Re: Commodore joystick ports

From: Hársfalvi Levente (
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.


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