[[File:Atari-ST mouse adapter.gif]]
The schematic was released in german 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
=== 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 (this could be fixed easily, by connecting the missing pin inside of the computer). 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.
== Timings ==
The Atari/Amiga mice do output low-level signals, directly coming from the motion sensors. Ideally, software should check the signals ''more than 500 times per second''. FutureOS does that, but not the firmware. Using the CPCs 300Hz interrupt to check the signals might be a bit slow; it would work, but may miss some signals when the mouse if is moved too fast.
Reading the mouse more often than 300 times per second would be better, but it'd require more CPU load since it can't be done via interrupts. Possibly best solution would be combination of IRQ and non-IRQ handling: Always check the mouse on 300Hz interrupts, and - if the program isn't busy with other tasks - additionally check it via polling.
== Software supporting the ST-Mouse ==
* [[G-Paint]] 2.0 (Günter Radestock)
* [[FutureOS]]
* [[G-Paint]] 2.0 (Günter Radestock)
[[Category:HardwareDIY]] [[Category:PeripheralsFutureOS]] [[Category:DIYInput Device]] [[Category:Peripherals]]