Erratic behaviour joystick button on soundblaster.

Hi everybody,

I just installed an old PC that has a sound card(isa with sound
card+joystick interface) that i use as an automation
device(programmed
in Pascal).
What it does is read for many hours the joystick port for buttons
pressed(a digital sensor connected to a relay closes the circuit and
generates the event).
The problem is that is generating erratic button presses( with
absolutely no aparent
reason - it works for days with no problem then it fails) - it might
be the sensor who sends the wrong signal..electric
contamination...but
i believe the problem is on the side of the computer.
What should i do - might it be a defective sound blaster compatible
card?

The sensor is trying to sense a metal(the metal is glued to a 35mm
cinema film)..when
it senses the metal(very rapidly..in a fraction of a second) it
activates a "relay" that closes
the circuit for the joystick button generating an event.


The code i use to read the bit In pascal:


FUNCTION button_1 : Byte;
BEGIN
button_1 := ((Port[$201] AND $10) XOr $10) ShR 4;
END;


Isn't there a way to force the event to last longer than the time
the relay is active to allow me to diferentiate between real events
and hipothetical electricity contamination?


Some sort of a timer..everything happens very quickly...


Thank You.




An help would be welcome.

On Aug 21, 1:25 pm, cyberfreak <AFSem...@gmail.com> wrote:
> The problem is that is generating erratic button presses( with
> absolutely no aparent
> reason - it works for days with no problem then it fails)

That could be anything, but it's not your code and I highly doubt it's
the sound blaster. It's either the PC getting hot and erratic, or
some operating system issue after being up for four days.

> Isn't there a way to force the event to last longer than the time
> the relay is active to allow me to diferentiate between real events
> and hipothetical electricity contamination?

Sure, using a loop while looking at the 8253/4 timer to figure out how
long things are taking. Look up PCTIM003.TXT for everything you ever
wanted to know about using the timer.