Basic Arduino MIDI Drum Sequencer

Here's a simple-ish 808/606 style MIDI sequencer. I'd been looking for something like this for years. But most projects were either too complicated or used the arduino to also make the sounds. 

So yeah, the one I'm making for myself is more complicated, but here's something to hopefully get you started. 

 

I'm no programmer, but it seems to work.

 

//Simple MIDI Drum Sequencer 1.0 by Åke Strömer
//July 27 2021

#include <MIDI.h>
MIDI_CREATE_DEFAULT_INSTANCE();

//----------- IN & OUTPUTS ----------

//-------------MatrixMux-------------
#define clockPin 3 //Pin connected to RCLK/SH_CP/SHIFT REGISTER CLOCK     pin 11 of 74HC595
#define latchPin 4 //Pin connected to SRCLK/ST_CP/OUTPUT REGISTER CLOCK   pin 12 of 74HC595
#define dataPin 5 //Pin connected to SER/DS/INPUT                        pin 14 of 74HC595

//---------Knobs and Switches--------
#define clk 2

uint8_t SwRow[4] = {6, 7, 8, 9};

#define shiftSw 10
#define resetSw 11

uint8_t seqLength = 17;
uint8_t trackNr = 0;

//------------ MIDI -----------------
// 808              BD  SD  LT  MT  HT  MA  RS  CB  HH  OH
//                  0    1   2   3   4   5   6   7   8   9  10  11  12  13  14  15
uint8_t note[16] = {36, 38, 40, 41, 43, 39, 37, 56, 42, 46, 48, 50, 52, 54, 56, 58};
uint8_t midiCh = 1;

bool clkProgress = LOW;

uint8_t editMode = 0;
uint8_t stepNr = 0;
uint8_t seqNr;
uint8_t scanStep = 0;
bool dispStep[17] =  {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
//          [TRACK][STEP]
bool currentSeq[16][17] =
{
  // 0  1  2  3  4  5  6  7  8  9  10 11 12 13 14 15 16 SEQUENCE NR 0
  {0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0},
  {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
  {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
  {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
  {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
  {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
  {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
  {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
  {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
  {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
  {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
  {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
  {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
  {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
  {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
  {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
};

bool resetState = 0;
bool shiftState = 0;
bool lastShiftState = 0;


long time = 0;
long debounce = 300;

void setup()
{
  MIDI.begin(midiCh);
  for (uint8_t i = 0; i < 4; i++)
  {
    pinMode(SwRow[i], INPUT);
  }

  pinMode(latchPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
  pinMode(dataPin, OUTPUT);
  pinMode(shiftSw, INPUT_PULLUP);
  pinMode(resetSw, INPUT_PULLUP);

  seqNr = 0;
  attachInterrupt(digitalPinToInterrupt(clk), isr, RISING);
}

void loop()
{
  mux();
  readButtons();
  if (clkProgress == HIGH)
  {
    stepNr++;
    clkProgress = LOW;
    for (uint8_t i = 0; i < 10; i++)
    {
      if (currentSeq[i][stepNr] == 1)
      {
        MIDINoteOn(i);
      }
    }
  }

  if (stepNr >= 16)
  {
    stepNr = 0;
  }

  for (int i = 0; i < 17; i++)
  {
    dispStep[i] = 0;
  }
  if (editMode == 1)
  {
    dispStep[trackNr+1] = 1;
  }
  if (editMode == 2)
  {
    dispStep[midiCh] = 1;
  }
}

void readButtons()
{
  shiftState = digitalRead(shiftSw);
  resetState = digitalRead(resetSw);

  if (resetState  == LOW && shiftState == HIGH)
  {
    stepNr = 0;
  }
  else if (resetState  == HIGH && shiftState == LOW)
  {
    editMode = 1;
  }
  else if (resetState  == LOW && shiftState == LOW)
  {
    editMode = 2;
  }
  else
  {
    editMode = 0;
  }
}

