# Receiving MIDI Messages

> Original: [Receiving MIDI messages](https://tttapa.github.io/Control-Surface/Doxygen/d3/df7/midi-tutorial.html)

## With MIDI_Callbacks

Register a callback object on the interface to handle incoming messages:

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

using namespace cs;

BluetoothMIDI_Interface midi;

struct MyCallbacks : MIDI_Callbacks {
    void onChannelMessage(MIDI_Interface &, ChannelMessage msg) override {
        auto type = msg.getMessageType();
        Channel ch = msg.getChannel();
        uint8_t d1 = msg.getData1();
        uint8_t d2 = msg.getData2();
        (void)type; (void)ch; (void)d1; (void)d2;
    }
} cb;

int main() {
    stdio_init_all();
    if (cyw43_arch_init()) return 1;
    midi.begin();
    midi.setCallbacks(cb);
    while (true) {
        midi.update();
        sleep_ms(1);
    }
}
```

`midi.update()` reads incoming data and dispatches to callbacks.

## With FineGrainedMIDI_Callbacks

For per-message-type handlers, use the CRTP pattern:

```cpp pico
struct Handlers : FineGrainedMIDI_Callbacks<Handlers> {
    void onNoteOn(Channel ch, uint8_t note, uint8_t velocity, Cable cable) {
        (void)ch; (void)note; (void)velocity; (void)cable;
    }
    void onControlChange(Channel ch, uint8_t cc, uint8_t value, Cable cable) {
        (void)ch; (void)cc; (void)value; (void)cable;
    }
};

Handlers handlers;
// midi.setCallbacks(handlers);
```

Available overrides: `onNoteOn`, `onNoteOff`, `onKeyPressure`, `onControlChange`, `onProgramChange`, `onChannelPressure`, `onPitchBend`, `onSystemExclusive`, `onTimeCodeQuarterFrame`, `onSongPosition`, `onSongSelect`, `onTuneRequest`, `onClock`, `onStart`, `onContinue`, `onStop`, `onActiveSensing`, `onSystemReset`.

## ChannelMessage accessors

| Method | Returns |
|--------|---------|
| `getMessageType()` | `MIDIMessageType` enum |
| `getChannel()` | `Channel` |
| `getData1()` | First data byte (note/CC number) |
| `getData2()` | Second data byte (velocity/value) |
| `getData14bit()` | 14-bit value (Pitch Bend) |
| `getCable()` | `Cable` |

## With the element system

MIDI input elements (`CCValue`, `NoteLED`, etc.) handle message matching and state management automatically — no callbacks needed. They update on each `Control_Surface.loop()` call.