I did something similar to a Sony CD head unit in my Mazda Protege. I us
ed
the existing steering wheel mounted cruise control buttons to control track
and volume functions on the headunit. Normally the buttons controlled the
normal cruise functions, but if both were pressed at the same time the
function would change. If left alone for more than 2 seconds the function went
back cruise. I too used a direct connection to the miniature snap dome
switches on the facepanel to a pin on a PIC16C54. I had the same problems
you're mentioning. Then I thought about it. The normal voltage on that side of
the switches is floating, not +5v. So instead of just setting the particular
pin after the button was released, I turn it into an input to tristate it.
After that change was made in the software, it worked wonderfully. Good luck.
Matt.


>To Anyone,
 >       After many hours of fingering over my code in search of a couple
>of bugs, I have finished a working version of an IR remote control
>decoder!  The only impediment in my path to complete success is a minute
>hardware problem.  I  am using a PIC16C84 to receive IR commands from a
>Kenwood remote.  If the PIC receives the correct command it will start,
>stop or pause a SONY portable CD player.  The CD player is the run of the
>mill portable player, which requires the user to depress a button to
>begin playing the CD, etc.  I want to use the remaining pins on the PIC
>to toggle these switches.  I tried to pull the terminal from the switch
>to ground using the PIC, but got no response.  I assume that there is too
>much internal resistance through the PIC's PORTB pins to ground for the
>switch to activate.  Might this be correct?  I thought about using a FET
>with teh gate connected to the PIC and the high side of the CD player's
>swithc connected to the source and the low side connected to drain
>(ground).  Does anyone have any alternative suggestions that are low
>power and low component number?