USB Button (RPi Pico)

Firmware for a Raspberry Pi Pico with a physical button: short / double / long press are sent to the host as raw HID reports (consumer report ID 3 with a 16-bit event code). An LED on GPIO 15 blinks until the host signals ready, then follows host commands. You can customize the report payload and, with a TinyGo override, VID/PID and report format.

The repo is split into firmware/ (TinyGo, for the Pico) and host/ (regular Go, for the listener on your computer).

Quick start

• Hardware: Button on GPIO 14, LED on GPIO 15 (see firmware/internal/button and firmware/internal/led).
• Build & flash firmware:
  make build-fw && make flash
• Host: Build and run the listener (standard Go, not TinyGo):
  • make build-host then ./.bin/hid_listener
  • Use -list to list HID devices. Reports are 3 bytes: [0x03, event_lo, event_hi].

Documentation

• docs/HID_PROTOCOL.md – Explains the HID protocol: enumeration, report descriptor, and what the code does.
• docs/TINYGO_DEFAULTS.md – Explains what part of the the USB HID communication is handled by TinyGo for us
• host/README.md - Describes the host code in more detail
• firmware/README.md - Describes the firmware code in more detail

Troubleshooting

macOS: "Failed to connect to the device" (HID open failed)

1. System Settings → Privacy & Security → Input Monitoring
   Add Terminal (or Cursor / your IDE), enable it, then quit and reopen the app.
2. If it still fails, run the listener with sudo (macOS sometimes requires root for HID):
   sudo ./.bin/hid_listener
3. Unplug the Pico, plug it back in, then run again.