Re: Blink period shorter than expected

Are you compiling with -O1 or similar? I believe that some level of
optimization must be specified at compile time in order for _delay_ms() to
operate correctly. See
http://www.nongnu.org/avr-libc/user-manual/group__util__delay.html

-John


On Sun, Dec 1, 2013 at 11:41 AM, dfx <[email protected]> wrote:

> I made a very simple circuit for LED to blink.
>
> The code is as follows:
>
> # include <avr/io.h>
> # define F_CPU 20000000UL
> # include <util/delay.h>
>
> int main (void) {
> DDRB | = _BV (DDB0);
> while (1) {
> PORTB ^ = _BV (PB0);
> _delay_ms (10000);
> }
> }
>
> The processor is an ATMEGA324PA with clock = 20 MHz.
> The fuses are:
>
> lfuse = 0x4F
> hfuse = 0x99
> eFUSE = 0xFF.
>
> The problem is that the period of switching on / off of the LED is
> approximately 16 seconds. instead of 20 seconds expected.
>
> Where is the error? What should I check for a period of 20 seconds?
>
> Thank you to those who can help me.
>
> Domenico
>
> PS: I suppose that with a quartz 16 MHz operation would be correct, but
> there is a way to use one 20 Mhz?
>
>
>
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