embedded notes.iet.trichy

Singaperumal Thayar Thunai

INNOVATIVE ELECTRICAL TECHNOLOGIES Shaping Quality Engineers

____________________________________________________________________________

EMBEDDED

1. OVER VIEW OF EMBEDED SYSTEM

1.1System

1.2Embedded System

1.3Components of Embedded System

1.4Embedded System Hardware

1.5Developing Embedded System

2. HARDWARE DESIGN

2.1 Microcontroller

2.2 Processor

2.3 Controller and Processor Comparison

2.4 Popular Microcontrollers

2.5 Power Supply Section Designing

2.6 Signal Generation with Speed of Frequency

3. MICROCONTROLLER 8051

3.1 Basic Components of 8051

3.2 Features of 8051

3.3 Pin diagram

4. PIC MICROCONTROLLER

4.1 Features of PIC


4.2 Pin Diagram

4.3 Pin Description

5. EMBEDDED C

5.1 Introduction of Embedded C

5.2 Failing of Hardware

5.3 Avoiding the Failure

5.4 Common Aim of Coding Standard

5.5 Sample Rules of Coding Standard

5.6 Example Programs

5.7 Exercise Programs


Chapter 1: OVER VIEW OF EMBEDDED SYSTEM

1.1 SYSTEM

A system is a way of working, organizing or doing one or many tasks according to a

fixed plan, program or set of rules. A system is also an arrangement in which all its units

assemble and work together according to the plan or program.

Example:

1. WATCH

It is a time display SYSTEM

Parts: Hardware, Needles, Battery, Dial, Chassis and Strap.

Rules

All needles move clockwise only

A thin needle rotates every second

A long needle rotates every minute

A short needle rotates every hour

All needles return to the original position after 12 hours.

2. WASHING MACHINE

It is an automatic clothes washing SYSTEM

Parts: Status display panel, Switches & Dials, Motor, Power supply & control unit, Inner water

level sensor and solenoid valve.

Rules

Wash by spinning


Rinse

Drying

Wash over by blinking

Each step display the process stage

In case interruption, execute only the remaining

1.2 EMBEDDED SYSTEM

An embedded system is a special purpose system that is used to perform one or few

dedicated functions. Simply, we can call any electronic device that has a computer system

embedded inside it an embedded system.

An Embedded System is one that has computer hardware with software embedded in it as

one of its important components.

Some examples of embedded systems are:

1. Alarm / security system

2. Automobile cruise control

3. Heating / air conditioning thermostat

4. Microwave oven

5. Anti-skid braking controller

6. Traffic light controller

7. Vending machine

8. Gas pump

9. Handheld Sudoku game


10. Irrigation system controller

11. Singing wall fish (or this gift season’s equivalent)

12. Mars Rover

Embedded systems are made to perform few tasks only, after implementation you can’t

use them for another purposes.

Ex: You can’t watch movies using the microprocessor of your microwave oven!!

1.3 COMPONENTS OF EMBEDDED SYSTEM

It has Hardware

They are processor, Timers, Interrupt controller, I/O Devices, Memories, Ports,

etc.

It has main Application Software

That may perform concurrently the series of tasks or multiple tasks.

It has Real Time Operating System (RTOS)

RTOS defines the way the system work which supervise the application software.

It sets the rules during the execution of the application program. A small scale

embedded system may not need an RTOS.


1.4 EMBEDDED SYSTEM HARDWARE

1.5 DEVELOPING EMBEDDED SYSTEMS

Embedded System Development

Software Development

Hardware Development


Chapter 2: HARDWARE DESIGN

2.1 MICROCONTROLLER

It’s a full computer system on a chip, even if its resources are far more limited than of a

desktop personal computer designed for standalone operations. So.. What’s the difference

between a microcontroller and a microprocessor system?

A microcontroller has a processor and many peripherals integrated with it on the same chip, like a

flash memory, RAM, I/O ports, serial communication ports, ADC, Etc.


A timer module to allow the MCU to perform tasks for certain time periods.

A serial I/O port to allow data to flow between the MCU and other devices such as a PC or

another MCU.

An ADC to allow the MCU to accept analog inputs for processing.

But a microprocessor can’t do all the functions of a computer system on its own, and

needs another circuits to support it like: I/O devices, RAM, ROM, DMA controllers,

Timers, ADC, LCD drivers.. Etc.

2.2 PROCESSOR

Program Flow and data path Control Unit (CU):

That includes a fetch unit for fetching instructions from the memory.

