Akai Force Rec Pedal w/ 8x8 Matrix Display (USB MIDI) - for Teensy LC

cowboy-akai-force-rec-pedal-matrix.ino

// ===============================================================
// Akai Force Rec Pedal w/ 8x8 Matrix Display (USB MIDI) - for Teensy LC
// "Cowboy" Ben Alman, 2021
// https://gist.github.com/cowboy/6c2230d54aea58577c5b7953ea86aebe
// ===============================================================

// Why does this exist?
//
// I designed this to circumvent an issue with the Akai Force where receiving
// an MMC Rec message signals that the loop should end at the end of the
// current measure BUT it also stops recording the current clip at the moment
// MMC Rec is received, NOT at the end of the measure, which makes it very hard
// to end loop recording via foot pedal in a musical way.
//
// Usage
//
// While recording:
// - Press the pedal to queue an MMC Rec message to be sent at the end of the
//   current measure. This will a) tell Force that it should set the loop length
//   to the end of the measure and b) turn recording mode off at the end of the
//   measure.
// - If you hold the pedal past the end of the measure, it will do "a" above
//   but keep recording mode on, instead of turing it off.
// - If you press the pedal again before the end of the current measure, it
//   will cancel the previous queued behavior.
//
// While not recording:
// - Press the pedal to queue an MMC Rec message to be sent at the end of
//   the current measure.
// - If you press the pedal again before the end of the current measure, it
//   will cancel the previous queued behavior.
//
// In order for this to work, you need to ensure the Force is set to send "MIDI
// Clock" and "Receive MMC" and be sure to enable "Sync" on the "Cowboy Akai
// Force Rec Pedal" Output Port. Also, note that because MIDI clock is dumb,
// this device can't know about any other time signature than what is hard-coded
// into it, which in this case is 4. I don't think Force supports anything other
// than 4/4 time, but if you want to change this, see BEATS_PER_MEASURE.
//
// How do I build this?
//
// This requires a momentary (normally open) foot pedal, like the Yamaha FC5, as
// well as an MAX7219-controlled 8x8 LED Matrix. See the photos in the comments
// to get an idea of how I built it. Here are the parts I used:
//
// * Teensy LC       https://www.pjrc.com/store/teensylc.html
// * 1/4" Mono Jack  https://www.switchcraft.com/Category_Multi.aspx?Parent=952
// * Yamaha FC5      https://smile.amazon.com/gp/product/B00005ML71
// * LED Matrix      https://smile.amazon.com/gp/product/B07VM6HXN5
// * Project Box     https://smile.amazon.com/gp/product/B0895HPW1T
// * USB adapter     https://www.amazon.com/gp/product/B07FL3MKLK
//
// How do I program this?
//
// Program with the Arduino IDE and Teensyduino. Their instructions are pretty
// comprehensive, but you may also want to read some guides or tutorials.
//
// * Arduino IDE     https://www.arduino.cc/en/software
// * Teensyduino     https://www.pjrc.com/teensy/teensyduino.html
// * MAX7219 Lib     https://github.com/GyverLibs/GyverMAX7219
// * (in English)    https://translate.google.com/translate?hl=en&sl=en&tl=en&u=https%3A%2F%2Fgithub.com%2FGyverLibs%2FGyverMAX7219
// * Bitmaps         https://bitmap-code-generator.benalman.com/
//
// Have fun!

#include <Bounce.h>
#include <GyverMAX7219.h>

// Uncomment the next line to simulate pressing play + running on boot
//#define RUN_TEST

// Change these pins if desired
const int SWITCH_PIN = 0;
const int LED_PIN = LED_BUILTIN;
const int MATRIX_DATA_PIN = 23;
const int MATRIX_CLK_PIN = 21;
const int MATRIX_CS_PIN = 22;

const int MATRIX_WIDTH = 8;
const int MATRIX_HEIGHT = 8;
const int MATRIX_BRIGHTNESS = 8;

MAX7219 < MATRIX_WIDTH, MATRIX_HEIGHT, MATRIX_CS_PIN, MATRIX_DATA_PIN, MATRIX_CLK_PIN > mtrx;

const uint8_t number_1_icon[] PROGMEM = {0x06, 0x0e, 0x16, 0x06, 0x06, 0x06, 0x06, 0x1f};
const uint8_t number_2_icon[] PROGMEM = {0x0e, 0x1b, 0x03, 0x03, 0x06, 0x0c, 0x18, 0x1f};
const uint8_t number_3_icon[] PROGMEM = {0x1e, 0x03, 0x03, 0x0e, 0x03, 0x03, 0x03, 0x1e};
const uint8_t number_4_icon[] PROGMEM = {0x03, 0x07, 0x0b, 0x1b, 0x1f, 0x03, 0x03, 0x03};

