Question

Answer the following question from the perspective of AVR (C language)

How to set the data direction (output/input) in (AVR, c language)?

Write a statement to turn ON a pin, say D3.

Write a statement to turn OFF a pin, say D3.

How to toggle a pin?

Answer 1

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Note :-

1. We are using Atmega32 avr micro controller .

2. LED connected on pin number 3 of PORTD please check image for hardware connection.

3. To blink led we have to make this pin Output .

Program Plan :

1. Define Header file of AVR.

2. Define Micro controller frequency .

3. Make output to the pin .

4. set high on pin to turn on led ,low for turn off led and for blinking for a period make it toggle

Program :

1. Set output the Pin -> set 1 in DATA Direction Register(DDRD) of PORTD

  DDRD|=(1<<3); //output the PORTD.3 pin   

D3 means PIN 4 of PORTD so to effect particular pin we are shifting lef by 1 for 4 number pin . using OR sign to not effect the other pin of PORT.

  

2. Set Input -> set 0 in DDRD of PORTD

DDRD&=~(1<<3) //input the PORTD.3 pin

it will set 0 the D3 pin using AND operation to do not effect other pin .

3. Turn on D3 pin of PORTD

PORTD|=(1<<3) //set 1 to turn on led

4. Turn of D3 pin of PORTD

PORTD&=~(1<<3) //set 0 to turn off led

5. toggle the D3 pin

PORTD^=(1<<3) //toggle the D3 means EX-OR of status of pin

it will EXOR the value of PORTD3 pin value .

Program :

this program will turn on and off the led for 1 second .

#ifndef F_CPU
#define F_CPU 16000000UL // 16 MHz clock speed
#endif

#include <avr/io.h> //avr header file
#include <util/delay.h>

int main(void)
{
DRRD|=(1<<3) //Output
  
while(1) //infinite loop
{
PORTD|=1<<3 //turn on led
_delay_ms(1000); //1 second delay
PORTD&=~1<<3 //turn off led
_delay_ms(1000); //1 second delay
     
}