# Jog wheel board

This board holds 24 keys and 5 LEDs.

The keys on this board are far from as orderly laid out as on the function board, so mapping them is also rather more messy.

Arbitrarily numbering things:

• key switches (red frame in above image):
  • pin 1 is connected across various keys
  • pin 2 is connected across various keys
  • pin 3+4 are shorted to pin 2 when the switch is pressed
  • between pins 1 and 2, there is a diode within the switch casing
• lighted key switches (yellow frame in above image):
  • pin 1 is connected across various keys
  • pin 2 is connected across various keys
  • pin 3 is negative terminal for LED
  • in this case, the pin 1 diode is external to the switch casing

Surprise: this board uses the same demultiplexer select lines (23, 25, and 27) as the function board. Perhaps other G1/G2 settings, then? Yes: G1 is pulled high and G2B is pulled low as above, but G2A is routed to its own ribbon line  (19), and should be pulled low when scanning.

As before, pin 1 on the key switches are run directly to the ribbon cable, and pin 2 on the key switches are run through a demultiplexer. Also as before, the demultiplier outputs and the return lines are active LOW, so all except the signalled line(s) will be set HIGH.

Demultiplexer

So it would seem that, to scan this board, I need to run a binary sequence 0-2 through ribbon lines 23, 25, and 27 to power the jog board keys (pin 2) as follows:

Any pressed key switches (pin 1) should then be signalled on (odd-numbered) ribbon lines 1-15:

Additionally, 5 of the keys have LEDs; these are all supplied with the same 5V from ribbon line 6/8/10 and individually lighted by pulling pin 3 down via separate ribbon lines.

So in short, here is my new knowledge about the ribbon cable: