I am trying to learn how to write programs to microcontroller, and started with very simple things like LED blinking with given frequency, or controlled by button. However, I have problems with using _delay_ms() from delay.h. As fas as I understood, for the correct work of this function, [optimization should be turned on][1]. When I write program to the microcontroller, instead of LED blinking, LED is constantly turned on with low brightness. When I tried just turn it on without delays, brightness is much higher, so looks like for some reason microcontroller gives some intermidiate low voltage, I am wondering why and what could be the problem. Below I describe what exactly I was doing. Code (main.c) looks like this (I am using attiny26, and asssume that it works at 1MHz).

#define F_CPU 1000000UL // 1 MHz clock speed
#include <avr/io.h>
#include <util/delay.h>
int main(void)
{
     DDRA |= (1<<PA0);  //A0 as output
     while(1) //infinite loop
     {
          PORTA |= (1<<PA0);// LED at A0 ON
          _delay_ms(1000); // 1 second delay
          PORTA &= ~(1<<PA0); //LED at A0 OFF
          _delay_ms(1000); // 1 second delay
          }
 }

I make object file with

avr-gcc -mmcu=attiny26 -O1 -c main.c

where -O1 is for level 1 of optimization. Then

avr-objcopy -O ihex main.o main.hex

and write to microcontroller:

sudo avrdude -c usbasp -p t26 -B 100 -U flash:w:main.hex:i

All the steps were completely without any errors or warnings. As I told above, resulting behaviour is weird: LED is constantly on with lith low brightness. Meanwhile, if I write to microcontroller program, where I just turn LED on (remove all the delays), LED will be turned on with full brightness. I was thinking if the optimization itself can be a problem, but in the regime without delays program works correctly in cany case - with optimization or without.

Controlling anything with button would require debouncing, and the same _delay_ms() function, which doesn't work for me. [1]: http://www.nongnu.org/avr-libc/user-manual/group__util__delay.html

I am trying to learn how to write programs to microcontroller, and started with very simple things like LED blinking with given frequency, or controlled by button. However, I have problems with using _delay_ms() from delay.h. As fas as I understood, for the correct work of this function, optimization should be turned on. When I write program to the microcontroller, instead of LED blinking, LED is constantly turned on with low brightness. When I tried just turn it on without delays, brightness is much higher, so looks like for some reason microcontroller gives some intermidiate low voltage, I am wondering why and what could be the problem. Below I describe what exactly I was doing. Code (main.c) looks like this (I am using attiny26, and asssume that it works at 1MHz).

#define F_CPU 1000000UL // 1 MHz clock speed
#include <avr/io.h>
#include <util/delay.h>
int main(void)
{
     DDRA |= (1<<PA0);  //A0 as output
     while(1) //infinite loop
     {
          PORTA |= (1<<PA0);// LED at A0 ON
          _delay_ms(1000); // 1 second delay
          PORTA &= ~(1<<PA0); //LED at A0 OFF
          _delay_ms(1000); // 1 second delay
          }
 }

I make object file with

avr-gcc -mmcu=attiny26 -O1 -c main.c

where -O1 is for level 1 of optimization. Then

avr-objcopy -O ihex main.o main.hex

and write to microcontroller:

sudo avrdude -c usbasp -p t26 -B 100 -U flash:w:main.hex:i

All the steps were completely without any errors or warnings. As I told above, resulting behaviour is weird: LED is constantly on with lith low brightness. Meanwhile, if I write to microcontroller program, where I just turn LED on (remove all the delays), LED will be turned on with full brightness. I was thinking if the optimization itself can be a problem, but in the regime without delays program works correctly in cany case - with optimization or without.

Controlling anything with button would require debouncing, and the same _delay_ms() function, which doesn't work for me.

UPD: Commenting out #define F_CPU 1000000UL or increasing argument of _delay_ms() doesn't help. But increasing delay time by making iteration for (i=0; i<100000; i++) {_delay_ms(1000);} leads to LED being constantly turned on with full brightness. Tested smaller times of iteration (10, 100, 1000, 10000) do not give full brightness of LED.