Design and Development of ARM based Embedded system

Design and Development of ARM based Embedded system
Design and Development of ARM based
Embedded system Laboratory
Aruna. Kommu and Raghavendra Rao. Kanchi
VLSI and Embedded System Laboratory
Department of Physics, Sri Krishnadevaraya University.
Anantapur, 515003, Andhra Pradesh, India
* [email protected]
Abstract— In this paper we present a platform consisting of a
series of laboratory exercises using ARM microcontrollerLPC2148 (ARM&TDMI). The open hardware system in the
present scenario gives an opportunity to perform the
experiments even at home. Stress is given to the simple
representation in terms of block diagrams instead of the use of
high level tools (C or Assembly). The system described supports
the transfer of developed program code from Laptop to the
Microcontroller, and evaluation of its execution on rapid
prototyping hardware. Further it allows the students to add new
exercises to the already existing list. They can also enhance their
skills by developing software which is suitable for hardware
interfacing and data acquisition in the laboratory. The series of
experiments described in the present paper will be a point of take
off to start a journey on working in the area of embedded system.
It gives an opportunity to think individually and to develop the
creativity towards the fast growth of technology about an
embedded system. Suggestions are given in the design so that
incorrect wiring and testing will be avoided.
on which a series of experiments can be performed that gives
a hands –on experience and bringing in a take home concept.
Further, the series of experiments described in this paper can
be introduced as a part of curriculum for the senior graduate
students.
A.ARM7TDMI
ARM (Advanced RISC Machine) architecture is the 32 bit
RISC instruction set architecture which is most widely used in
a number of embedded systems. ARM is a leading intellectual
property provider of high performance, low cast, and power
efficient RISC processor microcontroller [3]. ARM processor
has some characteristics that made them suitable for low
power application such as intelligent voltage management and
cache micro architecture. The most prominent future that
makes ARM differ from other microcontrollers is [4]:
Interrupt system
cache controller design
voltage management
Instruction set.
I. INTRODUCTION
ARM CPU has a von Newman architecture and it uses two
In the present scenario, topics like: Application Specific buses i.e. AHB (advanced high performance bus) and VPB
Integrated Circuit (ASIC), System- on Chip (SOC) have (VLSI peripheral bus) which increases the speed of execution
replaced Computer Architecture, Organization and design in [5] compared to other commonly used microcontroller such as
the field of Computer Engineering. This shift has called for the INTEL 8051 and the Microchip PIC family. ARM family
want of knowledge on Embedded System to be a pre-requisite. provide wide range of performance from 100 MIPS to 1000
Majority of universities in India offers courses on MIPS. This increase in performance leads to two important
microcontrollers like PIC, ATMEL, MOTOROLA, INTEL etc. factors and advances in a new process technology.
Few universities in India have taught ARM microcontroller in
New pipeline mechanism.
their curriculum. There are several papers dealing with
Implementation of Harvard bus architecture in ARM9
development of laboratory experiments using different
family
platforms and different microcontrollers [1, 2]. Paper
An efficient and optimized processor design is an art. This is
dealing with development of laboratory exercises using ARM- because the instruction set should cater the need of the
based microcontroller are very less. On the other hand there is programmer in an efficient way. i.e. keeping the future
a vast development of technology with high performance implementation also plays pivotal role in the processor
microcontroller like ARM and on software side the operating design .This is because it has to bridge the gap between HLL
system Windows 8 can run on ARM microcontroller has been construct and machine language. Thus the compiler design
developed.ARM microcontroller is dominant in the mobile which in turn depends on the type of instruction set. The
and auto mobile electronics market and is one of the industry whole ARM family has the same instruction set of 32 bit
leading standard microcontroller. This is compatible with all ARM instruction set and 16 bit thumb instruction set .The
four major platform operating systems Symbian os, Palm os, thumb instruction set was introduced in the fourth version of
Linux os and windows CE. Keeping the above facts in view the ARM architecture in order to achieve the high code
point, we thought that it is worthwhile to describe a platform density for embedded applications.
Keywords— ARM7TDMI, LPC2148, On-chip Peripherals, Realtime Interfacing, Hands –on experiences.
