DIY drum machine sequencer with samples: Difference between revisions

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Revision as of 15:39, 7 July 2026

Introduction

Teensy based drum machine/ sequencer (groovebox?) with high quality samples

The knobs:

  • Bpm
  • Play/ record
  • Free rhythm / on beat
  • Track number selection
  • Length: 8 / 16 beats
  • number showing current step
  • Drums; shown below.
  • Display? showing the situation

Use potentiometer as Rotary selector switch.

The drums included (see https://en.wikipedia.org/wiki/List_of_percussion_instruments)

  1. Bass Drum https://samplefocus.com/samples/bass-drum-hit?search_id=199954966
  2. Bongo Drum
  3. Cajon Drum
  4. Castanets
  5. Conga Drums
  6. Cowbell https://samplefocus.com/samples/cowbell-f92f5f7b-5be6-44b7-bd5c-055dab612e55?search_id=199955024
  7. Cymbals https://samplefocus.com/samples/bright-soft-crash?search_id=199954863
  8. Djembe Drum
  9. Gongs
  10. Hi-hat
  11. Maracas
  12. Snare Drum https://samplefocus.com/samples/snare-drum-phonk-hit
  13. Steelpan https://samplefocus.com/samples/steel-pan-drum-15?search_id=199954909
  14. Tambourine
  15. Triangle
  16. Woodblock

Material

  • The plan. Note that also the svg version is available.

    The plan. Note that also the svg version is available.

  • 0.91" OLED Display module 128x32 px. I2C (SSD1306 driver). 36 x 12.5 (mm). Too small for my eyes.
  • Teensy 4.1 - No ethernet
    • 55 digital input/output pins, 35 PWM output pins
    • 18 analog input pins
    • 8 serial, 3 SPI, 3 I2C ports
    • 3 CAN Bus (1 with CAN FD)
    • Output 3.3V 250mA out
    • Vin 3.6 V to 5.5V
  • Audio Adapter board for Teensy 4.0 (Rev D) https://www.pjrc.com/store/teensy3_audio.html
  • 8 x Mini LED Arcade buttons 24 mm. (The parallel ~1K resistors are built in. Power the LED from a microcontroller pin or direct from 5V (eg a USB) with 10mA draw. With 3.3V power, 2mA per button.) See arcade button wiring guide https://himuragames.com/led-arcade-buttons-wiring-guide/ Thus 250mA/2mA gives many.
  • 3 x Illuminated Latching push button 16 mm

Wiring

Wiring the arcade buttons.

  • use the internal pullup resistor, connect one side of the button to GND and the other side to a pin on the Teensy. Use pinMode(pin, INPUT_PULLUP); to enable the internal pullup resistor (an internal pull up resistor [~47kΩ] is enabled, to keep the signal HIGH by default.)
  • Use Debouncing library: The high speed of the Teensy 4.1 makes it very sensitive to mechanical switch bounce. Use a library like Bounce2 for reliable button input.

Simple test program. Should use Bounce(pin, time); function. 

const int buttonPin1 = 32;  // the number of the pushbutton pin
const int buttonPin2 = 31;  // the number of the pushbutton pin
const int buttonPin3 = 30;  // the number of the pushbutton pin
const int buttonPin4 = 29;  // the number of the pushbutton pin

void setup() {
  Serial.begin(9600);

  pinMode(buttonPin1, INPUT_PULLUP);
  pinMode(buttonPin2, INPUT_PULLUP);
  pinMode(buttonPin3, INPUT_PULLUP);
  pinMode(buttonPin4, INPUT_PULLUP);
}

void loop() {
  if ( digitalRead(buttonPin1) == LOW ){
    Serial.println("1");
  }
  if ( digitalRead(buttonPin2) == LOW ){
    Serial.println("2");
  }
  if ( digitalRead(buttonPin3) == LOW ){
    Serial.println("3");
  }
  if ( digitalRead(buttonPin4) == LOW ){
    Serial.println("4");
  }
}

Potentiometer

  • Potentiometer + Pin to 3.3V
  • Potentiometer - Pin to GND
  • Potentiometer Data Pin

OLED Display module

  • I2C (Normally a 4.7K pullup resistor is connected between each signal and power, but the weak internal pullup resistors may be sufficient for short wires to a single device.)
    • SDA (18, Wire1 17, or 25)
    • SCL (19, Wire1 16, or 24)

Audio Board, I2C

  • SDA 18
  • SCL 19

Teensy Pins

Teensy 4.1 has a total of 55 input/output signal pins, from which 42 are easily accessible when used with a solderless breadboard. In teensy 4.1, 35 PWM pin support and 18 analog pins are present.

