Bluetooth MIDI Host - nRF52840

Connects to a BLE MIDI peripheral as a central, pairs with it, and forwards all incoming MIDI to both USB MIDI (class-compliant) and serial MIDI (DIN-5 / TRS via an optocoupler at 31250 baud).

Bonus: When no BLE peripheral is connected, the bridge instead acts as a bidirectional USB serial MIDI interface (USB in -> serial out, and serial in -> USB out). This USB/serial bridging is automatically disabled while BLE is connected, so it can't echo or interfere with the BLE MIDI stream.

Target board: SuperMini / ProMicro nRF52840 (Nice!Nano-compatible clone, $3 on aliexpress)

The same code also runs on the Seeed XIAO nRF52840, nice!nano v2, and Nordic DK with only the pin defines changed.

https://github.com/sneak-thief/BLE-MIDI-Host-nrf52840/