the current contents of RAM
call stack : The sequence of function call that lead to the breakpoint
Symbol : View (and modify) current variables
mbed
Hello World
Summary
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Summary
• There is huge opportunity for microcontroller applications
– A major barrier to adoption is simple experimentation
• mbed helps with getting started and rapid prototyping
– Fast turnaround of experiments and prototyping new ideas
– Try out new technology and new ideas
• Makes the technology very accessible
– Demo showed a start to finish prototyping example
– From getting a user started to enabling an application experiment
• Use at as a tool when you need to experiment!
Summary
• A solution focused on prototyping has a broad appeal
• Engineers new to embedded applications
– Enables experimentation and testing product ideas for the first time
– Create designs where electronics and MCUs are not the focus
• Experienced engineers
– Provides a way to be more productive in the proof-of-concept stages
– Introduce 32 bit microcontroller technology to existing designs
• Marketing, distributors and application engineers
– Provides a consistent platform for demonstration, evaluation, support
– Make promotion of MCUs more effective and efficient
Q&A
Slides available at …
http://mbed.org/cookbook/Workshop
Under “ARM University Program”
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