This code lets you connect a Depraz mouse (or a classic Macintosh DB9 mouse) to a modern computer via USB. The Depraz mouse has a male DE-9 connector but does not use RS-232. Instead, it directly exposes the internal quadrature encoders (two pins for X axis, two pins for Y axis) and each of the three buttons gets its own pin. Add in +5V and GND pins and you've got 9 wires.
You'll need a board with an ATmega32U4 in order to emulate a USB HID device. I used an Arduino Pro Micro with 1M pullup resistors connected to pins 7, 8, and 9. To break out the DB9 port, I used https://www.amazon.com/gp/product/B07PNWF3DW/.
For the Depraz, I connected it as follows:
| Mouse port pin | Arduino pin |
|---|---|
| 1 (+5V) | Vcc |
| 2 (Y1) | 0 |
| 3 (Y2) | 1 |
| 4 (X1) | 2 |
| 5 (X2) | 3 |
| 6 (GND) | GND |
| 7 (mid button) | 7 |
| 8 (right button) | 8 |
| 9 (left button) | 9 |
It also works with an original Macintosh mouse if wired as follows:
| Mouse port pin | Arduino pin |
|---|---|
| 1 (GND) | GND |
| 2 (+5V) | Vcc |
| 3 (GND) | GND |
| 4 (X2) | 3 |
| 5 (X1) | 2 |
| 6 (NC) | (not connected) |
| 7 (button) | 9 |
| 8 (Y2) | 1 |
| 9 (Y1) | 0 |
If you find the pointer moves way too fast/slow for you, tweak the SPEED_CONSTANT define at the top of the file.
If your vertical movement is inverted, swap Arduino pins 0 and 1. If horizontal is inverted, swap 2 and 3.
When I plugged it into an old Powerbook running Mac OS 9, the OS didn't recognize it as a mouse.
This has only been tested with a red "Type D 83/P" mouse. Apparently the grey ones have a different pinout on the connector:
- 1 - GND
- 2 - MB
- 3 - Y
- 4 - LB
- 5 - RB
- 6 - Vcc
- 7 - Y
- 8 - X
- 9 - X