Turning led off after 30 seconds

avr

Hi I'm driving some leds using bs170 mosfet. The led's are lighting up however I would like to be able to turn it off after 30 seconds say. I tried using the following code but it didn't work. I think it's turning off and on faster than I notice. I seem to be getting a square wave on the scope on the pin that the fet is connected to.

/*
 * AVRGCC1.c
 * 
 * Created: 21/04/2011 21:38:56
 *  Author: steven
 */ 

#define F_CPU 20000000UL  // 1 MHz 

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

int main(void)
{ 
        //TODO:: Please write your application code 
        DDRA=0b00000001; //Make PDA0 as output  
        PORTA =0b00000001; // turn on fet  
        _delay_ms(30000);
        DDRA=0b00000000;
}

Best Answer

This part ..

PORTA =0b00000001; // turn on fet 
_delay_ms(30000);
DDRA=0b00000000;

should probably look like this ..

PORTA =0b00000001; // turn on fet 
_delay_ms(30000);
PORTA=0b00000000;

i.e., you don't want to redefine the direction of the pin, you want to change its state.

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