retrolefty:
JoeN:
mauried:
The parallel resistor is in the AVR, you cant switch it out.
You dont need an external parallel resistor.Ah, you said "AVR" and I read "Arduino". My fault. The Arduino UNO R3 has an additional external parallel 1M resistor, that is the one I was talking about. It appears to be unnecessary in most circumstances, but doesn't cause any side-effects so appears to be a good design choice.
I question the accuracy of that schematic as the current arduino R3s seem to ship with a 16 MHz crystal for the 16u serial converter chip but utilize a 16 MHz ceramic resonator (with internal caps) for the 328p chip. I don't own a R3 but that's what has been reported by many.
Maybe it needs to be updated, but I got it from the most authoritative source I could find: