Cap-CC1101-SubG-Chat

Runtime-only Sub-GHz chat app for M5Stack CardputerZero and the Cap CC1101 accessory.

Features

• Send and receive messages over the verified 868 MHz low-rate 2-FSK profile (not LoRa)
• Show received signal strength and link-quality metadata
• Keep up to 64 messages in memory for the current session only
• Accept messages up to 61 printable ASCII bytes
• Use an SDL mock radio for desktop development without CC1101 hardware

Dependencies

Run the bootstrap script once after cloning this repository:

./bootstrap.sh

It fetches lvgl, spdlog, and smooth_ui_toolkit under dependencies/. SDL builds require SDL2 development files. CardputerZero builds additionally require libgpiod development headers and library.

Build

For SDL desktop testing:

cmake -S . -B build/sdl -DCC1101_CHAT_USE_SDL=ON
cmake --build build/sdl -j8

For a native CardputerZero build:

cmake -S . -B build/cp0 -DCC1101_CHAT_USE_SDL=OFF
cmake --build build/cp0 -j8

The output binary is dist/M5CardputerZero-Cap-CC1101-SubG-Chat.

Usage

Run the SDL build with:

CC1101_CHAT_SDL_ZOOM=2 ./dist/M5CardputerZero-Cap-CC1101-SubG-Chat

Key controls:

• Z/C or Left/Right: switch between Messages and CC1101 Info
• F/X or Up/Down: scroll messages
• Enter or a printable key: open the message editor
• Enter sends; Esc cancels or exits; Backspace/Delete and Left/Right edit
• R or Enter on the Info page: retry radio initialization after an error

Hardware

The device build uses the Cap CC1101 on /dev/spidev0.1 with kernel-managed CS1. Before radio initialization, the app checks the SPI node and, when needed, loads the BSP-provided /boot/firmware/overlays/spi0-spidev2-gpio22-overlay.dtbo. The overlay remains loaded until reboot.

The Debian package launches this hardware app as root through a non-interactive, command-specific sudo rule for members of the gpio group. The rule permits only the installed binary with no command arguments. This is currently needed for the Cap power controls exposed through the LED-class interface.

The current BSP may fail to apply the overlay at runtime. If initialization still reports a missing SPI node after loading, reboot once with dtoverlay=spi0-spidev2-gpio22-overlay in /boot/firmware/config.txt. Hardware initialization errors are shown on the Info page.

Package

Build the CardputerZero arm64 Debian package on an x86 Linux or WSL2 host with the Docker wrapper:

./packaging/docker/package_deb.sh

The wrapper downloads and caches the official CardputerZero BSP, cross-builds the device backend, and writes the package to dist/. To package natively on a CardputerZero instead, run:

./packaging/deb/package_deb.sh

The generated package is named:

dist/m5cardputerzero-cap-cc1101-subg-chat_<version>_m5stack1_arm64.deb