NXPs ARM mini kit was purchased from NSK electronics
which cost about 30$ [6]. Mini ARM kit consists of LPC2148
ARM7TDMI as its core and two types of memory, Flash
memory of 512kb with In system program and In Application
programming, static RAM of 40kb [7]. LPC2148 CPU has a
simple programmer model and it has sixteen 32 bit general
registers and two special registers named as current program
status register (CPSR), saved program status register (SPSR).
It has a vectored interrupt controller, two 10 bit ADCs with 14
channels, one DAC.USB full speed device controller, two
UARTS one with full modem interface, two 32 bit timers,
watch dog timer, PWM unit, REAL time clock with optional
battery backup and 45 general purpose i/o pins, CPU clocks
up to 60MHz on chip crystal oscillator and on chip PLL.
There is open source KEIL software that provides a best
development tool and technical support [8]. It also offers
numerous ways from the technical support that one needs to
complete embedded projects. KEIL supports simulation using
the target systems and a debugger interface. Micro vision
includes traditional features like simple and complex
breakpoints, watch windows and execution controls as well as
sophisticated features like trace capture, execution profiler,
code coverage and logic analyser. Features such as free
development tools and compilers plus the ability to integrate a
low cost in circuit debugger in to the ARM CPU module made
the ARM an excellent choice for the new advances that have
been made in new process technologies. ARM CPUs accounts
for approximatly75% of all embedded 32-bit RISC CPU
making it the worlds largest selling 32-bit architecture. This
allows the students to learn popular microcontroller
architecture in their gradual level which is widely used in the
electronics industry. When the ARM CPUs are designed
ARM7TDMI from ARMv5 was the most popular device used
in Apple iPod and Newton PDA. TheARM7 microcontroller
also provides a wide range of internal peripherals. All these
features have made the ARM7 an ideal choice for lab
experimental kit for the beginners in to ARM microcontroller.
Some of the embedded control application typically requires a
processor with cache and memory protection to utilize the real
time operating systems. The vast majority of users need
security and desktop/web productivity applications. For that
purpose ARM has developed a vertical expansion of CPUs to
match the user requirements and provides a unique,
configurable amount of cache. Recent development includes a
new pipeline mechanism and implementation of Harvard
architecture in ARM9 family, DSP and java extensions to
some of the new architecture enables rich applications to
benefit from the high performance and low power
consumption intrinsic to ARM processor cores. BY
considering the above all facts ARM architecture is
compatible, flexible and encompass the full range of
embedded requirements, we have chosen to popularise ARM
microcontroller by developing a series of experiments useful
for graduate level laboratory. The following sections give an
account of experiments performed in the laboratory.
II. EXPERIMENTAL DESCRIPTION
In our department embedded laboratory consisted of a
series of experiments using PIC, Atmel and Intel
microcontrollers. For the reason that ARM microcontrollers
have become very popular in mobile technology, automobile
and electronic industry, it is felt to introduce ARM based
training in hardware and software for the first time in the
curriculum. In this direction, a series of experiments useful to
both undergraduates and graduate laboratories of engineering
and science have been designed and developed. One of the
advantages of the described experiments is that they can be
implemented even for take-home labs since the hardware
components are inexpensive. The experiments are provided
with the relevant documentation. Brief description of these
experiments is given in the following. Fig 1 shows the mini
ARM kit connected to laptop.
Fig1: The mini ARM kit connected to the laptop and program uploading
window
A. LOGIC CONTROLLER
The first experiment is to get acquainted with the
programming of a port of the Lpc2148 as input/output. This
needs the careful study of the I/O pins and selection of their
function. The logic controller experiment comprises of
interfacing LEDs with output port and connecting a
pushbutton(s) to an input port.
Output port: LEDs are connected to PORT of LPC2148 and
software is developed to switch alternate LEDs on and off,
and different variants of this exercise.
Input port: A single push-button (PB) is connected to one of
the pins of port 0 and that bit which PB is connected is
programmed as input port and software is developed to
display the number of times the push button is pressed on
LCD (interfacing LCD with LPC2148) is explained in
exercise B
B. INTERFACING LCD
This experiment gives the hardware and software description
to interfacing LCD (16charactersx2line) with an output port.
