pico-example-midi.c

#include <stdio.h>
#include "pico/stdlib.h"
#include "hardware/gpio.h"
#include "pico/binary_info.h"

#include "bsp/board.h"
#include "tusb.h"

enum  {
  BLINK_NOT_MOUNTED = 250,
  BLINK_MOUNTED = 1000,
  BLINK_SUSPENDED = 2500,
};

static uint32_t blink_interval_ms = BLINK_NOT_MOUNTED;
const uint LED_PIN = PICO_DEFAULT_LED_PIN;

void led_blinking_task(void);
void midi_task(void);

int main() {
  board_init();

  tusb_init();

  while (1)
  {
    tud_task(); // tinyusb device task
    led_blinking_task();
    midi_task();
  }
}

//--------------------------------------------------------------------+
// Device callbacks
//--------------------------------------------------------------------+

// Invoked when device is mounted
void tud_mount_cb(void)
{
  blink_interval_ms = BLINK_MOUNTED;
}

// Invoked when device is unmounted
void tud_umount_cb(void)
{
  blink_interval_ms = BLINK_NOT_MOUNTED;
}

// Invoked when usb bus is suspended
// remote_wakeup_en : if host allow us  to perform remote wakeup
// Within 7ms, device must draw an average of current less than 2.5 mA from bus
void tud_suspend_cb(bool remote_wakeup_en)
{
  (void) remote_wakeup_en;
  blink_interval_ms = BLINK_SUSPENDED;
}

// Invoked when usb bus is resumed
void tud_resume_cb(void)
{
  blink_interval_ms = BLINK_MOUNTED;
}

//--------------------------------------------------------------------+
// MIDI Task
//--------------------------------------------------------------------+

// Variable that holds the current position in the sequence.
uint32_t note_pos = 0;

// Store example melody as an array of note values
uint8_t note_sequence[] =
{
  74,78,81,86,90,93,98,102,57,61,66,69,73,78,81,85,88,92,97,100,97,92,88,85,81,78,
  74,69,66,62,57,62,66,69,74,78,81,86,90,93,97,102,97,93,90,85,81,78,73,68,64,61,
  56,61,64,68,74,78,81,86,90,93,98,102
};

void midi_task(void)
{
  static uint32_t start_ms = 0;
  uint8_t msg[3];

  // send note every 1000 ms
  if (board_millis() - start_ms < 286) return; // not enough time
  start_ms += 286;

  // Previous positions in the note sequence.
  int previous = note_pos - 1;

  // If we currently are at position 0, set the
  // previous position to the last note in the sequence.
  if (previous < 0) previous = sizeof(note_sequence) - 1;

  // Send Note On for current position at full velocity (127) on channel 1.
  msg[0] = 0x90;                    // Note On - Channel 1
  msg[1] = note_sequence[note_pos]; // Note Number
  msg[2] = 127;                     // Velocity
  tud_midi_n_stream_write(0, 0, msg, 3);

  // Send Note Off for previous note.
  msg[0] = 0x80;                    // Note Off - Channel 1
  msg[1] = note_sequence[previous]; // Note Number
  msg[2] = 0;                       // Velocity
  tud_midi_n_stream_write(0, 0, msg, 3);

  // Increment position
  note_pos++;

  // If we are at the end of the sequence, start over.
  if (note_pos >= sizeof(note_sequence)) note_pos = 0;
}

//--------------------------------------------------------------------+
// BLINKING TASK
//--------------------------------------------------------------------+
void led_blinking_task(void)
{
  static uint32_t start_ms = 0;
  static bool led_state = false;

  // Blink every interval ms
  if ( board_millis() - start_ms < blink_interval_ms) return; // not enough time
  start_ms += blink_interval_ms;

  board_led_write(led_state);
  led_state = 1 - led_state; // toggle
}