Re: Commodore joystick ports

From: Jim Brain (
Date: 2007-04-12 19:25:00

Daniel O'Shea wrote:
> Jim, how possible do you think it is that your existing code could 
> also be adapted to the VIC-20 or Atari paddle inputs? I'm not exactly 
> sure how their timing works, but I do know that they use 1000pF 
> capacitors, and 1M rather than 500K potentiometers... would it be as 
> simple as listening for the interval between IRQs to know which system 
> is connected?
VIC-20 should be pretty easy, since I believe the SID POT stuff was 
probably lifted from the VIA circuits.  The 2600 looks to operate on the 
same principle, but the timebase looks different (measuring the time in 
the links you sent implies a slower charge time, since a SW check would 
take more time.  On the plus side, it's easy to make the code runn slower. 

For the code to operate, you'd have to know the min/max time period.

I thought I had a 2600 around, but I think it got trashed long ago.


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