gastric wrote:* Firmware clock has to match the crystal clock.
* The ATmega32 16-PU is rated by the manufacturer for a clock for 16Mhz.
* Ideally, this would use a 16Mhz crystal to ensure a proper clock match. Use megadrum32_16_20081020 for firmware.
* However, you can PROBABLYuse a 20Mhz crystal which overclocks the 16Mhz ATmega to 20Mhz. Use megadrum32_20_20081020 for firmware.
* The ATmega644 20-PU is rated by the manufacturer for a clock of 20Mhz.
* Ideally this would use a 20Mhz crystal. Use megadrum32_20_20081020 for firmware.
* Assuming the above is true I'm assuming you could use a 16Mhz crystal and underclock the ATmega644 20-PU. Use megadrum32_16_20081020 for firmware.
All is right.
gastric wrote:Synthex, I'm not criticizing I'm just asking for my own education. Why not just specify for your users to use a 16Mhz crystal with the ATmega32 16-PU? It would seem to eliminates one potential problem with the build. Or if underclocking isn't an issue why not specify the 16Mhz crystal and be on the safe side for all builds?
Because the 20MHz version is more reactive.
And I've never had problem with overclocked Atmega.