# BLE MIDI

Bluetooth Low Energy MIDI interface setup.

Build with `CS_MIDI_HID_KEYBOARD=ON` to also advertise as a BLE HID
keyboard with a Battery Service. This serves two purposes:

1. **Auto-reconnect** — the host OS auto-reconnects to bonded HID
   peripherals on power-up, which brings up the MIDI service without
   manual intervention.
2. **Battery level** — the standard BLE Battery Service (UUID 0x180F)
   reports charge level to the OS. Call `setBLEBatteryLevel(percent)` from
   your application to update it (e.g. from an ADC reading on a voltage
   divider).

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

```cpp pico
#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}};
CCRotaryEncoder enc {{0, 2}, {16, Channel_1}, 1, 4};

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