From: Hársfalvi Levente (hlpublic_at_freestart.hu)
Date: 2007-04-11 08:01:25
> > As of deciding which mode of operation should be the current one for
> > the interface (C64 vs. PXA270): instead of jumpers, you can probably
> > measure the supply voltage of the MCU right in the reset routine. All
> > those Atmels have a built-in voltage reference... measuring the supply
> > voltage by an ADC channel is fully possible. In the reset routine,
> > your code could decide if the unit is powered from 3.3 or 5v, and set
> > things up accordingly.
>
> Yes, very good point - I had thought of that, but was worried about
> accidentally sending 3.3V in to the C64! But I suppose it should be safe
> if nothing is sent out until this check is done - would also be handy to
> have the setup routine turn off the microcontroller's ADC Pot inputs in
> 3.3V mode, as they won't be needed...
After a power on reset, all pins of the AVR are in high-impedance state,
until your program decides otherwise.
Levente
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