const uint8_t* const numbers[] PROGMEM = {number_1_icon, number_2_icon, number_3_icon, number_4_icon};

const uint8_t play_icon[] PROGMEM = {0xff, 0x81, 0xb1, 0xbd, 0xbd, 0xb1, 0x81, 0xff};
const uint8_t stop_icon[] PROGMEM = {0xff, 0x81, 0xbd, 0xbd, 0xbd, 0xbd, 0x81, 0xff};
const uint8_t ok_icon[] PROGMEM = {0x65, 0x95, 0x95, 0x96, 0x96, 0x95, 0x95, 0x65};
const uint8_t err_icon[] PROGMEM = {0x3d, 0x42, 0x85, 0x89, 0x91, 0xa1, 0x42, 0xbc};

const uint8_t robot_0_icon[] PROGMEM = {0x42, 0x7e, 0x81, 0xa5, 0x81, 0x7e, 0x3c, 0xff};
const uint8_t robot_1_icon[] PROGMEM = {0x42, 0x7e, 0x81, 0x81, 0x81, 0x7e, 0x3c, 0xff};

const uint8_t* const idle_screen_icons[] PROGMEM = {
  robot_0_icon, robot_0_icon, robot_0_icon, robot_0_icon, robot_0_icon, robot_0_icon, robot_0_icon, robot_0_icon,
  robot_0_icon, robot_0_icon, robot_0_icon, robot_0_icon, robot_0_icon, robot_0_icon, robot_0_icon, robot_0_icon,
  robot_0_icon, robot_0_icon, robot_0_icon, robot_0_icon, robot_0_icon, robot_0_icon, robot_0_icon, robot_0_icon,
  robot_1_icon, robot_0_icon, robot_1_icon, robot_0_icon,
};
const int idle_screen_icon_count = 28;

const int idle_screen_frame_delay = 20000;
const int stop_icon_frame_delay = 100000;

// Assume 4/4 time
int BEATS_PER_MEASURE = 4;
int PPQN = 24;
int PPSN = PPQN / 4;
int MAX_PULSES = PPQN * BEATS_PER_MEASURE;

Bounce button0 = Bounce(SWITCH_PIN, 5);

int counter = 0;
int error = 0;
int idle_screen_counter = 0;
int button_pressed = 0;
int rec_toggle_pending = 0;
int clock_running = 0;
int led_lit = 0;
int just_started = 0;
int just_stopped = 0;

void setup() {
  Serial.begin(115200);

  // Setup pins
  pinMode(SWITCH_PIN, INPUT_PULLUP);
  pinMode(LED_PIN, OUTPUT);

  // MIDI message handlers
  usbMIDI.setHandleClock(onClock);
  usbMIDI.setHandleStart(onStart);
  usbMIDI.setHandleContinue(onContinue);
  usbMIDI.setHandleStop(onStop);

  mtrx.begin();
  mtrx.setBright(MATRIX_BRIGHTNESS);
  mtrx.setRotation(3);

  draw_icon(ok_icon);
  blink(5);
  init_idle_screen();

  #ifdef RUN_TEST
    onStart();
  #endif
}

void led_on() {
  led_lit = 1;
  digitalWrite(LED_PIN, HIGH);
}

void led_off() {
  led_lit = 0;
  digitalWrite(LED_PIN, LOW);
}

void led_toggle() {
  if (led_lit) {
    led_off();
  } else {
    led_on();
  }
}

void blink(int count) {
  for (int i = 0; i < count; i++) {
    led_on();
    delay(50);
    led_off();
    delay(50);
  }
}

void test_matrix() {
  mtrx.clear();
  byte x, y;

  // light one LED at a time, scanning left to right
  // and top to bottom... useful for testing the matrix
  for (y = 0; y < MATRIX_HEIGHT; y++) {
    for (x = 0; x < MATRIX_WIDTH; x++) {
      mtrx.dot(x, y);
      mtrx.update();
      delay(100);
    }
  }
}

void loop() {
  if (just_stopped) {
    just_stopped++;
    if (just_stopped == stop_icon_frame_delay) {
      just_stopped = 0;
      init_idle_screen();
    }
  } else if (!clock_running && !error) {
    idle_screen();
  }

  button0.update();
  
  // Pedal pressed
  if (button0.risingEdge()) {
    button_pressed = 1;
    if (clock_running) {
      // Toggle pending state
      rec_toggle_pending = 1 - rec_toggle_pending;
      // Turn the LED on or off accordingly
      if (rec_toggle_pending) {
        led_on();
      } else {
        led_off();
      }
    } else {
      // Complain if pressed when the clock is not running
      blink(2);
    }
  }
  // Pedal released
  else if (button0.fallingEdge()) {
    button_pressed = 0;
  }
  
  usbMIDI.read();

