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[SOLVED] need help with AVR button

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anschau

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I am using Atmega8 for an led project. i wold like to use a button to tell the program to change between different light patterns with the leds. i think what i need to do is something like this

void main (){

DDRD = 0x00;
PORTD = 0xff;

while (1){

/* code for light pattern

if (PIND == 1){
return (1);
}else return (0);
}
}

can some one tell me what im doing wrong in this code or suggest a simpler easy to understand code.
 

I suppose that you know how the three port registers work, you can take a look at

Also check my post here https://www.edaboard.com/threads/166246/#post894717

In your code you enable the pullups so all the inputs will have the value of 1 unless they are grounded by a button.
Using the CHECKBIT define ( #define CHECKBIT(ADDRESS,BIT) (ADDRESS & (1<<BIT)) ) you can read the input using if (!CHECKBIT(PIND,x)) where x in the pin number (0 to 7) to detect when the input is grounder.
So for example if (!CHECKBIT(PIND,0)) will be true if PORTD bit 0 is grounded by the button.

Alex
 

i tried this but it did not work. can you tell me if there is a problem with the program? and can you also use your code in an example script?

#ifndef F_CPU
#define F_CPU 1000000UL
#endif
#include <util/delay.h>
#include <avr/io.h>
#define CHECKBIT(PIND,1) (PIND & (1<<1))
int main(void)
{
DDRB = 0xff;
DDRC = 0xff;
DDRD = 0b00000000;
while (1)
{

while (1) {
PORTC = 0b11101111;
PORTB = 0b00000001;
_delay_ms(200);
if (!CHECKBIT(PIND,1))
{
return (1);
}else return (1);
}
PORTC = 0b11111111;
PORTB = 0b00000000;
_delay_ms(10000);

}


return (0);
}
 

The define you have used is not correct, the define I have provided is #define CHECKBIT(ADDRESS,BIT) (ADDRESS & (1<<BIT)), you only use specific port and bit in your code later.

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#ifndef F_CPU
#define F_CPU 1000000UL
#endif
#include <util/delay.h>
#include <avr/io.h>
#define CHECKBIT(ADDRESS,BIT) (ADDRESS & (1<<BIT))
 
int main(void)
{
    DDRB = 0xff;
    DDRC = 0xff;
    DDRD = 0b00000000;
    PORTD =0b00000010;  // use the pullup in the pin with the button (bit1)
    while (1)
    {
 
        while (1) {              // you will never get out of this loop
            PORTC = 0b11101111;
            PORTB = 0b00000001;
            _delay_ms(200);
            if (!CHECKBIT(PIND,1))  // this will be true when pin1 is 0, the same as if (!(PIND & 0x02))
            {
              //  return (1); // don't use return, set a variable or execute some code 
            } else //return (1);
        }
        PORTC = 0b11111111;  // you will never execute this
        PORTB = 0b00000000;
        _delay_ms(10000);
 
    }
 
 
    return (0);
}


You also have to use the internal pullup (or external but there is no reason for that) so that the default state of PORTD pin1 is 1 and you can detect when it becomes 0 (when button is pressed).
Why do you use return inside main?
You shouldn't exit the main function in an embedded system , that is why you use the while loop, if you want a function that returns a result then call another custom function.
The main() function is the lowest level task, getting out of it will have unpredicted random results

Alex
 
Last edited:

okay thank you very much for your help. The example code helped a ton!
 

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