Execution Unit (EU):

Includes circuits for arithmetic and logical unit (ALU), and for instructions for a program

control task, say, data transfer instructions, halt, interrupt, or jump to another set of instructions

or call to another routine or sleep or reset.


2.3 CONTROLLER AND PROCESSOR COMPARISION

2.4 POPULAR MICROCONTROLLERS

8051 (Intel and others)

80386 EX (Intel)

PIC (Microchip)

68HC05 (Motorola)

Z8 (Zilog)

COMPARISION

Microcontroller General purpose Microprocessor

Depend mainly on its peripherals like:

Program memory, I/O ports, timers, interrupt

circuitry, ADC, Etc.

Depend mainly on other devices like:

I/O devices, memory, DMA controllers, Etc.

Used for a few dedicated functions determined by

the system designer.

Used in many applications, according to the

program running on it

Usually used as a part of a larger system It’s in the heart of our PC’s


2.5 POWER SUPPLY SECTION DESIGNING

You need to hook up 5V and GND to your micro. Your house outlet runs at 220V AC

and is very bad for 5V DC (direct current) micros. So you'll need to convert the 220V AC from

your outlet to a useable 5V DC.

If you reverse the connection on your micro - bad things happen. Always make sure your

5V power supply is connected to the VCC pins and GND to GND. If you reverse this and

connect 5V to GND on the micro and GND to VCC on the micro, things won't explode, probably

no smoke, things will probably heat up like crazy.

Before the regulator circuit, the 220V AC converted to 9V DC by using adapter. Then the

9V converted to 5V DC by the regulator circuit. The most common regulator is called the

LM7805.

We can simply connect the terminals of the regulator LM7805 like in above circuit but

there is some noise in the input pin. That noise may affect the output voltage so we should use

filtering capacitors to get better output voltage.


Another thing is, while designing the circuit as a beginner there may be a chance of

making mistakes in designing so if any things heat up/smoke/spark, just unplug or turn off the

system. So we need an on/off power switch/relay. Now the circuit modified as below.

Remember all the warning about reversing VCC and GND and how that is bad? Well if

you connect your power supply backwards, that's bad. So let's protect ourselves!

Note that the diodes are polarized. Hence the diode can avoid reverse current.

Let us see how to connect the LED with this regulator circuit. If you connect the LED

like in above circuit the LED will glow much brighter but burn out. The LED is a diode it can

withstand only 20mA. So here we should use ohms law (V=IR) to calculate the resistance value

to drop voltage and maintain the current 20mA. The calculation as follows,

V = IR (this is Ohm's law)

If we have 5V, and we only want 20mA flowing through the LED:

5V = 0.02 * R

R = 250 Ohm

Now this is not completely true because the LED has a forward voltage drop. But don’t

worry about that we can use 220 ohm, 330ohm and 1k.The final proper circuit is given below,


2.6 SIGNAL GENERATION WITH SPEED OF FREQUENCY

Calculation of Machine Cycle for 8051:

The formula for calculating the machine cycle is given by,

Machine cycle=1/(Fosc/12).

Find the machine cycle for

Fosc = 11.0592 MHz

Fosc = 16 MHz

Solution:

1). 11.0592 MHz / 12 = 921.6 kHz;

Machine cycle = 1 / 921.6 kHz = 1.085 s

2). 16 MHz / 12 = 1.333 MHz;

Machine cycle = 1 / 1.333 MHz = 0.75 s


Calculation of Machine Cycle for PIC16f877A:

The formula for calculating the machine cycle is given by,

Machine cycle=1/(Fosc/4).


Chapter 3: MICROCONTROLLER 8051

3.1 BASIC COMPONENTS OF 8051

4K bytes internal ROM

128 bytes internal RAM

Four 8-bit I/O ports (P0 - P3).

Two 16-bit timers/counters

One serial interface.

3.2 FEATURES OF 8051

only 1 On chip oscillator (external crystal)

6 interrupt sources (2 external , 3 internal, Reset)

64K external code (program) memory(only read)PSEN

64K external data memory(can be read and write) by RD,WR

Code memory is selectable by EA (internal or external)

We may have External memory as data and code.