  #ifdef RUN_TEST
    onClock();
    delay(50);
  #endif
}

void send_rec() {
  static uint8_t mmc_rec[6] = {0xF0, 0x7F, 0x7F, 0x06, 0x06, 0xF7};
  usbMIDI.sendSysEx(6, mmc_rec);
}

void clear_matrix() {
  mtrx.clear();
  mtrx.update();
}

void draw_icon(uint8_t *icon) {
  mtrx.clear();
  mtrx.drawBitmap(0, 0, icon, 8, 8);
  mtrx.update();
}

void draw_number(int i) {
  mtrx.clear();
  uint16_t ptr = pgm_read_word(&(numbers[i]));
  mtrx.drawBitmap(-3, 0, ptr, 8, 8);
}

void update_matrix() {
  int beat = counter / PPQN;
  int sixteenth = counter / PPSN;
  
  if (counter % PPQN == 0) {
    draw_number(beat);
  }
  
  for (int i = 0; i <= sixteenth % 4; i++) {
    int y1 = i * 2;
    int y2 = y1 + 1;
    if (rec_toggle_pending) {
      mtrx.fastLineH(y1, 6, 7);
      mtrx.fastLineH(y2, 6, 7);
    } else {
      int x1 = beat % 2 ? 6 : 7;
      int x2 = beat % 2 ? 7 : 6;
      mtrx.dot(x1, y1, 1);
      mtrx.dot(x2, y1, 0);
      mtrx.dot(x1, y2, 0);
      mtrx.dot(x2, y2, 1);
    }
  }
  mtrx.update();
}

void init_idle_screen() {
  idle_screen_counter = 0;
}

void idle_screen() {
  if (++idle_screen_counter % idle_screen_frame_delay == 0) {
    int i = idle_screen_counter / idle_screen_frame_delay;
    if (i == idle_screen_icon_count) {
      i = 0;
      idle_screen_counter = 0;
    }
    draw_icon(pgm_read_word(&(idle_screen_icons[i])));
  }
}

void onClock() {
  if (!clock_running) {
    if (!error) {
      error = 1;
      draw_icon(err_icon);
    }
    return;
  }

  if (++counter == MAX_PULSES) {
    counter = 0;
    // Send rec message if pending
    if (rec_toggle_pending) {
      rec_toggle_pending = 0;
      send_rec();
      // Since this is the beginning of the measure, send again
      // if the pedal is held down
      if (button_pressed) {
        send_rec();
      }
    }
  }

  if (counter % PPQN == 0 && just_started) {
    just_started = 0;
  }
  
  if (!just_started && counter % PPSN == 0) {
    update_matrix();
  }

  if (counter == 0) {
    led_on();
  } else if (counter % PPQN == 0 || counter == 2) {
    led_toggle();
  } else if (counter % PPQN == 1 || counter == 3) {
    led_toggle();
  } else if (counter == MAX_PULSES - 2) {
    led_off();
  }
}

void onStart() {
  Serial.println("Start");
  led_on();
  counter = 0;
  clock_running = 1;
  rec_toggle_pending = 0;
  just_started = 1;
  just_stopped = 0;
  draw_icon(play_icon);
  error = 0;
}

void onContinue() {
  Serial.println("Continue");
  clock_running = 1;
  error = 0;
}

void onStop() {
  Serial.println("Stop");
  led_off();
  clock_running = 0;
  rec_toggle_pending = 0;
  just_started = 0;
  just_stopped = 1;
  error = 0;
  draw_icon(stop_icon);
}

name.c

// To give your project a unique name, this code must be
// placed into a .c file (its own tab).  It can not be in
// a .cpp file or your main sketch (the .ino file).

#include "usb_names.h"

// Edit these lines to create your own name.  The length must
// match the number of characters in your custom name.

#define MIDI_NAME {'C', 'o', 'w', 'b', 'o', 'y', ' ', 'A', 'k', 'a', 'i', ' ', 'F', 'o', 'r', 'c', 'e', ' ', 'R', 'e', 'c', ' ', 'P', 'e', 'd', 'a', 'l'}
#define MIDI_NAME_LEN 27

// Do not change this part.  This exact format is required by USB.

struct usb_string_descriptor_struct usb_string_product_name = {
        2 + MIDI_NAME_LEN * 2,
        3,
        MIDI_NAME
};

The Force is almost perfect. Just a few tweaks. I watched a YouTuber named Youngr. He uses the Force to do some amazing loops and he seems to use foot pedals or something to stop a loop.