In this tutorial we show how to program an Arduino Uno board to realize a step sequencer.
The circuit used for this project is available on the web pageĀ of our Step Sequencer prototype.
/* ++ 6 STEP SEQUENCER ++ DESCRIPTION: Reads values from 6 potentiometers to change the pitch of any step of the sequencer tone generator. Change the pitch of each step with a potentiometer. CIRCUIT: Connect a speaker or piezo to pin number 13 and to ground; Connect the first lead of a potentiometer to 5v and the last to ground, the one in the middle to Analog Input pin 0; (Repeat for all the four potentiometers connecting the middle lead to Analog Input pins 0, 1, 2, 3, 4, 5); Connect a switch from digital port 3 and ground, put a 220 Ohm Resistor between the digital port 3 and 5V; For more information follow this link: https://www.artislab.it/it/step-sequencer/ This example code is for educational purpose and it is in the public domain. Author: Costantino Rizzuti 2016 Derived by a previous sketch made by Alessandro Contini & Paolo Cavagnolo */ // Tones table definition #define NOTE_B0 31 #define NOTE_C1 33 #define NOTE_CS1 35 #define NOTE_D1 37 #define NOTE_DS1 39 #define NOTE_E1 41 #define NOTE_F1 44 #define NOTE_FS1 46 #define NOTE_G1 49 #define NOTE_GS1 52 #define NOTE_A1 55 #define NOTE_AS1 58 #define NOTE_B1 62 #define NOTE_C2 65 #define NOTE_CS2 69 #define NOTE_D2 73 #define NOTE_DS2 78 #define NOTE_E2 82 #define NOTE_F2 87 #define NOTE_FS2 93 #define NOTE_G2 98 #define NOTE_GS2 104 #define NOTE_A2 110 #define NOTE_AS2 117 #define NOTE_B2 123 #define NOTE_C3 131 #define NOTE_CS3 139 #define NOTE_D3 147 #define NOTE_DS3 156 #define NOTE_E3 165 #define NOTE_F3 175 #define NOTE_FS3 185 #define NOTE_G3 196 #define NOTE_GS3 208 #define NOTE_A3 220 #define NOTE_AS3 233 #define NOTE_B3 247 #define NOTE_C4 262 #define NOTE_CS4 277 #define NOTE_D4 294 #define NOTE_DS4 311 #define NOTE_E4 330 #define NOTE_F4 349 #define NOTE_FS4 370 #define NOTE_G4 392 #define NOTE_GS4 415 #define NOTE_A4 440 #define NOTE_AS4 466 #define NOTE_B4 494 #define NOTE_C5 523 #define NOTE_CS5 554 #define NOTE_D5 587 #define NOTE_DS5 622 #define NOTE_E5 659 #define NOTE_F5 698 #define NOTE_FS5 740 #define NOTE_G5 784 #define NOTE_GS5 831 #define NOTE_A5 880 #define NOTE_AS5 932 #define NOTE_B5 988 #define NOTE_C6 1047 #define NOTE_CS6 1109 #define NOTE_D6 1175 #define NOTE_DS6 1245 #define NOTE_E6 1319 #define NOTE_F6 1397 #define NOTE_FS6 1480 #define NOTE_G6 1568 #define NOTE_GS6 1661 #define NOTE_A6 1760 #define NOTE_AS6 1865 #define NOTE_B6 1976 #define NOTE_C7 2093 #define NOTE_CS7 2217 #define NOTE_D7 2349 #define NOTE_DS7 2489 #define NOTE_E7 2637 #define NOTE_F7 2794 #define NOTE_FS7 2960 #define NOTE_G7 3136 #define NOTE_GS7 3322 #define NOTE_A7 3520 #define NOTE_AS7 3729 #define NOTE_B7 3951 #define NOTE_C8 4186 #define NOTE_CS8 4435 #define NOTE_D8 4699 #define NOTE_DS8 4978 </pre> // Declaration of tones used in the sequencer // Define here the note you want to play. // The first notes are mapped to the lowest position of the pots int pitch[] = { NOTE_C6, NOTE_E6, NOTE_G6, NOTE_C7, NOTE_E7, NOTE_G7, NOTE_C8}; // Declaration of variables int speaker = 9; // Speaker output pin // Variables used to calculate tempo int bpm=60; // set BPM // set Subdivision 1=quarter note; 0.5 ->eight note, .... float subdivision=1.5; int NumStep=4; // The Number of Steps (Max 6) int StepCounter=0; int potValue=0; // variable to store the value read from the pot unsigned int note=0; // variable to store the frequency of the note unsigned long IOI; // Inter-Onset Interval (time between two steps) unsigned long Duration; // notes duration void setup() { pinMode(4, INPUT); // Switch input pinMode(5, OUTPUT); // LED Output pinMode(speaker, OUTPUT); // Speaker Output //Inter-Onset Interval computed according bpm and subdivision IOI = subdivision*60000/(bpm); Duration=0.666*IOI; } void loop() { digitalWrite(5,HIGH); // Turn on the LED potValue = analogRead(StepCounter); // Read pot value // Discretization of the pot intervals - in order to assign the note if ((potValue>=0) && (potValue<128)) note = 0; // No Sound!!! if ((potValue>=128) && (potValue<256)) note = pitch[0]; if ((potValue>=256) && (potValue<384)) note = pitch[1]; if ((potValue>=384) && (potValue<512)) note = pitch[2]; if ((potValue>=512) && (potValue<640)) note = pitch[3]; if ((potValue>=640) && (potValue<768)) note = pitch[4]; if ((potValue>=768) && (potValue<896)) note = pitch[5]; if ((potValue>=896) && (potValue<1024)) note = pitch[6]; StepCounter++; // Increment the step if(StepCounter>=NumStep)StepCounter=0; // If StepCounter greater than NumStep back to 0 // If switch is on and pot in not full on the left if(note!=0&&digitalRead(4)==HIGH){ tone(speaker, note,Duration); // Play the note } delay(0.5*IOI); // Wait half period digitalWrite(5,LOW); // Turn off the LED delay(0.5*IOI); // Wait half period }
This code was used in the Oracolo sound object created by Costantino Rizzuti (2016). Watch some demonstration videos:
This simple code is very effective to start playing 8bit sounds, but it has a big problem about timing. In fact, the delay() function, used to control the temporal scanning of events, is rather imprecise (it has a resolution of a few thousandths of a second) and does not allow a regular succession of equidistant events over time. For this reason it is very difficult to use this code to create multiple sequences of notes that can be overlapped and mounted together to create tracks with more complex musical materials. To solve this problem, a new code has been created that uses a different timing system based on the use of the micros() function of Arduino which provides greater temporal accuracy of the order of microseconds.
Here some tracks created programming our PDSynth-00 prototype with this last step sequencer code.
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