3.3 PIN DIAGRAM

One of the most useful features of the 8051 is that it contains four I/O ports (P0 - P3)

Port 0 （pins 32-39）：P0（P0.0～P0.7）

8-bit R/W - General Purpose I/O

Or acts as a multiplexed low byte address and data bus for external memory

design

Port 1 （pins 1-8）：P1（P1.0～P1.7）

Only 8-bit R/W - General Purpose I/O

Port 2 （pins 21-28）：P2（P2.0～P2.7）

8-bit R/W - General Purpose I/O

Or high byte of the address bus for external memory design

Port 3 （pins 10-17）：P3（P3.0～P3.7）

General Purpose I/O


If not using any of the internal peripherals (timers) or external interrupts.

Each port can be used as input or output (bi-direction).

The port3 has alternative functions as follows.


Chapter 4: PIC MICROCONTROLLER

4.1 FEATURES OF PIC

There are varieties of choice in PIC from 8 bit to 32 bit.

Low Power

Reasonable Size

Convenient Packaging

Through Hole (Dip)

Surface Mount (QFN/SPDIP)

Resources and References

Sleep mode

Watchdog timer (WDT)

Code protection

In-circuit serial programming

In-circuit debugger


4.2 PIN DIAGRAM

Pin diagram of PIC16F877A.

4.3 PIN DESCRIPTION

As seen in Figure above, the most pins are multi-functional. For example, designator

RA3/AN3/Vref+/C1IN+ for the fifth pin specifies the following functions:

RA3 Port A third digital input/output

AN3 Third analog input

Vref+ Positive voltage reference

C1IN+ Comparator C1positive input


This small trick is often used because it makes the microcontroller package more

compact without affecting its functionality. These various pin functions cannot be used

simultaneously, but can be changed at any point during operation.

PIC16F877 has 5 basic input/output ports. They are usually denoted by PORT A (R A),

PORT B (RB), PORT C (RC), PORT D (RD), and PORT E (RE). These ports are used for input/

output interfacing. In this controller, “PORT A” is only 6 bits wide (RA-0 to RA-7), ”PORT B” ,

“PORT C”,”PORT D” are only 8 bits wide (RB-0 to RB-7,RC-0 to RC-7,RD-0 to RD-7),

”PORT E” has only 3 bit wide (RE-0 to RE-7).

PORT-A RA-0 to RA-5 6 bit wide

PORT-B RB-0 to RB-7 8 bit wide

PORT-C RC-0 to RC-7 8 bit wide

PORT-D RD-0 to RD-7 8 bit wide

PORT-E RE-0 to RE-2 3 bit wide

All these ports are bi-directional. The direction of the port is controlled by using TRIS(X)

registers (TRIS A used to set the direction of PORT-A, TRIS B used to set the direction for

PORT-B, etc.). Setting a TRIS(X) bit ‘1’ will set the corresponding PORT(X) bit as input.

Clearing a TRIS(X) bit ‘0’ will set the corresponding PORT(X) bit as output.

(If we want to set PORT A as an input, just set TRIS(A) bit to logical ‘1’ and want to set PORT

B as an output, just set the PORT B bits to logical ‘0’.)

Analog input port (AN0 TO AN7) : these ports are used for interfacing analog inputs.

TX and RX: These are the USART transmission and reception ports.

SCK: these pins are used for giving synchronous serial clock input.

SCL: these pins act as an output for both SPI and I2C modes.

DT: these are synchronous data terminals.


CK: synchronous clock input.

SD0: SPI data output (SPI Mode).

SD1: SPI Data input (SPI mode).

SDA: data input/output in I2C Mode.

CCP1 and CCP2: these are capture/compare/PWM modules.

OSC1: oscillator input/external clock.

OSC2: oscillator output/clock out.

MCLR: master clear pin (Active low reset).

Vpp: programming voltage input.

THV: High voltage test mode controlling.

Vref (+/-): reference voltage.

SS: Slave select for the synchronous serial port.

T0CK1: clock input to TIMER 0.

T1OSO: Timer 1 oscillator output.

T1OS1: Timer 1 oscillator input.

T1CK1: clock input to Timer 1.

PGD: Serial programming data.

PGC: serial programming clock.

PGM: Low Voltage Programming input.

INT: external interrupt.

RD: Read control for parallel slave port.

CS: Select control for parallel slave.

PSP0 to PSP7: Parallel slave port.

VDD: positive supply for logic and input pins.

VSS: Ground reference for logic and input/output pins.


Chapter 5: EMBEDDED C

5.1 INTRODUCTION OF EMBEDDED C

In embedded programming usually programmer have to be much more aware of the

resources consumed in embedded systems programming than you have to in “ordinary”

programs time, space, communication channels, files, ROM (Read-Only Memory), Flash

memory, etc..

