A flexible open-source hardware expansion board for the EMF Tildagon badge supporting digital radio applications.
The hexpansion is based on the Semtech SX1278 radio module, controlled via SPI by a Raspberry Pi Pico, which in turn can get commands from or send data to the badge via the I2C and other I/O lines on the edge connector. There's also an EEPROM on board sharing the I2C bus, so the badge can check the hexpansion identifier and (if desired) boot your custom software.