I have a small problem.
I'm using an external 32kHz XTAL to calibrate the internal 8Mhz oscillator to 7.3728MHz of an Atmega644P.
The method I use is from Application Note "AVR055: Using a 32kHz XTAL for run-time calibration of the internal RC".
But sometimes this calibration goes completely wrong. The cpu is working much faster (LED is blinking faster) and the serial connection is broken.
I have a bootloader which calibrates to 8MHz and cause we cannot change the bootloader in this project phase, I have to do the calibration for 7.3728MHz at the beginning of the program. But I have no idea why this happens.
I'm getting lost on this whole calibration thing.