107 lines
3.1 KiB
C++
107 lines
3.1 KiB
C++
// Arduino Beat Detector By Damian Peckett 2015
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// License: Public Domain.
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// Our Global Sample Rate, 5000hz
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#define SAMPLEPERIODUS 200
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// defines for setting and clearing register bits
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#ifndef cbi
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#define cbi(sfr, bit) (_SFR_BYTE(sfr) &= ~_BV(bit))
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#endif
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#ifndef sbi
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#define sbi(sfr, bit) (_SFR_BYTE(sfr) |= _BV(bit))
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#endif
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bool beat_bool=true;
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void setup() {
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Serial.begin(9600);
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// Set ADC to 77khz, max for 10bit
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sbi(ADCSRA,ADPS2);
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cbi(ADCSRA,ADPS1);
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cbi(ADCSRA,ADPS0);
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//The pin with the LED
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// pinMode(2, OUTPUT);
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}
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// 20 - 200hz Single Pole Bandpass IIR Filter
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float bassFilter(float sample) {
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static float xv[3] = {0,0,0}, yv[3] = {0,0,0};
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xv[0] = xv[1]; xv[1] = xv[2];
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xv[2] = (sample) / 3.f; // change here to values close to 2, to adapt for stronger or weeker sources of line level audio
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yv[0] = yv[1]; yv[1] = yv[2];
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yv[2] = (xv[2] - xv[0])
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+ (-0.7960060012f * yv[0]) + (1.7903124146f * yv[1]);
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return yv[2];
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}
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// 10hz Single Pole Lowpass IIR Filter
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float envelopeFilter(float sample) { //10hz low pass
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static float xv[2] = {0,0}, yv[2] = {0,0};
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xv[0] = xv[1];
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xv[1] = sample / 50.f;
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yv[0] = yv[1];
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yv[1] = (xv[0] + xv[1]) + (0.9875119299f * yv[0]);
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return yv[1];
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}
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// 1.7 - 3.0hz Single Pole Bandpass IIR Filter
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float beatFilter(float sample) {
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static float xv[3] = {0,0,0}, yv[3] = {0,0,0};
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xv[0] = xv[1]; xv[1] = xv[2];
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xv[2] = sample / 2.7f;
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yv[0] = yv[1]; yv[1] = yv[2];
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yv[2] = (xv[2] - xv[0])
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+ (-0.7169861741f * yv[0]) + (1.4453653501f * yv[1]);
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return yv[2];
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}
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void loop() {
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unsigned long time = micros(); // Used to track rate
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float sample, value, envelope, beat, thresh;
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unsigned char i;
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for(i = 0;;++i){
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// Read ADC and center so +-512
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sample = (float)analogRead(1)-503.f;
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// Filter only bass component
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value = bassFilter(sample);
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// Take signal amplitude and filter
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if(value < 0)value=-value;
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envelope = envelopeFilter(value);
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// Every 200 samples (25hz) filter the envelope
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if(i == 200) {
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// Filter out repeating bass sounds 100 - 180bpm
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beat = beatFilter(envelope);
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// Threshold it based on potentiometer on AN1
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thresh = 0.02f * (float)analogRead(1);
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// If we are above threshold, light up LED
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if(beat > thresh) {
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if(beat_bool==true){
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//digitalWrite(2, HIGH);
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Serial.println("beat");
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beat_bool=false;
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}
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}
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else {
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beat_bool=true;
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Serial.println("-");// digitalWrite(2, LOW);
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}
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//Reset sample counter
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i = 0;
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}
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// Consume excess clock cycles, to keep at 5000 hz
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for(unsigned long up = time+SAMPLEPERIODUS; time > 20 && time < up; time = micros());
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}
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}
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