Getting a trackball working

[njroadfan]

So I picked up this nice keyboard from a forum member:

So far probing around the inside hasn't been productive. The trackball properly detects and the buttons work when a mouse driver is loaded. Any input from the trackball itself is ignored. The infrared LEDs on the trackball sensors appear to work fine. The serial controller used is an Intel P8749H, likely with a custom programmed PROM. Could the problem be that chip, or one of the passive components on the board like a capacitor, resistor, etc? I'm hoping its something simple as its doubtful I can find parts for this unit or even another P8749H that hasn't been programmed already.

 

[Chuck(G)]

Have you tried the driver?

 

[njroadfan]

Have you tried the driver?

Yes, no dice, although the driver can switch the unit between MS mouse and Mouse Systems mode on the fly which is nifty. I found a serial mouse tester for windows: http://dmitrybrant.com/2000/07/13/serial-mouse-driver-tester

Forcing the trackball into MS mouse mode I did some debugging. Rolling the ball around generates no message packets over the serial port. I am getting packets when I press the buttons, so we can establish that no input from the optical sensors is making it to the computer. Grrr.

I also found out that the track ball circuit is powered from the keyboard port, not the serial port.

 

[Chuck(G)]

Well, it looks as if you need to see if the phototransistors are putting out any pulses. A logic probe might do the trick.

 

[njroadfan]

Now I have an excuse to buy one. This will have to wait until after vacation.