[Coco] joystick plus real-time sound?

Charlie chazbeenhad at hotmail.com
Thu Jan 10 08:58:11 EST 2008

How can it be an "Arcade" game with no joystick control?
Sound is nice, no doubt, but a game is mostly about playing.
Thus a joystick would be the more important part.
Pulling off both the desired aound and aracde control would be the best of


"Roger Taylor" <operator at coco3.com> wrote in
message news:20080110011012.310287D114 at qs281.pair.com...
> At 06:23 PM 1/9/2008, you wrote:
> >Roger Taylor wrote:
> >
> >>Folks,
> >>If I'm not mistaken, there is no way on a CoCo to poll the joystick
> >>while doing real-time audio without introducing interference.  The
> >>same DAC is used to output the 6-bit sound and set the voltage for
> >>the joystick axis comparitors.
> >>When you set up the PIA to sample the joystick axis, I think a pop
> >>or click sound is introduced if the mode was in 6-bit sound
> >>mode.  Doing this frequently back and forth scares me with the thought.
> >>Ofcourse, on an emulator it probably doesn't do this.
> >>I could be wrong, but I think this is why I made my Spider-Hype
> >>games use only the keyboard.  I guess having real time music and
> >>sound effects has a cost.
> >
> >I think you can time share with careful coding. I remember doing
> >that in some software. I'll see if I can find the program source code.
> Remember that FIRQ is used for the audio pump.  It can occur at any
> time.  Any joystick sampling would probably have to be done
> "sometimes" during the FIRQ service code.  A cycling timer can be
> used but this will definately cause the game and framerate to appear
> to lag on intervals each time a polling is done, even with super fast
> code.  The existing FIRQ code is short and tight.  Adding 1 more
> instruction is noticeable in the audio and game speed.  Then the FIRQ
> timer has to be lowered a tad.  I had to fine-tune this over and over
> as the game progressed.
> Actually, there's a lot of IRQ and FIRQ servicing going on during the
> game.  IRQ sets up the MUSICA notes for FIRQ.
> I'd rather release the game as-is and supply any joystick version if
> I can pull it off.
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