The pins 23 - 32 and 33 - 42 are easily available.

Teensy 4 Audio Library and Audio Board

Audio Board

https://www.pjrc.com/store/teensy3_audio.html

Audio Board is based on the SGTL5000 chip which in addition to ADC/DAC and amplifiers also offers some basic DSP functionality. The Adapter board has line input and output, mic input, and headphone output. Connect to Teensy using very short wires because of high-frequency master clock input (MCLK).

Audio Board connects to Teensy using 7 signals. The I2C pins SDA and SCL are used to control the chip and adjust parameters. Audio data uses I2S signals. DIN and DOUT and 3 clocks (LRCLK 44.1 kHZ, BCLK 1.41 or 2.82 MHZ and MCLK 11.29 MHz.

Signal Rev D, D2 (Teensy 4.x) Required For Function
MCLK 23 (MCLK1) Audio Audio Master Clock, 11.29 MHz
BCLK 21 (BCLK1) Audio Audio Bit Clock, 1.41 or 2.82 MHz
LRCLK 20 (LRCLK1) Audio Audio Left/Right Clock, 44.1 kHz
DIN 7 (OUT1A) Audio Output Audio Data from Teensy to Audio Shield. Goes to both headphone jack and Line-Out pins.
DOUT 8 (IN1) Audio Input Audio Data from Audio Shield to Teensy. Comes from either Microphone or Line-In pins.
SCL 19 Audio Config Control Clock (I2C)
SDA 18 Audio Config Control Data (I2C)
SCK 13 Optional Data SD or MEM Data Storage (SPI) Clock
MISO 12 Optional Data SD or MEM Data Storage (SPI) from SD/MEM to Teensy
MOSI 11 Optional Data SD or MEM Data Storage (SPI) from Teensy to SD/MEM
SDCS 10 Optional Data SD Card Chip Select (SPI) for SD Card
MEMCS 6 Optional Data MEM Chip Chip Select (SPI) for Memory Chip
Vol 15 / A1 Optional Knob Volume Thumbwheel (analog signal)

Play a sine wave

Test 1, almost from https://gist.github.com/mwicat/4c129fe835d58258688974d5e02ffb75 

#include <Audio.h>

AudioSynthWaveformSine sineWave; // Create a sine wave object
AudioOutputAnalog output; // Create an analog output object
AudioConnection patchCord(sineWave, output);

void setup() {
  AudioMemory(8); // Allocate memory for audio processing
  sineWave.frequency(440); // Set frequency to 440 Hz (A4)
  sineWave.amplitude(0.5); // Set amplitude
}

void loop() {
  // The sine wave will continuously play
}

Test2 Sine/Square Wave Generator: https://github.com/jameskeaveney/Teensy-SineWaveGenerator/blob/master/SineGen.ino

Teensy 4 Signal Generator

DDS (Direct Digital Synthesis) For teensy 3.5 https://github.com/EmaMaker/SignalGenerator-Teensy/blob/master/README.md

Harmonic distortion https://kennypeng.com/2020/11/23/teensy_harmonic_distortion.html https://github.com/colonelwatch/teensy-harmonic-distortion

Teensy Dynamic Sound Effects Processor https://cdn.hackaday.io/files/1638357009516640/Final%20Project_Complete.pdf

Hackaday tutorial

The tutorial: https://hackaday.io/project/8292-microcontroller-audio-workshop-had-supercon-2015 and the pdf file from https://raw.githubusercontent.com/PaulStoffregen/AudioWorkshop2015/master/workshop.pdf

Playing a file from SD card. File → Examples → Audio → Tutorial → Part_1_03_Playing_Music. Also available below (slightly modified version) and at https://github.com/PaulStoffregen/Audio/blob/master/examples/WavFilePlayer/WavFilePlayer.ino

  • Insert the Micro SD card from the card reader and into the Teensy Audio Shield before you upload the program. The music files are stored on this MicroSD card.

