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MCUdude / MiniCore

Arduino hardware package for ATmega8, ATmega48, ATmega88, ATmega168, ATmega328 and ATmega328PB
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Clock options for ATMega328P are ambiguous #287

Closed Rob190 closed 6 months ago

Rob190 commented 7 months ago

For example if I select 'External 8Mhz', the documentation says "8MHz External crystal/oscillator | Common clock when working with 3.3V" but according to the datasheet this could mean:

  1. Full Swing Crystal Oscillator
  2. Low Power Crystal Oscillator 8.0 - 16.0 MHz
  3. External clock

These are distinct configurations so which one applies?

MCUdude commented 7 months ago

The fuses selects the full swing oscillator option. This is by far the most forgiving one, and are able to drive pretty much every crystal+capacitor(s) combination. The ATmega328PB does not have a full swing oscillator option, and is much, much more flakey when it comes to the oscillator circuity.