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Programming embedded systems

Seminar 1

INTRODUCTION

Dr. Tran Thanh Hung

Department of Automation Technology,

College of Engineering, Can Tho University

Email: tthung@ctu.edu.vn

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Outline

Seminar objectives

Embedded system: What is it?

Course overview

Why C?

Why MSP430?

Hardware & Software required

Simple software architecture

Examples

Software delay

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Seminar objectives

At the end of this seminar, by referring the lecture

notes, students will be able to:

know the course objectives

identify the requirements for an embedded system explain why MSP430 and C are chosen for embedded

system development

explain the relationship between C, assembly, and

machine languages know the basic features of MSP430

write a simple software to run a task

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What is an embedded system?

An embedded systemis a computer systemdesigned for one or few application.

Which components does an embeddedsystem consist of?

http://en.wikipedia.org/wiki/Computer_systemhttp://en.wikipedia.org/wiki/Computer_system

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Core of embedded system

MCU = MicroController Unit

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Applications of embedded system

Mobile phone systems

Automotive applications

Domestic appliances Aerospace applications

Medical equipment

Defence systems

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Course overview

This course will introduce the principles of

programming for embedded systems.

By the end of this course, you will be able to:

Know how to build an embedded system

Design embedded software for a simpleapplication

Implement and test designed software

Understand issues of reliability and safety

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Textbooks

1. Embedded C by Michael J. Pont

2. MSP-EXP430G2 LaunchPad Experimenter

Users Guide3. Code Composer Studio Users Guide

4. MSP430G2435 Datasheet

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How computers were built?

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Which programming language

should you use?

Remember:

CPU/MCU can only understand programs in machinelanguage

All programs need to be translated to machine code Need a good translator software: translate correctly

what you write

Power and memory of MCU are limited: language must

be efficient For programming embedded system, you need low-

level access to hardware

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Why C?

A mid-level:- support functions

- access hardware

Independent to device High efficient

Popular

Easy to understand Good compilers

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Can we build CPU/MCUs that can

understand high-level language?

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Can we build CPU/MCUs that can

understand high-level language?

Thats means:

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Why MSP430?

How to chose MCU for an embedded system?

Some famous MCUs:

+ Z80 (8bit) designed by Zilog from 1976: needs too

many clock periods to run an instruction

+ 8051 (8bit) series (or MSC-51) developed by Intel

from1980: one of the first single chip microcontrollers,

needs 12 clock periods to run an instruction

+ AVR (8bit-RISC) developed by Atmel in 1996,

integrates ADC and many other components, most

instructions run in 1 clock period

+ MSP430 (16bit-RISC) developed by Texas Instrument

from 1990s

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Why MSP430?

In this course, MSP430 family is chosen,because:

- Price: very cheap- Available: very famous, easy to find

- Performance: powerful, ultra low-power,

suitable for many embedded systems- Wide range: many MCUs to choseSee http://www.ti.com/msp430

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Hardware & Software required

MSP430 LaunchPad

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Hardware & Software required

Software required:

- Code Composer Studio (CCS)

- Or IAR Embedded Workbench

See http://focus.ti.com/docs/toolsw/folders/print/msp-exp430g2.html#0

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MSP430 Block Diagram

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MSP430 Characteristics

16 bit RISC CPU, up to 25 Mhz Clock

Ultra low power consumption:

0.1 A for RAM data retention

0.8 A for real-time clock mode operation

250 A/MIPS during active operation

Low operation voltage: 1.8V3.6 V

Up to 256K Bytes of In-System Programmable(ISP) Flash Memory

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MSP430 Characteristics

Pin-outs from 14 pins up to 100 pins

Most pins have multiple features (pinmultiplexing)

On-chip analogue devices: ADC, DAC

Embedded Debug/Emulation capability (JTAG)

Many 16-bit Timer/Counters Many Interrupt Sources

Serial Interface: SPI, I2C

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Simple software architecture

What is the minimum software environmentyou need to run a task X()?

void main (void){

X_Init() ; //Prepare for Task X()

while(1) //super loop

{

X(); //Perform task X()

}

}

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Simple software architecture

What are strengths of super loops ?

- Very simple, easy to build, debug, test, and maintain

- High efficient: use minimum hardware

- Highly portable

BUT: What are the weakness ?

- Not suitable for applications required accurate timing

- Full power consumption

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Example 1.1: Flashing a LED

#include msp430g2452.h

void main(void)

{WDTCTL = WDTPW + WDTHOLD; // Stop watchdog timer

P1DIR |= 0x01; // Set P1.0 to output direction

while(1)

{

P1OUT ^= 0x01; // Toggle P1.0 using exclusive-OR

}

}

How to write a software to turn on/off a LED connected to P1.0?

Can you see the LED blink? Why?

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Example 1.2: LED runs

#include msp430g2452.h

void main(void)

{ unsigned int i;

WDTCTL = WDTPW + WDTHOLD; // Stop watchdog timer

P1DIR |= 0xFF; // Set P1 to output directionwhile(1)

{

for (i = 0;i

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Software delay

void loop_delay(void)

{

unsigned int x;

for (x = 0; x

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Software delay

What are strengths of software delay ?

- Can be used to create very sort delays

- Require no hardware

- Will work on any microcontroller

BUT: What are the weakness ?

- Very difficult to create precisely time delays

- Need to be re-tuned if you change microcontroller, or

clock frequency, or compiler optimization settings

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Conclusion

Seminar objectives

Embedded system: What is it?

Course overview

Why C?

Why MSP430?

Hardware & Software required

Simple software architecture

Examples: Central heating system; access input,output

Software delay

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Bi tp 1.0

1. Ci t phn mm Code Composer Studio V.4

2. Tm hiu phn mm Code Composer Studio:

- Cc menu, ca s

- Cch to project, bin dch (build), debug (tronghelp contents)

- Common Debug Actions

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Bi tp 1.1

To project Baitap1_1

Chn thit b MSP430G2452 cho DeviceVariant

To source file baitap1_1.c, nh li ni dungtrong Example 1.1

Bin dch v Debug chng trnh

Chy tng lnh chng trnh, quan st LED Chy chng trnh lin tc, quan st LED

Thay i chng trnh LED chp tt 1

ln/giy

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Bi tp 1.2

To project Baitap1_2

Chn thit b MSP430G2452 cho DeviceVariant

To source file baitap1_2.c, nh li ni dungtrong Example 1.2

Bin dch v Debug chng trnh

Chy tng lnh chng trnh, quan st LED Chy chng trnh lin tc, quan st LED

Thay i chng trnh thy c LED chy

ui

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Bi kim tra 1.1

1. Lit k cc thnh phn chnh ca mt h thng nhng.

2. Ti sao MSP430 v C c chn pht trin hthng nhng?

3. Mi quan h gia C, hp ng v ngn ng my thno?

4. Dng Code Composer Studio, tm on m tngng bng hp ng v m my ca 1 vng for trong

hm delay.

5. Ti sao chng ta cn dng siu vng lp thc hinmt cng vic?

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T hc (5G)

Khm ph cc tnh nng cn li ca CCS

c file Code Composer Studio Users

Guide