You can get the code for this project here.

Adapted from a project by GuilleAcoustic and Johan Berglund. Using USB code by Darran Hunt, Anh Nguyen .

I adapted the GuilleAcoustic and Johan Berglund code to run on an Arduino UNO, instead of the Sparkfun Pro Micro. This was purely because I only had an UNO. This meant that another method of USB communication needed to be found, as the UNO does not support the library calls used in the orignal code. I found a solution by Darran Hunt in a good tutorial by Anh Nguyen, and updated the code with that.

Note that it requires the UNO firmware to be changed while running the application.

The other significant change was to move to a polling method for the rotary encoders from the mouse, as the UNO only has 2 interrupt pins, where 4 are required for both axes. I thought this would severely affect the usability of the mouse, but it works quite well.

Wiring

Connection to M0100 DB9: (M0100 info from https://support.apple.com/kb/TA29935)

M0100 DB9	Arduino UNO
1 GND	GND
2 VCC	VCC
3 GND	GND
4 X2 Horizontal movement line	PIN4
5 X1 Horizontal movement line	PIN5
6 Not used	-
7 SW- Mouse button line	PIN7
8 Y2 Vertical movement line	PIN8
9 Y1 Vertical movement line	PIN9

Using the software

The software requires changing the Arduino firmware, using a DFU (Device Firmware Update) programmer. Follow the instructions here (https://www.arduino.cc/en/Hacking/DFUProgramming8U2) to get the right DFU programmer for your system

The procedure to use the mouse driver code is then as follows:

1. Upload the sketch in the src folder in the repo to the Arduino UNO using the normal IDE
2. Power cycle the Arduino UNO
3. Reset the 16u2 chip by shorting the reset pins
4. Upload the Arduino-mouse-0.1.hex file using your DFU programmer. If you are using macOS, you can use the shell script hid-mode.sh to upload the new firmware.
5. Power cycle the Arduino UNO again. The sketch should be running, and the Arduino will appear as a mouse to your system, and translate the movement from the M0100 mouse.

The procedure to revert to standard Arduino firmware (so that you can re-program etc) is as follows:

1. Reset the 16u2 chip by shorting the reset pins
2. Upload the file Arduino-usbserial-uno.hex using your DFU programmer. If you are using macOS, you can use the shell script prog-mode.sh to upload the firmware.
3. Power cycle the Arduino UNO. You will now be able to access it as usual.