Paja

Bit operations are used when interfacing with digital out such as switching pins On/Off. Programming with bit operations enable  following functions to control digital out.

• Switching pins on (for example, turning on LED)
• Switching pins off (for example, turning off LED)
• Toggling pins (for example, Turning of LED if it is on and vice versa)

Bit operations:   &, |, ^, >>, <<, ~

& – bitwise AND

DDRB = 0b11110000;

DDRB &= 0b00010000;

-> DDRB = 00010000

| – bitwise Inclusive OR (Switch on bit)

DDRB = 0b00000000;

DDRB  |= 0b00010000;

-> DDRB = 00010000

Example a:

PORTB |= (1<<PB5);     //Put Port B bit 5 HIGH

Example b:

PORTB = (1<<PB2)|(1<<PB5);     //Put Port B bit 2 and 5 HIGH

– >

00000000

AND

00000100

OR

00100000

=

00100100

^ – bitwise Inclusive OR (Toggle bits on/off)

DDRB = 0b0001001;

DDRB ^= ob00010000;

-> DDRB = 00000001

Example:

PORTD ^= (1<<PD6);     // Toggle PortD bit 6

<< – Left shift

DDRB = ob10000000;

DDRB |= (1<<5);

-> DDRB = 10010000

~ – One’s complement (Switch off bits)

DDRB = 0b11111111;

DDRB &= ~(1<<5);

-> DDRB = 11101111

Example:

PORTD &= ~(1<<PD5);     // Put PortD bit 5 LOW

This code is for excersizing bit operations to manage digital output.

main.c

// Title: Experiencing switching and toggle pins on/off

// Description:

// Each Arduino pin 5, 6 and 7 pin is connected to a LED.

// This code is for excersizing bit operations to manage digital output.

// AVR-GCC uses bit operations heavily to interface I/O.

// Atmega8 PortD bit | Arduino pin

// 5                 | 5

// 6                 | 6

// 7                 | 7

#include <avr/io.h>

#include <util/delay.h>

void delay(int);

int main(void){

// put PortD bit 5, 6 and 7 as output

DDRD = (1<<PD5)|(1<<PD6)|(1<<PD7);

for(;;){

//***** Exercising HIGH and LOW

PORTD |= (1<<PD5);     // Put PortD bit 5 HIGH

delay(1000);

PORTD = PORTD | (1<<PD6) | (1<<PD7);     // Put PortD bit 6 and 7 HIGH

delay(1000);

PORTD &= ~(1<<PD5);     // Put PortD bit 5 LOW

delay(1000);

PORTD = PORTD & ~(1<<PD6) & ~(1<<PD7);     // Put PortD bit 6 and 7 LOW

delay(3000);

//***** Exercising TOGGLE

PORTD ^= (1<<PD6); // Toggle PortD bit 6

delay(1000);

PORTD = PORTD ^ (1<<PD5) ^ (1<<PD7); // Toggle PortD bit 5 and 7

delay(1000);

PORTD = PORTD ^ (1<<PD5) ^ (1<<PD6) ^ (1<<PD7); // Toggle PortD bit 5, 6 and 7

delay(5000);

// Result shows following LED flow

// Aruduion pin | 5 | 6 | 7

//              |   |   |     Exercise HIGH and LOW

//              | * |   |

//              | * | * | *

//              |   | * | *

//              |   |   |     Exercise TOGGLE

//              |   | * |

//              | * | * | *

//              |   |   |

}

return 0;

}

void delay(int ms) {

ms /= 100;

char i;

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

_delay_ms(100);      // max is 262.14 ms / F_CPU in MHz

}

}