Programmer must take the time to learn about the way your language features are

implemented for a particular platform hardware, operating system and Libraries.

A lot of this kind of programming is looking at specialized features of an RTOS (Real

Time Operating System), Using a “Non-hosted environment” (that’s one way of saying “a

language right on top of hardware without an operating system”), Involving (sometimes

complex) device driver architectures and Dealing directly with hardware device interfaces.

5.2 FAILING OF HARDWARE

In general, we cannot know how the failing happening was. In practice, we can assume

that some kinds of errors are more common than others but sometimes a memory bit just decides

to change. Why because there is more number of failure can occur,

Power surges/failure

The connector vibrated out of its socket

Falling debris

Falling computer

X-rays


The transient errors are the worst (E.g., only when the temperature exceeds 100° F. and

the cabinet door is closed) and the errors that occur away from the lab are the worst (E.g., on

Mars).

5.3 AVOIDING THE FAILURE

Replicate -> In emergency, use a spare

Self-check-> Know when the program (or hardware) is misbehaving

Have a quick way out of misbehaving code ->Make systems modular, Have some other

module, computer, part of the system responsible for serious errors, In the end, maybe a person

i.e., manual override.

Monitor (sub) systems-> In case they can’t/don’t notice problems themselves

5.4 COMMON AIM OF CODING STANDARD

Reliability

Portability

Maintainability

Testability

Reusability

Extensibility

Readability


5.5 SAMPLE RULES OF CODING

No function shall have more than 200 lines (30 would be even better) that is, 200

non-comment source lines

Each new statement starts on a new line (E.g., int a = 7; x = a+7; f(x, 9); //

violation!)

No macros shall be used except for source control (using #ifdef and #ifndef

Identifiers should be given descriptive names)

May contain common abbreviations and acronyms

When used conventionally, x, y, i, j, etc., are descriptive

Use the number_of_elements style rather than the numberOfElements style

Type names and constants start with a capital letter(E.g., Device_driver and

Buffer_pool )

Identifiers shall not differ only by case (E.g., Head and head // violation!)

Identifiers in an inner scope should not be identical to identifiers in an outer scope

(E.g., int var = 9; { int var = 7; ++var; } // violation: var hides var )

Declarations shall be declared in the smallest possible scope

Variables shall be initialized (E.g., int var; // violation: var is not initialized)

Casts should be used only when essential

Code should not depend on precedence rules below the level of arithmetic

expressions (E.g., x = a*b+c; // ok)

if( a<b || c<=d) // violation: parenthesize (a<b) and (c<=d)

Increment and decrement operations shall not be used as sub expressions (E.g.,

int x = v[++i]; // violation (that increment might be overlooked))


5.6 EXAMPLE PROGRAMS

1). Requirement: LED blinking- 8 LEDs are connected in PORTB.

Coding:

void main()

{

TRISB = 0; // set direction to be output

do

{

PORTB = 0x00; // Turn OFF LEDs on PORTB

Delay_ms(1000); // 1 second delay

PORTB = 0xFF; // Turn ON LEDs on PORTB

Delay_ms(1000); // 1 second delay

} while(1); // Endless loop

}

2).Requirement: Running glow of LEDs- 8 LEDs connected in PORTA

Coding:

char counter;

void wait()

{


Delay_ms(100);

}

void main()

{

TRISA = 0x00; // set direction to be output

PORTA = 0x00; // turn OFF the LATD leds

while (1)

{

for (counter=0; counter<8; counter++)

{

PORTA |= 1 << counter;

wait();

}

counter = 0;

while (counter<8)

{

PORTA &= ~(1 << counter);

wait();

counter++;

}

}


}

3).Requirement: Controlling the LEDs by using a switch. 4 LEDs are connected in PORTC

and a switch connected in PORTB.

Coding:

char oldstate; // Old state flag

void main()

{

TRISB0_bit = 1; // set RB0 pin as input

TRISC = 0x00; // Configure PORTC as output

PORTC = 0xAA; // Initial PORTC value

oldstate = 0;

do

{

if (Button(&PORTB, 0, 1, 1)) // Detect logical one

{

oldstate = 1; // Update flag

}

if (oldstate && Button(&PORTB, 0, 1, 0)) // Detect one-to-zero transition

{

PORTC = ~PORTC; // Invert PORTC


oldstate = 0; // Update flag

}

} while(1); // Endless loop

}

4).Requirement: LED blinking using timer interrupt. 6 LEDs are connected in PORTB.

