Difference between revisions of "Atari-ST mouse adapter"

Revision as of 23:06, 8 March 2010

This adapter allows to connect Atari ST mouse and trackball.

The schematic was released in german magazine "Schneider Magazin, 07/1988", apparently using 5 diodes and a 4.5V battery.

Aside from Atari-ST mice, the circuit should also work for Amiga mice, which are basically the same, but with XA/XB/YA/YB connected to other pins, which could be resolved at software side (or at hardware side).

 CPC Joy Port                     Atari-ST Mouse      Amiga Mouse
 JoyUp    Pin1 --|>|------------- Pin1 XB             Pin1 YA
 JoyDown  Pin2 --|>|------------- Pin2 XA             Pin2 XA
 JoyLeft  Pin3 --|>|------------- Pin3 YA             Pin3 YB
 JoyRight Pin4 --|>|------------- Pin4 YB             Pin4 XB
 JoyFire2 Pin6 ------------------ Pin6 Left Button    Pin6 Left Button
 JoyFire1 Pin7 ------------------ Pin9 Right Button   Pin9 Right Button
 JoyFire3 Pin5 --|>|------------- Pin8 GND            Pin8 GND
 JoySel1  Pin8 ------------------ Pin8 GND            Pin8 GND
 Batt4.5V (-)  ------------------ Pin8 GND            Pin8 GND
 Batt4.5V (+)  ------------------ Pin7 +5V            Pin7 +5V

The low-level XA/XB/YA/YB signal must be watched by software (the 300Hz interrupt is probably too slow to sense fast motions, so there's little chance to have the mouse driver running in background).

CPC Plus Compatibility

The circuit reportedly doesn't work on CPC Plus computers. Probably simply because of the missing Fire3 signal on the joystick port of the CPC Plus. There are also additional diodes in the CPC Plus, which may drop the voltages a little, but probably do not cause problems in this case.

Software supporting the ST-Mouse

• G-Paint 2.0 (Günter Radestock)
• FutureOS