Posted by Andy Warne on 14, 2000 at 2:43 PM:
In Reply to: Why not feed the circuit with +5 volts from the game-port if the serial-ports power supply is not enough (just a thought) *NT* posted by EmuMannen on 14, 2000 at 3:56 AM:
The happs trackball needs a solid +5V but it is not as simple as taking it from the PC because actually it has to be -5 volts (or +5V with the positive to ground) This is because serial mice work on a negative supply. There are various methods of getting around this such as using an opto-isolator for the link from the trackball to the interface to the serial port.
So there are two possibilities here:
1> replace the Happ optical board with one with no interface chip
2> design a new interface with isolated inputs but that will need +5Volts. This could come from the game port, ps/2 mouse port or I-PAC header plug.
Not made up my mind yet... Any thoughts welcome!