Add peak detection script

microcontroller/peak_detection.ino

@@ -0,0 +1,106 @@
+// Arduino Beat Detector By Damian Peckett 2015
+// License: Public Domain.
+
+// Our Global Sample Rate, 5000hz
+#define SAMPLEPERIODUS 200
+
+// defines for setting and clearing register bits
+#ifndef cbi
+#define cbi(sfr, bit) (_SFR_BYTE(sfr) &= ~_BV(bit))
+#endif
+#ifndef sbi
+#define sbi(sfr, bit) (_SFR_BYTE(sfr) |= _BV(bit))
+#endif
+
+bool beat_bool=true;
+
+void setup() {
+  Serial.begin(9600);
+    // Set ADC to 77khz, max for 10bit
+    sbi(ADCSRA,ADPS2);
+    cbi(ADCSRA,ADPS1);
+    cbi(ADCSRA,ADPS0);
+
+    //The pin with the LED
+  //  pinMode(2, OUTPUT);
+}
+
+// 20 - 200hz Single Pole Bandpass IIR Filter
+float bassFilter(float sample) {
+    static float xv[3] = {0,0,0}, yv[3] = {0,0,0};
+    xv[0] = xv[1]; xv[1] = xv[2]; 
+    xv[2] = (sample) / 3.f; // change here to values close to 2, to adapt for stronger or weeker sources of line level audio  
+    
+
+    yv[0] = yv[1]; yv[1] = yv[2]; 
+    yv[2] = (xv[2] - xv[0])
+        + (-0.7960060012f * yv[0]) + (1.7903124146f * yv[1]);
+    return yv[2];
+}
+
+// 10hz Single Pole Lowpass IIR Filter
+float envelopeFilter(float sample) { //10hz low pass
+    static float xv[2] = {0,0}, yv[2] = {0,0};
+    xv[0] = xv[1]; 
+    xv[1] = sample / 50.f;
+    yv[0] = yv[1]; 
+    yv[1] = (xv[0] + xv[1]) + (0.9875119299f * yv[0]);
+    return yv[1];
+}
+
+// 1.7 - 3.0hz Single Pole Bandpass IIR Filter
+float beatFilter(float sample) {
+    static float xv[3] = {0,0,0}, yv[3] = {0,0,0};
+    xv[0] = xv[1]; xv[1] = xv[2]; 
+    xv[2] = sample / 2.7f;
+    yv[0] = yv[1]; yv[1] = yv[2]; 
+    yv[2] = (xv[2] - xv[0])
+        + (-0.7169861741f * yv[0]) + (1.4453653501f * yv[1]);
+    return yv[2];
+}
+
+void loop() {
+    unsigned long time = micros(); // Used to track rate
+    float sample, value, envelope, beat, thresh;
+    unsigned char i;
+
+    for(i = 0;;++i){
+        // Read ADC and center so +-512
+        sample = (float)analogRead(1)-503.f;
+
+        // Filter only bass component
+        value = bassFilter(sample);
+
+        // Take signal amplitude and filter
+        if(value < 0)value=-value;
+        envelope = envelopeFilter(value);
+
+        // Every 200 samples (25hz) filter the envelope 
+        if(i == 200) {
+                // Filter out repeating bass sounds 100 - 180bpm
+                beat = beatFilter(envelope);
+
+                // Threshold it based on potentiometer on AN1
+                thresh = 0.02f * (float)analogRead(1);
+
+                // If we are above threshold, light up LED
+                if(beat > thresh) {
+                  if(beat_bool==true){
+                  //digitalWrite(2, HIGH);
+                  Serial.println("beat");
+                  beat_bool=false;
+                  }
+                }
+                else {
+                  beat_bool=true;
+                  Serial.println("-");// digitalWrite(2, LOW);
+                }
+
+                //Reset sample counter
+                i = 0;
+        }
+
+        // Consume excess clock cycles, to keep at 5000 hz
+        for(unsigned long up = time+SAMPLEPERIODUS; time > 20 && time < up; time = micros());
+    }  
+}