Known-good IBM joystick? (Evan Koblentz)

mike willegal mike at
Wed Jul 11 12:37:53 EDT 2018

A quick note on reading the Joystick ports on an Apple II.  The circuit uses a RC
timer to discharge a capacitor to measure the resistance of the potentiometer (resistor).
If you do multiple PDL reads back to  back, you may get a faulty reading the second
time.  This is because the capacitor needs time to recharge before the second read.
It's best to put some other code in between the paddle reads in order to give the capacitor
time to fully charge.

Mike Willegal

More information about the vcf-midatlantic mailing list