Software

The repository ships two firmware builds from the same hardware. They differ in the USB HID class they present, which is the only thing that decides where they work.

Choosing a target

Use pico_platformio_touch_mouse when:

• the host application expects a standard USB mouse
• relative movement is acceptable or preferred
• you want the simplest possible build environment, since PlatformIO handles the toolchain

Use pico_sdk_touch when:

• the host runs LVGL through the evdev or libinput backend and needs a real touchscreen device
• absolute coordinates are required, for a kiosk, an embedded HMI or a drawing tablet
• the HID descriptor needs full control

The two implementations

Signal processing

Resistive panels are electrically noisy, so the readings are cleaned before they reach the host. The Pico SDK digitizer build has the fuller pipeline:

1. 5-sample median filter, which removes single-sample spikes before anything else runs
2. exponential moving average, low-pass filtering the mapped coordinates to smooth motion while staying responsive
3. jitter suppression threshold, which suppresses HID reports when the smoothed position has not moved meaningfully, so a held contact does not tremble
4. release guard timer, which debounces PENIRQ on lift-off so a drag does not end early

The mouse build keeps a smaller filter, since a relative cursor tolerates more noise than an absolute digitizer does. See Signal filtering and USB HID descriptors.

Build commands

# PlatformIO mouse target
cd pico_platformio_touch_mouse && pio run --target upload

# Pico SDK digitizer target
cd ../pico_sdk_touch && mkdir -p build && cd build && cmake .. && make

Both targets read the calibration constants from their own source file, so a panel change means editing both.