[...]Maybe not so unpredictable. Isn't a higher then Vcc voltage to the reset pin the method that puts the chip into it's high voltage programming mode? As I understand it the reset pin does not have an internal positive clamping diode to Vcc (unlike the normal I/O pins, just because of the higher then Vcc on reset method to enter HV programming mode.[...]Lefty
Would this then prevent the arduino board from being able to be programmed via the 'high voltage' method? Granted that would represent a very small population of users, however I've seen at least one shield based high voltage programmer avalible for sale. It allows those that have managed to 'brick' their processor by errors in fuse settings, i.e. change reset pin to be a I/O pin, etc.
If it does, it's easy for new design to add two via around the diode to shunt it easily using a basic wire, or even add an open pad to be shunt with solder.
QuoteIf it does, it's easy for new design to add two via around the diode to shunt it easily using a basic wire, or even add an open pad to be shunt with solder.But wouldn't that also shunt out the reset's pull-up resistor to Vcc, which would then cause direct connection from Vcc to the high voltage pulse/level used in HV parallel programming mode?Lefty