Programming in Embedded c

8/8/2019 Programming in Embedded c

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BY

LEENA AROZA

25-NOV-10

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C v/s Embedded C

Compile v/s Cross-Compiler

Programming in C

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C is a well structured, well defined and standardized general purposeprogramming language .

C offers a combination of the features of high level language andassembly and helps in hardware access programming (system levelprogramming) as well as business package developments (Applicationdevelopments like pay roll systems, banking applications etc)

ANSI standard language. Platform based Compiler.

EMBEDED C Subset of conventional C language C instructions and with few target processor specific functions/

Instructions.

Cross-compiler is used for the conversion of programs written inEmbedded C to target processor/controller specific instructions.eg:keil C51

The target processor/controller specific functions/instructions dependsupon the processor/controller

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C

C

Keywords &identifiers

Keywords &identifiers

Arithmeticoperations

Arithmeticoperations

Branchinginstructions

Branchinginstructions

Loopinstructions

Loopinstructions

Logicaloperations

Logicaloperations

Data types

Data types

Arrays &pointers

Arrays &pointers

Relationaloperations

Relationaloperations

Storage class

Storage class

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Primary Constants

Primary Constants

Array

PointerStructure

UnionEnum

Array

PointerStructure

UnionEnum

Secondary Constants

Secondary Constants

Integer ConstantsReal ConstantsCharacter Constants

Integer ConstantsReal ConstantsCharacter Constants

C

CONSTANTS

C

CONSTANTS


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Keywords

auto double int struct

break else long switch

case enum register typedef

char extern return union

const float short unsigned

continue for signed void

default goto sizeof volatile

do if static while

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Data Type Size (Bits) Range Comments

char 8 -128 to +127 Signed Character

signed char 8 -128 to +127 Signed Character

unsigned char 8 0 to +255 Unsigned Character

short int 8 -128 to +127 Signed short integer

signed short int 8 -128 to +127 Signed short integer

unsigned short int 8 0 to +255 Unsigned short integer

int 16 -32,768 to +32,767 Signed integer signed int 16 -32,768 to +32,767 Signed integer

unsigned int 16 0 to +65,535 Unsigned integer

long int 32 -2147,483,648 to

+2,147,483,647

Signed long integer

signed long int 32 -2147,483,648 to

+2,147,483,647

Signed long integer

unsigned long int 32 0 to +4,294,967,295 Unsigned long integer

float 32 3.4E-38 to 3.4E+38 Signed floating point

double 64 1.7E-308 to

1.7E+308

Signed floating point

(Double precision)

long double 80 3.4E-4932 to

3.4E+4932

Signed floating point

(Long Double

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Storage Class Meaning Comments

autoVariables declared inside afunction. Default storageclass is auto

Scope and accessibility is restricted withinthe function where the variable is declared.No initialization. Contains junk values at thetime of creation

registerVariables stored in the CPUregister of processor.

Reduces access time ofvariable

Same as auto in scope and access. Thedecision on whether a variable needs to be

kept in CPU register of the processordepends on the compiler

static Local variable with life timesame as that of theprogram

Retains the value throughout the program.By default initializes to zero on variablecreation. Accessibility depends on where thevariable is declared

externVariables accessible to allfunctions in a file and allfiles in a multiple fileprogram

Can be modified by any function within afile or across multiple files (variable needsto be exported by one file and imported byother files using the same)

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Arithmetic Operator Operation Comments

+ Addition Adds variables or numbers

- Subtraction Subtracts variables or numbers

* Multiplication Multiplies variables or numbers

/ Division Divides variables or numbers

% Remainder Finds the remainder of a division

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LOGICAL OPERATORSOperator Operation Comments

&& Logical ANDPerforms logical AND operation. Output is true(logic 1) if both operands (left to and right to of

&& operator) are true

|| Logical ORPerforms logical OR operation. Output is true(logic 1) if either operand (operands to left or

right of || operator) is true

! Logical NOT Performs logical Negation. Operand iscomplemented (logic 0 becomes 1 and vice

versa)

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//if statementif (expression){statement1;statement2;

.;}statement 3;..;

if else statementif (expression){

if_statement1;if_statement2;.;}else{else_statement1;else_statement2;.;}statement 3;

//if else statement

BRANCHING INSTRUCTIONS

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//switch case statementswitch (expression){

case value1:break;case value2:break;default:break;

}

Conditional operator// ?exp1 : exp2(expression) ?exp1: exp2

E.g.if (x>y)a=1;elsea=0;

can be written using conditionaloperator asa=(x>y)? 1:0

CONDITIONAL BRANCHING

INSTRUCTION

//unconditional branchingGoto label

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//while statement

while (expression){body of while loop

}

//do while loop

do{body of do loop}while (expression);

LOOPING INSTRUCTION

1) WHILE LOOP

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//exiting from loop

break;goto label

//for loop

for(initialization;condition;increment){body of for loop}

LOOPING INSTRUCTION

2) FOR LOOP

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Array is a collection of related elements (data types)Array declaration

data _type arr_name [num_of_arr_elements];

Eg: char arr[4];

0x200x20 0x300x30 0x400x40 0x500x50

0x9001 0x9002 0x9003 0x9004

arr[0] arr[1] arr[2] arr[3]

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ARRAY INITIALIZATIONS

//Initialization of array atthe time of declaration

unsigned char arr[5] = {5,10, 20, 3, 2};unsigned char arr[ ] = {5,10, 20, 3, 2};

//Selective initialization

unsigned char arr[5];

arr[0] = 5;arr[1] = 10;arr[2] = 20;arr[3] = 3;arr[4] = 2;

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Pointer is a memory pointing based technique for variable access andmodification.

Egg:

char input; =34 //Declaring input as character variable

char *p; //Declaring a character pointer p (* denotes p is a pointer)p = &input

MemoryaddressMemoryaddress

ContentContentVariable nameVariable name

inputinput0x340x34

0x70000x7000

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E.g. for the character array char arr[5], arr[ ] is equivalent to acharacter pointer pointing to the first element of array arr

The array features like accessing and modifying members of an array

can be achieved using a pointer and pointer increment/decrementoperators

Arrays and pointer declarations are interchangeable when they areused as parameters to functions

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Shibu K.V-Introduction to Embedded System

Yashavant Kanetkar-Let us C

Balaguru Swamy-programming in C

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Programming in Embedded c

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