4) Implementation of a shuffle rhythm function

Now we will implement a shuffle function to our Arduino Mega based step sequencer. A hardware switch will apply a HIGH signal to a digital input (ShufflePin is Pin 2) and to turn the shuffle on, where against a LOW signal at this pin means shuffle off. The rest is done by the software.

Parts list
-2 x Resistor 220 Ohm
-1 x Resistor 100 kOhm
-1 x Diode
-1 x opto coupler IC GNY17-2
-2 x 5-pole DIN female connector (180°)
-1 x MIDI cable
-1 x MIDI sync master (here: Roland TR-505)
-1 x MIDI sync slave (here: DIY synthesizer with MIDI-input)
-1 x Arduino (here: Arduino Mega. For this demo also Arduinos with less input and output channels will work)
-N x Potentiometer 10 kOhm
-Switch for turning shuffle on and off
-10 kOhm pull-down Resistor for the switch


Schematics



















Software

If the readout at the ShufflePin (pin 2) is LOW then the Shuffle_Flag=0 causing the ShuffleDelay to be 0. Then the sequencer runs as in the chapters before this one. However if the ShufflePin is set to HIGH by closing the respective switch, Shuffle_Flag will be 1. This means that every second 16th note will be delayed by 1 MIDI clock signals. The result is a shuffle rhythm. The effect can be increased, e.g. by setting ShuffleDelay = 2...4.

// Declaration of Varialbes
byte midi_start = 0xfa;
byte midi_stop = 0xfc;
byte midi_clock = 0xf8;
byte midi_continue = 0xfb;
int play_flag = 0;
byte data;
int clock_step;
int note;
int noteval;
int LowestNote;
int HighestNote;

int Note1;
int Note2;
int Note3;
int Note4;
int Note5;
int Note6;
int Note7;
int Note8;
int Note9;
int Note10;
int Note11;
int Note12;
int Note13;
int Note14;
int Note15;
int Note16;

int SeqLength;

int ShufflePin;
int Shuffle_Flag;
int ShuffleDelay;

// Initialization
void setup() {
Serial.begin(31250);
clock_step=0;
note = 0x3F;
noteval = 0;
LowestNote=36;
HighestNote=36+3*12; //3 Octaves over LowestNote

ShufflePin = 2;
pinMode(ShufflePin, INPUT); //Pin 0 for shuffle on/off as input
Shuffle_Flag = 0;
ShuffleDelay = 0;

Note1 = (96*1)/16-5;
Note2 = (96*2)/16-5;
Note3 = (96*3)/16-5;
Note4 = (96*4)/16-5;
Note5 = (96*5)/16-5;
Note6 = (96*6)/16-5;
Note7 = (96*7)/16-5;
Note8 = (96*8)/16-5;
Note9 = (96*9)/16-5;
Note10 = (96*10)/16-5;
Note11 = (96*11)/16-5;
Note12 = (96*12)/16-5;
Note13 = (96*13)/16-5;
Note14 = (96*14)/16-5;
Note15 = (96*15)/16-5;
Note16 = (96*16)/16-5;

SeqLength = 6*16; //Sequence length is 16*16th notes
}

// Main Programm
void loop() {

Shuffle_Flag = digitalRead(ShufflePin);

if(Shuffle_Flag == LOW) {
ShuffleDelay = 0;
}
if (Shuffle_Flag == HIGH){
ShuffleDelay = 2; // start every 2nd note two MIDI clock signals later
}

if(Serial.available() > 0) {
data = Serial.read();
if(data == midi_start) {
play_flag = 1;
clock_step=0;
}
else if(data == midi_continue) {
play_flag = 1;
}
else if(data == midi_stop) {
play_flag = 0;
clock_step=0;
sendMidiNote (0x80, note, 0x7F); //last note off
}
else if((data == midi_clock) && (play_flag == 1)) {
Sync();
}
}
}


// Functions

void Sync() { // play 8 fixed 16th notes, repeat after the cycle is finshed
clock_step = clock_step+1;

Note1 = (96*1)/16-5;
Note2 = (96*2)/16-5+ShuffleDelay;
Note3 = (96*3)/16-5;
Note4 = (96*4)/16-5+ShuffleDelay;
Note5 = (96*5)/16-5;
Note6 = (96*6)/16-5+ShuffleDelay;
Note7 = (96*7)/16-5;
Note8 = (96*8)/16-5+ShuffleDelay;
Note9 = (96*9)/16-5;
Note10 = (96*10)/16-5+ShuffleDelay;
Note11 = (96*11)/16-5;
Note12 = (96*12)/16-5+ShuffleDelay;
Note13 = (96*13)/16-5;
Note14 = (96*14)/16-5+ShuffleDelay;
Note15 = (96*15)/16-5;
Note16 = (96*16)/16-5+ShuffleDelay;