Coding:

unsigned char timerint=0;

void main()

{

PORTB=0;

TRISB=0xc0;

PIR1.f0=0;

PIE1.f0=1;

INTCON=0xc0;

T1CON=0x01;

while(1)

{

if(timerint)

{

PORTB=~PORTB;


timerint=0;

}

}

}

void interrupt()

{

if(PIR1.f0)

{

timerint=1;

PIR1.f0=0;

TMR1L=TMR1L+176;

TMR1H=TMR1H+60;

}

}

5).Requirement: LEDs controlled by 3 switches. 4 LEDs and 3 switches connected in

PORTB. The user press the switch2 after pressing switch1 means LED will glow otherwise after

pressing switch3 means LED will off.

Coding:

// Program for controlling single LED by 3 switches

#define switch_1 PORTB.f0




#define LED PORTB.f4

#define ON 1

#define OFF 0

#define IO_config 0x0f

#define Port_config TRISB

#define Digital_port PORTB

#define clear 0

#define set 1

#define pressed 1

#define releassed 0

#define status_1 status.f0



void main()

{

unsigned char status,ABC=1,GHI=1;

status_1=clear;

status_2=clear;

status_3=clear;


Digital_port=clear;

Port_config=IO_config;

delay_ms(100);

while(1)

{

if(switch_1==pressed && status_1==clear)

{

status_1=set;

GHI=1;

}

if(switch_1==released && status_1==set)

{

ABC=0;

status_1=clear;

}

if(switch_2==pressed && status_2==clear )

{

if(ABC==0)

LED=ON;

if(GHI==0)

LED=OFF;


status_2=set;

}

if(switch_2==released && status_2= =set)

{

status_2=clear;

ABC=1;

}

if(switch_3==pressed && status_3= =clear)

{

status_3=set;

ABC=1;

}

if(switch_3==released && status_3= =set)

{

GHI=0;

status_1=clear;

}

}

}


6).Requirement: EEPROM handling. Store the value 150 in EEPROM.

Coding:

#define lcd_port PORTB

#define clear 0

#define set 1

unsigned char data=0;

void digit_disp(unsigned int digit,unsigned char row,unsigned char col,unsigned char count)

{

unsigned char temp;

if(count==3)

{

temp=digit/100;

digit=digit%100;

lcd_custom_chr(row,col,(temp+48));

col++;

}

temp=digit/10;

digit=digit%10;

lcd_custom_chr(row,col,(temp+48));

col++;

lcd_custom_chr(row,col,(digit+48));


}

void init()

{

lcd_port=clear;

lcd_custom_config(&PORTB,1,2,3,4,&PORTB,7,6,5 );

lcd_custom_cmd(lcd_clear);

lcd_custom_out(1,1,"WELCOME");

delay_ms(1000);


}

void EEPROM_handling()

{

soft_i2c_config(&PORTC,4,3);

soft_i2c_start();

soft_i2c_write(0xA0);

soft_i2c_write(7);

soft_i2c_write(150);

soft_i2c_stop();

delay_ms(2);

soft_i2c_start();



soft_i2c_write(7);

soft_i2c_start();


data=soft_i2c_read(0);

soft_i2c_stop();

}

void main()

{

init();

EEPROM_handling();


digit_disp(data,1,1,3);

}

5.7 EXERCISE PROGRAMS

1) Write a program to make 4 LEDs blink in alternative pins of PORTD.

2) Write a program to make running glow of LEDs in PORTA, PORTB, PORTC and

PORTD continuously.

3) Write a program to make the LED glow while pressing the switch1, off the LED while

pressing the switch2 and blink the LED while pressing switch3. PORT configuration is

your wish.

4) Write a program to blink 8 LEDs in both forward and reverse direction. The LEDs are

connected in PORTC.

5) Write a program to make LED glow after 5minites from switch pressed by using timer


interrupt.

6) Write a program to handling the menu using 4 switches. Switch1, switch2, switch3 and

switch4 are used as up arrow, down arrow, select and cancel button respectively.

7) Write a program to store the password in an array using keypad.

8) Write a program to write the password into the EEPROM.

9) Write a program to display “time out” when the user didn’t give the password for

5minites.

10) Write a program to compare the password given by user and the password stored in

EEPROM.

embedded notes.iet.trichy

Technology

embedded system hardware

components of embedded

view of embedded system

computer system

microprocessor system

system work

small scale embedded

irrigation system controller