WorkerMouse

About

The WorkerMouse was a project I did as an exercise in learning about USB and HID devices. It is a Mouse Jiggler that pretends to be a legitimate USB device.

Hardware

I began with an ESP32-S2 but quickly realized it was overkill for creating a simple mouse. I’m very familiar with the ATtiny85, but it doesn’t have a hardware USB peripheral. Luckily, I was able to stand on the shoulders of giants — the V-USB project was built to run on AVR MCUs. This software-only USB implementation allows the ATtiny85 to act as a low-speed USB 1.1 device, which is perfectly adequate for a HID mouse.

The V-USB site is also a treasure trove of information for building simple USB devices. It includes dozens of reference projects with both hardware and software documentation. The HIDKeys example was a perfect reference for the hardware side of this project, especially when combined with the Hardware section of their overview page.

Software

The software is open source and available at github.com/zbauman3/WorkerMouse.

With the hardware design and USB driver settled, all I needed to do was write some software to periodically move the mouse. I chose to write it using the AVR Toolchain (v3.7.0), which relies on the excellent avr-libc (v2.0.0). I took this approach as an exploration into using the toolchain developed by the hardware manufacturer, rather than a third-party abstraction like Arduino.

I wanted the mouse movements to feel somewhat realistic — mostly just for fun. This meant the only software I needed to write was a timer to periodically move the mouse, use a pseudo-random number generator to pick movement amounts and speeds, and a USB report generator. Altogether, that’s less than 200 lines of code (not including the USB device configuration such as name, VID/PID, etc).

Once the project was complete, I decided to explore officially registering the USB device. Since I didn’t want to pay the $6,000 required by the USB-IF to acquire my own Vendor ID, I went with pid.codes. They own the Vendor ID 1209 and allow any open-source project to register a Product ID under it. I registered the WorkerMouse as VID 1209, PID F480.

All in, the software ended up being 2636 bytes of ROM and 89 bytes of RAM.

Media

Parts List

• 1 ATTINY85 20PU
• 1 16MHz Crystal
  • 2 20pF capacitors
• 1 USB-C receptacle
• 2 1N5227B - Zener Diodes 3.6V 0.5W
• 1 10µF Capacitor
• 1 0.1µF Capacitor
• 2 47-Ohm Resistors
• 1 2.2K-Ohm Resistor
• 1 5.1K-Ohm Resistor

Downloads

3D Models

I used PETG for the case, and separate colors for the lettering / case. This was the video I followed for using two colors with one toolhead: https://www.youtube.com/watch?v=zk1vKVphE1M.

If you'd rather not use two colors, you can simply omit the letter models and the letters will be debossed.

• Zip file with all models

Compiled Firmware

The compiled firmware can be downloaded from the Github repo at /firmware/compiled.