Atmega8 internal oscillator delay() function

Hi everyone,
I just bought a Atmega8 and burned the bootloader through the Arduino GUI. Now I try the Blink example to test if the new Atmega8 was working. I hooked the oscilloscope to pin 19 (LED_BUILTIN) and measure the time between high and low state. The time between High and low was 2000ms, not the 1000ms as I was expected. Is this a normal behavior, or it's a bad chip?

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Oh well I forgot that, I modified the low fuse bit in boards.txt to set the oscillator to 8mhz internal oscillator.

You've probably forgot to change the frequency in the boards.txt file. However, if you want a better solution for running the ATmega8 with different clock frequencies, you should install MiniCore. GitHub - MCUdude/MiniCore: Arduino hardware package for ATmega8, ATmega48, ATmega88, ATmega168, ATmega328 and ATmega328PB

by using MiniCore and the internal oscillator, you'll gain two more IO pins :wink:

I have tried install MiniCore, config the Atmega8 to run on 8Mhz internal oscillator, but when I use the command: delay(10); the result is still the same: a delay of 20ms instead of the expected 10ms. I tried 1Mhz internal oscillator and seem that the delay is now increased 8 more times (a delay of 160ms instead of the expected 10ms). If I use a external crystal at 16mhz, the delay command works fine. Everything works fine at 8mhz, except that delay(). Please explain this more clearly.

You need to re-burn the bootloader in order to set the correct fuses. Are you uploading using a programmer, or via a USB to serial adapter?

Thanks a lot, I forgot to use the correct .hex bootloader file. After using the one designed for 8hmz operation it work well now :slight_smile:
One more question please, the new XTAL1 and XTAL2 count as digital pin without pwm?