Setting external oscillator for atmega328p

Question

I'm trying to use a 8MHz Oscillator on an atmega328p. this a part of the whole schematic :

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to that I've set the Fuse byte as calculated enter image description here[2]

then I've set the calculate values in the project :

enter image description here

To make sure that the uc ist correctly runnion on 8MHz, since I don't have an oscilloscope, I'm trying to toggle a LED each 1 sec, here is the code I've wrote for that :

#define F_CPU 8000000
#include <avr/io.h>
#include <util/delay.h>
int main(void)
{
DDRD |= (1 << PD5); 
 while(1){
 PORTD |= (1 << PD5); 
 _delay_ms(1000); 
 PORTD &= ~(1 << PD5);
 _delay_ms(1000); 
 }
 return 0;
 }

As far as I can see the lED take 8sec to change its status ! when I change the value of F_CPU to 1MHz the toggle is than correct, which means to me that I'm still running the internal oscillator ?

Any idea what I'm missing here ? thanks in advance !

Answer 1

You checked the divided by 8 fuse bit. So the CPU runs at 8mhz/8. Uncheck it.

• user98663: The devil is in the details. I've often wished for a "fuses wizard" in the Atmel Studio software that appears when starting a new project, one that asks some simple questions about the engineer's intentions and suggests a set of fuses that fit the task. It would be so helpful for those of us less familiar with the platform.