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MIDI over BLE

Original: MIDI over BLE

BLE MIDI uses BTstack to advertise a standard MIDI BLE service. Compatible with macOS, iOS, Windows 10+, and Android.

Backend

cs-midi uses the BTstackBackgroundBackend, which runs BLE asynchronously but requires periodic update() calls for outgoing message buffering.

The convenience typedef:

using BluetoothMIDI_Interface = GenericBLEMIDI_Interface<BTstackBackgroundBackend>;

Basic usage

#include "pico/stdlib.h"
#include "pico/cyw43_arch.h"
#include <cs_midi.h>

using namespace cs;

BluetoothMIDI_Interface midi;

NoteButton button {5, {MIDI_Notes::C[4], Channel_1}};

int main() {
    stdio_init_all();
    if (cyw43_arch_init()) return 1;
    Control_Surface.begin();
    while (true) {
        Control_Surface.loop();
        sleep_ms(1);
    }
}

cyw43_arch_init() is required to bring up the radio before BLE operations.

HID keyboard + Battery Service

Build with CS_MIDI_HID_KEYBOARD=ON to advertise as a BLE HID keyboard alongside MIDI:

Auto-reconnect — the host OS auto-reconnects to bonded HID peripherals on power-up, bringing up the MIDI service without manual intervention.
Battery level — the standard Battery Service (UUID 0x180F) reports charge level. Update with:

setBLEBatteryLevel(percent);

No keyboard input is sent — the HID descriptor exists solely to trigger OS auto-connect behavior and surface the battery indicator.

Radio module

The BLE transport requires a CYW43 radio. Only the Infineon RM2 module has been tested. A board file for the Waveshare RP2350B Plus W (RM2-equipped) is provided at boards/waveshare_rp2350b_plus_w.h.

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