void MIDINoteOn(uint8_t noteNr)
{
  switch (noteNr)
  {
    case 0:
      MIDI.sendNoteOn(note[0], 127, midiCh);
      MIDI.sendNoteOff(note[0], 127, midiCh);
      break;
    case 1:
      MIDI.sendNoteOn(note[1], 127, midiCh);
      MIDI.sendNoteOff(note[1], 127, midiCh);
      break;
    case 2:
      MIDI.sendNoteOn(note[2], 127, midiCh);
      MIDI.sendNoteOff(note[2], 127, midiCh);
      break;
    case 3:
      MIDI.sendNoteOn(note[3], 127, midiCh);
      MIDI.sendNoteOff(note[3], 127, midiCh);
      break;
    case 4:
      MIDI.sendNoteOn(note[4], 127, midiCh);
      MIDI.sendNoteOff(note[4], 127, midiCh);
      break;
    case 5:
      MIDI.sendNoteOn(note[5], 127, midiCh);
      MIDI.sendNoteOff(note[5], 127, midiCh);
      break;
    case 6:
      MIDI.sendNoteOn(note[6], 127, midiCh);
      MIDI.sendNoteOff(note[6], 127, midiCh);
      break;
    case 7:
      MIDI.sendNoteOn(note[7], 127, midiCh);
      MIDI.sendNoteOff(note[7], 127, midiCh);
      break;
    case 8:
      MIDI.sendNoteOn(note[8], 127, midiCh);
      MIDI.sendNoteOff(note[8], 127, midiCh);
      break;
    case 9:
      MIDI.sendNoteOn(note[9], 127, midiCh);
      MIDI.sendNoteOff(note[9], 127, midiCh);
      break;
    case 10:
      MIDI.sendNoteOn(note[10], 127, midiCh);
      MIDI.sendNoteOff(note[10], 127, midiCh);
      break;
    case 11:
      MIDI.sendNoteOn(note[11], 127, midiCh);
      MIDI.sendNoteOff(note[11], 127, midiCh);
      break;
    case 12:
      MIDI.sendNoteOn(note[12], 127, midiCh);
      MIDI.sendNoteOff(note[12], 127, midiCh);
      break;
    case 13:
      MIDI.sendNoteOn(note[13], 127, midiCh);
      MIDI.sendNoteOff(note[13], 127, midiCh);
      break;
    case 14:
      MIDI.sendNoteOn(note[14], 127, midiCh);
      MIDI.sendNoteOff(note[14], 127, midiCh);
      break;
    case 15:
      MIDI.sendNoteOn(note[15], 127, midiCh);
      MIDI.sendNoteOff(note[15], 127, midiCh);
      break;
    default:
      break;
  }
}

void mux()
{
  uint8_t dataToSend;
  bool swRead[4] = {0, 0, 0, 0};

  for (uint8_t x = 0; x < 4; x++) //Column Scanning
  {
    dataToSend = (16 << x);
    digitalWrite(latchPin, LOW);
    shiftOut(dataPin, clockPin, LSBFIRST, dataToSend);
    digitalWrite(latchPin, HIGH);

    //------------ READ SWITCHES -----------------

    for (uint8_t ySw = 0; ySw < 4; ySw++)
    {
      swRead[ySw] = digitalRead(SwRow[ySw]);
      if (swRead[ySw] == HIGH && millis() - time > debounce)
      {
        uint8_t swStep = 1 + x + 4 * ySw;
        if (editMode == 0) //WRITE MODE
        {
          if (currentSeq[trackNr][swStep] == 0)
          {
            currentSeq[trackNr][swStep] = 1;
          }
          else
          {
            currentSeq[trackNr][swStep] = 0;
          }
        }
        if (editMode == 1) //TRACK NR MODE
        {
          trackNr = swStep - 1;
        }
        if (editMode == 2) //MIDI Ch Mode
        {
          midiCh = swStep;
        }
        time = millis();
      }
    }

    //------------ LED'S -----------------

    for (uint8_t y = 0; y < 4; y++) //Row Scanning
    {
      bool thisLED;
      int scanStep = y + 1 + x * 4; //Fast matrix scan

      if (editMode == 1) //TRACK NR MODE
      {
        thisLED = dispStep[scanStep];
      }
      else if (editMode == 2) //MIDI Ch Mode
      {
        thisLED = dispStep[scanStep];
      }
      else
      {
        thisLED = currentSeq[trackNr][scanStep];
      }
      if (stepNr + 1 == scanStep)
      {
        (thisLED) ?  thisLED = 0 :  thisLED = 1;
      }
      (thisLED == 0) ? dataToSend = B00000000 : dataToSend = (16 << y) | (1 << x);

      digitalWrite(latchPin, LOW);
      shiftOut(dataPin, clockPin, LSBFIRST, dataToSend);
      digitalWrite(latchPin, HIGH);
    }
  }
}

void isr()
{
  clkProgress = HIGH;
}