text: #include <stdint.h>
  
  /* callback prototype */
  typedef void (midi_msg_handle_fn_t)(uint8_t status, const uint8_t data[], int len);
  
  // initialises the callback
  void midi_msg_init(midi_msg_handle_fn_t *fn);
  // processes one byte
  void midi_msg_proc(uint8_t b);
  
  
  