if (clock_step==Note1){ //1st step
sendMidiNote (0x80, note, 0x7F); //last note off
noteval = analogRead(0);
note = map(noteval, 0, 1023, LowestNote, HighestNote);
sendMidiNote (0x90, note, 0x7F); //note of this step on
}

if (clock_step==Note2){ //2nd step
sendMidiNote (0x80, note, 0x7F); //last note off
noteval = analogRead(1);
note = map(noteval, 0, 1023, LowestNote, HighestNote);
sendMidiNote (0x90, note, 0x7F); //note of this step on
}

if (clock_step==Note3){ //3nd step
sendMidiNote (0x80, note, 0x7F); //last note off
noteval = analogRead(2);
note = map(noteval, 0, 1023, LowestNote, HighestNote);
sendMidiNote (0x90, note, 0x7F); //note of this step on
}

if (clock_step==Note4){ //4nd step
sendMidiNote (0x80, note, 0x7F); //last note off
noteval = analogRead(3);
note = map(noteval, 0, 1023, LowestNote, HighestNote);
sendMidiNote (0x90, note, 0x7F); //note of this step on
}

if (clock_step==Note5){ //4nd step
sendMidiNote (0x80, note, 0x7F); //last note off
noteval = analogRead(4);
note = map(noteval, 0, 1023, LowestNote, HighestNote);
sendMidiNote (0x90, note, 0x7F); //note of this step on
}

if (clock_step==Note6){ //4nd step
sendMidiNote (0x80, note, 0x7F); //last note off
noteval = analogRead(5);
note = map(noteval, 0, 1023, LowestNote, HighestNote);
sendMidiNote (0x90, note, 0x7F); //note of this step on
}

if (clock_step==Note7){ //4nd step
sendMidiNote (0x80, note, 0x7F); //last note off
noteval = analogRead(6);
note = map(noteval, 0, 1023, LowestNote, HighestNote);
sendMidiNote (0x90, note, 0x7F); //note of this step on
}

if (clock_step==Note8){ //4nd step
sendMidiNote (0x80, note, 0x7F); //last note off
noteval = analogRead(7);
note = map(noteval, 0, 1023, LowestNote, HighestNote);
sendMidiNote (0x90, note, 0x7F); //note of this step on
}

if (clock_step==Note9){ //4nd step
sendMidiNote (0x80, note, 0x7F); //last note off
noteval = analogRead(8);
note = map(noteval, 0, 1023, LowestNote, HighestNote);
sendMidiNote (0x90, note, 0x7F); //note of this step on
}

if (clock_step==Note10){ //4nd step
sendMidiNote (0x80, note, 0x7F); //last note off
noteval = analogRead(9);
note = map(noteval, 0, 1023, LowestNote, HighestNote);
sendMidiNote (0x90, note, 0x7F); //note of this step on
}

if (clock_step==Note11){ //4nd step
sendMidiNote (0x80, note, 0x7F); //last note off
noteval = analogRead(10);
note = map(noteval, 0, 1023, LowestNote, HighestNote);
sendMidiNote (0x90, note, 0x7F); //note of this step on
}

if (clock_step==Note12){ //4nd step
sendMidiNote (0x80, note, 0x7F); //last note off
noteval = analogRead(11);
note = map(noteval, 0, 1023, LowestNote, HighestNote);
sendMidiNote (0x90, note, 0x7F); //note of this step on
}

if (clock_step==Note13){ //4nd step
sendMidiNote (0x80, note, 0x7F); //last note off
noteval = analogRead(12);
note = map(noteval, 0, 1023, LowestNote, HighestNote);
sendMidiNote (0x90, note, 0x7F); //note of this step on
}

if (clock_step==Note14){ //4nd step
sendMidiNote (0x80, note, 0x7F); //last note off
noteval = analogRead(13);
note = map(noteval, 0, 1023, LowestNote, HighestNote);
sendMidiNote (0x90, note, 0x7F); //note of this step on
}

if (clock_step==Note15){ //4nd step
sendMidiNote (0x80, note, 0x7F); //last note off
noteval = analogRead(14);
note = map(noteval, 0, 1023, LowestNote, HighestNote);
sendMidiNote (0x90, note, 0x7F); //note of this step on
}

if (clock_step==Note16){ //4nd step
sendMidiNote (0x80, note, 0x7F); //last note off
noteval = analogRead(15);
note = map(noteval, 0, 1023, LowestNote, HighestNote);
sendMidiNote (0x90, note, 0x7F); //note of this step on
}

else if (clock_step==SeqLength){
clock_step=0;
}
}

void sendMidiNote (byte midiCommand, byte noteValue, byte velocityValue){
Serial.print(midiCommand, BYTE);
Serial.print(noteValue, BYTE);
Serial.print(velocityValue, BYTE);
}