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Firmware (RPi Pico)

TinyGo firmware for a Raspberry Pi Pico. A physical button (short / double / long press) is reported to the host over USB HID as consumer reports.

What it does

  • Button (GPIO 14): Detects short, double, and long press; sends one HID consumer report per completed press.
  • LED (GPIO 15): Blinks by default. When the host sends the “LED on” byte on the keyboard report (report ID 2), the LED stays on as commanded, signaling the host software is running.
  • USB HID: Uses TinyGo’s CDC+HID composite. Consumer report ID 3 carries the 16‑bit press type; keyboard report ID 2 is used for host→device LED control.

File structure

  • main.go — Entry point: init, wait for USB, then a single loop that polls host reports, LED blink, and button; dispatches host bytes to handleHostReport and sends consumer reports on button events.
  • internal/button — Button on GPIO 14, debounce and state machine; Init() and Poll() return the press type (short/double/long) when a press is complete.
  • internal/led — LED on GPIO 15: Init(), On(), Off(), BlinkOn(), ShouldBlink() / BlinkLED() for the default blink and host-driven solid state.
  • internal/hid — HID device wrapper: Init(), SendConsumerReport(), Flush(), GetReceivedReport() for host output (e.g. keyboard report with LED byte). Uses the shared protocol package for report IDs and constants.

Flow

  1. main() initializes button, LED (starts blinking), and HID, then waits for USB ready.
  2. Main loop (every ~2 ms):
    • Read any host report via GetReceivedReport(); if keyboard report with LED byte, call handleHostReport() (switch LED to solid on/off or blink).
    • If led.ShouldBlink() is true, call led.BlinkLED() to toggle the LED.
    • Call button.Poll(); on completed press, send the corresponding consumer report and Flush().
  3. No goroutines; one non-blocking loop so USB and button are both serviced.

View logs

To view the RPi logs, find the USB device (ls /dev/cu.usb*) and connect to the console via the screen command.

For instance,

screen /dev/cu.usbmodem2101 115200