c programming language - german university in cairo

C Programming Language

Advantages over assembly language for microcontrollers:

More portable

Math functions

Readability

Maintainability

Editing C

End-of-line ignored

Use line breaks/tabs/indent for readability

Lines end in semicolon ;

Use Braces {} to group things

Comments: your code must have comments!

Standard C comment between /* and */ (no nesting)

C++ style common too, between // and end of line

Pre-Processor Performs text replacement before compile

Commands marked with “#” the “pound”

#include inserts entire file#include <stdio.h> // compiler library

#include “yourfile.h” //paste your file right here

.h files are header files Common declarations

Port, register names defined for chip (PORTB)

#define does search and replace#define this that // replace every “this” with “that”

#define MAX 100 // common for defining constants

Variables Names for memory locations

int: 16 bit

float: floating point (3.14)

char: 8 bit

unsigned char: 0-255

signed char: -128 to 127

long int or long: 32 bit

mikroC variable types

Logical Operators

x =10x > 8 // returns 1x ==10 // returns 1x < 100 // returns 1x > 20 // returns 0x != 10 // returns 0x >= 10 // returns 1x <=10 // returns 1

Logical Operatorsx = 7;x > 0 && x < 10 // returns 1x > 0 || x < 10 // returns 1x >=0 && x <=10 // returns 1x >=0 && x < 5 // returns 0a = 10; b = 20; c = 30; d = 40;a > b && c > d // returns 0b > a && d > c // returns 1a > b || d > c // returns 1

Bitwise Operators0xFA & 0xEE returns 0xEA0xFA: 1111 10100xEE: 1110 1110

0xEA: 1110 1010

0x01 | 0xFE returns 0xFF0x08: 0000 00010xFE: 1111 1110

0xFE: 1111 1111

0xAA ∧ 0x1F returns 0xB50xAA: 1010 10100x1F: 0001 1111

0xB5: 1011 0101

0xAA returns 0x550xAA: 1010 10100x55:

0x55: 0101 0101

0x14 >> 2 returns 0x05 (shift 0x14 right by 2 digits)0x14: 0001 0100>>2: 0000

0x05: 0000 0101

Data Accessing

/* Input/Output Ports initialization */

// Port A initialization

Accessing Registers

TRISA=0x01; // Initialize direction

TRISB=0b10110001;

PORTA=0x00; // Initialize state

Accessing Individual Bits

INTCON.GIE = 0; // Clear Global Interrupt Bit (GIE)

//GIE is defined in the definition file

INTCON.B0 = 0; // Clear bit 0 in INTCON register

INTCON.F5 = 1; // Set bit 0 in INTCON register

Accessing Individual Bits You can declare a sbit variable in a unit in such way that it

points to a specific bit in SFR register:

sbit Abit at PORTB.B0; // this is where Abit is fully defined

void main(){

Abit=1;

}

The mikroC compiler provides a bit data type that may be used for variable declarations. It can not be used for argument lists, and function-return values

bit bf; // bit variable

Arraysunsigned int Total[5];

Total[1] = 25;

unsigned char months[ ] ={31,28,31,30,31,30,31,31,30,31,30,31};

unsigned char Hex_Letters[ ] = {‘A’, ‘B’, ‘C’, ‘D’, ‘E’, ‘F’};

unsigned char Mystring[ ]=“COMP”;

unsigned char Mystring[ ] = {‘C’, ‘O’, ‘M’, ‘P’, ‘\0’};

unsigned char Q[2][2] = { {1,0}, {0,1} };

Variable declarations Local variables

Declared inside a function

Names can be reused

Not shared with other functions

Global variables

Declared outside functions

All functions can see and use them

Programming style determines use

Math Operators Main reason to use C over assembly

Standard arithmetic: + - * /

Modulus % gives remainder: 7 % 2 = 1

++ and -- increment and decrement

x++; // same as x = x + 1

+= is a shortcut (-=, *=, /= etc work too)

x+=2; // same as x = x + 2

Branches and Loopsif (x > y) {

x = 1; // if true

} else {

x = 34; // if false

}

for (count=0; count<7; count++)

{

// count is 0 through 6

x = x + count; // calculated 7 times }

MechatronicsEngr 415 Spring 2007

Branches and Loops continuedwhile (x > y) {

x = 1; // infinite loop?

}

switch (numx) {

case 1: // this happens if x = 1

y = y+x;

break;

case 3: // if x is 3 this executes

y = 23;

break;

default: // otherwise this happens

y = 0;

break;

}

MechatronicsEngr 415 Sprig 2007

Pointers and Arrays Pointers: variable location rather than value

Not used much in small microcontrollersint x; // regular int

int *p; // pointer to int

p = &x; // p has address of x

x = *p; // x has value pointed to by p

Arrays: vector of variables, index in []int i, pwm_out[8]; // 8 ints

for (i=0;i<8;i++) {

pwm_out[i]=0; // clear array

}

MechatronicsEngr 415 Spring 2007

Functions: Return a number or VOID #include <math.h> // need sin

float sx, x; // declare variables (global)

int z, z2;

// Function square starts here

int square(int x)

// custom user-written function to do square of 2 numbers

{

int y; // local variable

y = x*x; // function calculation

return y; // send this back

}

// Function main starts here

void main(void)

// there is always a main function

{

x =1.57; // radians

sx = sin(x); // function call

z = 2; // units?

z2 = square(z); // function call

}

Write assembly in C codeasm

{

Assembly language instructions ...

}