Three different audio outputs

  • AudioOutputI2S audioOutput;
  • AudioOutputSPDIF audioOutput;
  • AudioOutputAnalog audioOutput;

See the memory function at MemoryAndCpuUsage example

The patchCord1(playWav1, 0, audioOutput, 0); connects the left output channel (channel 0) of the WAV file player (playWav1) to the left input channel (channel 0) of the audio output (audioOutput). 

#include <Audio.h>
#include <Wire.h>
#include <SPI.h>
#include <SD.h>
#include <SerialFlash.h>

AudioPlaySdWav           playWav1;
AudioOutputI2S           audioOutput;

AudioConnection          patchCord1(playWav1, 0, audioOutput, 0);
AudioConnection          patchCord2(playWav1, 1, audioOutput, 1);
AudioControlSGTL5000     sgtl5000_1;

// Use these with the Teensy Audio Shield
#define SDCARD_CS_PIN    10
#define SDCARD_MOSI_PIN  7   // Teensy 4 ignores this, uses pin 11
#define SDCARD_SCK_PIN   14  // Teensy 4 ignores this, uses pin 13

void setup() {
  Serial.begin(9600);
  AudioMemory(8);

  sgtl5000_1.enable();
  sgtl5000_1.volume(0.5);

  SPI.setMOSI(SDCARD_MOSI_PIN);
  SPI.setSCK(SDCARD_SCK_PIN);
  if (!(SD.begin(SDCARD_CS_PIN))) {
    // stop here, but print a message repetitively
    while (1) {
      Serial.println("Unable to access the SD card");
      delay(500);
    }
  }
}

void playFile(const char *filename){
  Serial.print("Playing file: ");
  Serial.println(filename);

  playWav1.play(filename);
 
  delay(25);  // A brief delay for the library read WAV info

  // Simply wait for the file to finish playing.
  while (playWav1.isPlaying()) {
  }
}


void loop() {
  playFile("SDTEST1.WAV");  // filenames are always uppercase 8.3 format
  delay(500);
  playFile("SDTEST2.WAV");
  delay(500);
  playFile("SDTEST3.WAV");
  delay(500);
  playFile("SDTEST4.WAV");
  delay(1500);
}


Blink LED while Playing Music. File → Examples → Audio → Tutorial → Part_1_04_Blink_While_Playing

Use eg 

elapsedMillis blinkTime;
. . .
 if (blinkTime < 250) {
    digitalWrite(LED_PIN, LOW);
  } else if (blinkTime < 500) {
    digitalWrite(LED_PIN, HIGH);
  } else {
    blinkTime = 0; // start blink cycle over again
  }


Do More While Playing Music. File → Examples → Audio → Tutorial → Part_1_05_Do_More_While_Playing

  • The potentiometer controls the volume immediately, regardless of status of the LED.
  • The pushbuttons are read using the Bounce library

The GUI

Audio system design GUI https://www.pjrc.com/teensy/gui/ (page 9) From the main Arduino folder, navigate to these folders hardware / teensy / avr / libraries / Audio / gui. Inside the gui folder, open index.html

References

Teensy / Arduino/ ESP32 based drum machine/ sequencer with high quality samples. Use MIDI to transfer data from sequencer to synth. / Groovebox. References:

DIY Arduino Drum Synth + FREE SAMPLES! https://www.youtube.com/watch?v=xo-iN3tfE6o

https://www.instructables.com/MIDI-Drum-Machine/

ARDUINO 8 STEP KEYBOARD SEQUENCER FOR SYNTHESIZERS https://www.youtube.com/watch?v=9oGlCfwCoCw

Drum trigger sequencer. How To Make Your Own Drum Sequencer DIY The BIG BUTTON https://www.youtube.com/watch?v=6ArDGcUqiWM


https://diyelectromusic.com/2021/06/23/arduino-mozzi-sample-drum-sequencer/

Doof machine

https://github.com/gavD/arduino-drum-machine


Mozzi https://sensorium.github.io/Mozzi/gallery/


The Bastl Microgranny https://www.instructables.com/Microgranny-Sampler-Completely-Home-built-not-a-Ki/

SnapBeat https://www.hackster.io/hiro-akihabara/snapbeat-the-simple-lo-fi-sampler-5a3222

https://www.youtube.com/watch?v=U5Q8chfMglE

https://www.youtube.com/watch?v=YeKsXck8LDY

NI404 https://www.synthtopia.com/content/2024/01/21/the-ni404-is-an-open-source-diy-hardware-sampler-sequencer/

MOTHSYNTH https://www.mothsynth.com/

Samplotron https://hackaday.io/project/205253/components

Pushpin https://pushpin.kinga.dev/

Cosmic Loop https://github.com/kreiff/Cosmic_Loop

OpnBeat https://hackaday.io/project/190273-opnbeat-diy-lo-fi-sampler-with-isd1700-series

Launchpad https://github.com/pabolojo/DIY-Launchpad

Yorick https://bristol-communal-modular.github.io/yorick/?utm_source=chatgpt.com

Button test

//LEFT SIDE
const int buttonPin1 = 41;  // the number of the pushbutton pin
const int buttonPin2 = 40;  // the number of the pushbutton pin
const int buttonPin3 = 39;  // the number of the pushbutton pin
const int buttonPin4 = 38;  // the number of the pushbutton pin
const int buttonPin5 = 37;  // the number of the pushbutton pin
const int buttonPin6 = 36;  // the number of the pushbutton pin
const int buttonPin7 = 35;  // the number of the pushbutton pin
const int buttonPin8 = 34;  // the number of the pushbutton pin
//last is empty

//RIGHT SIDE
const int potentiometer1 = 24;  // ANALOG INPUT

const int togglePin1 = 25;  // the number of the pushbutton pin
const int togglePin2 = 26;  // the number of the pushbutton pin

void setup() {
  Serial.begin(9600);

  pinMode(buttonPin1, INPUT_PULLUP);
  pinMode(buttonPin2, INPUT_PULLUP);
  pinMode(buttonPin3, INPUT_PULLUP);
  pinMode(buttonPin4, INPUT_PULLUP);
  pinMode(buttonPin5, INPUT_PULLUP);
  pinMode(buttonPin6, INPUT_PULLUP);
  pinMode(buttonPin7, INPUT_PULLUP);
  pinMode(buttonPin8, INPUT_PULLUP);

  pinMode(togglePin1, INPUT_PULLUP);
  pinMode(togglePin2, INPUT_PULLUP);


}

int val;

void loop() {
  if ( digitalRead(buttonPin1) == LOW ){
    Serial.print("1, ");
  }
  if ( digitalRead(buttonPin2) == LOW ){
    Serial.print("2, ");
  }
  if ( digitalRead(buttonPin3) == LOW ){
    Serial.print("3, " );
  }
  if ( digitalRead(buttonPin4) == LOW ){
    Serial.print("4, " );
  }
  if ( digitalRead(buttonPin5) == LOW ){
    Serial.print("5, ");
  }
  if ( digitalRead(buttonPin6) == LOW ){
    Serial.print("6, ");
  }
  if ( digitalRead(buttonPin7) == LOW ){
    Serial.print("7, ");
  }
  if ( digitalRead(buttonPin8) == LOW ){
    Serial.print("8, ");
  }

  if ( digitalRead(togglePin1) == LOW ){
    Serial.print("t1, ");
  }
  if ( digitalRead(togglePin2) == LOW ){
    Serial.print("t2, ");
  }

  val = analogRead( potentiometer1 );
  Serial.println(val);

}


2

References

Teensy Best Practices: https://gist.github.com/somebox/d969f8a97e5a4362af5049ed554a9e69

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