In fact, the LCD can be interfaced in two modes: 8-bit mode
and 4-bit economic mode. In the present experiment the
second technique is explained since this presents a mode of
optimal utilization of I/O port pins. Following fig 2 shows the
LCD module interfaced with ARM CPU.
the amount of power applied to the motor. This can be varied
by the technique: pulse width modulation. LPC 2148 provides
a multiplexed pin as PWM output. Hardware is developed in
the form of a power amplifier with H-bridge that provides an
opportunity to rotate the motor clock-wise and anti clock-wise
directions. Software for obtaining variable duty cycle and
hence motor to rotate at different speeds is realized.
F. INTERFACING RELAYS AND SOLENOIDS
Interfacing of relays and solenoids with the output ports of
lpc2148 throws light on control applications such as
temperature control, flow control etc. These relays solenoids
are interfaced via buffer/power amplifier stage. Software
controls the on/off time in a programmed way.
G. ANALOG VOLTAGE MEASUREMENT USING ON-CHIP
ANALOG-TO-DIGITAL CONVERTER (ADC):
Lpc2148 is fabricated with a 10 bit on chip ADC. It can be
used in single ended/differential mode of operations. In the
present exit intensity measurement is carried out by
interfacing a photodiode with the analog input of ADC. LED
intensity is varied by an automated potentiometer driven by a
potentiometer. The acquired data is plotted by the computer
using origin package.
H. GENERATION OF ANALOG VOLTAGE USING ONCHIP DIGITAL-TO-ANALOG CONVERTER (DAC):
Fig 2: LCD module interfaced with ARM CPU
C.
INTERFACING
MODULE
SEVEN-SEGMENT
DISPLAY
A 4-digit LCD display module is interfaced with LPC 2148.
The display is driven by to ULN 2003 (Darlington Pair IC)
and multiplexed display concept is implemented by software.
This ensures low power consumption by the LED display
module. The outcome of the experiment is: To understand the
concept of multiplexed display.
D. INTERFACING STEPPER MOTOR
A stepper motor collected from a junked 51/4 floppy drive is
used. This experiment demonstrates the use of stepper motor
for different applications by rotating to motor of different
angles and different speeds. The stepper motor is driven by an
output via power driven IC ULN 2003.This experiment paves
path for applications of stepper motor rotation for different
applications.
E. INTERFACING DC MOTOR
A DC motor unlike stepper motor rotates continuously on the
application of power to it. The speed of rotation depends on
The on chip DAC of LPC2148 can be used for various
applications such as waveform generation, displaying alphanumeric and graphics, generating different values of analog
output voltages etc .In the present work different analog
output voltages are measured by giving different digital inputs
at the appropriate digital pins that are selected using the pin
functions corresponding to DAC
I. REAL TIME CLOCK
The on chip RTC is useful in serial applications such as to
count the happening of events, ultra low power design to
support battery powered systems. In the present experiment
software is developed to display Date, month, year and time
on the LCD which is interfaced in the experiment B. The
experimental arrangement using LPC2148 is shown in fig 3.
J.UNIVERSALASYNCHRONOUSRECEIVER/
TRANSMITTER (UART):
LPC2148 has two on chip UARTs. One of these UARTs is
used. Software is developed to send characters to laptop under
HyperTerminal. This experiment gives an insight in to the
serial interface protocol-RS232, Baud rate selection etc.
REFERENCES
[1]
[2]
[3]
[4]
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Fig: 3 Displaying real time clock on LCD module
H. SERIAL PERIPHERAL INTERFACE (SPI):
The on chip SPI of lpc2148 uses MOSI, MISO, SCLK, and
SSEL. Pin functions are selected to interface a 12-bit ADC
(MCP3204), which supports SPI protocol. The digital output
equivalent to analog input voltage is displayed on LCD screen.
As shown in fig 4.
Figure 4 Interfacing MCP3204 (ADC) with ARM Module under SPI Protocol
III. CONCLUSION
A series of experiments were designed using ARM platform.
They can be incorporated in the engineering and science
discipline. The low cast and fully open structure of the ARM
is considered to make it a good embedded platform, especially
in the higher education curriculum. With this basic and
fundamental knowledge of experimental lab using ARM,
students can learn the real engineering challenges by
experiencing hardware design, hardware prototyping and
sensor connectivity in addition being able to control various
signals in a single programming environment. It also allows
the students to improve their programming knowledge by
engaging them in real experiments. Using this approach it
also provides a fast learning process since it gives the
opportunity to work with the experimental modules whenever
needed.
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