Arduino Beat Detector

1// Arduino Beat Detector By Damian Peckett 2015
2// License: Public  Domain.
3
4// Our Global Sample Rate, 5000hz
5#define SAMPLEPERIODUS 200
6
7//  defines for setting and clearing register bits
8#ifndef cbi
9#define cbi(sfr,  bit) (_SFR_BYTE(sfr) &= ~_BV(bit))
10#endif
11#ifndef sbi
12#define sbi(sfr,  bit) (_SFR_BYTE(sfr) |= _BV(bit))
13#endif
14
15void setup() {
16    // Set  ADC to 77khz, max for 10bit
17    sbi(ADCSRA,ADPS2);
18    cbi(ADCSRA,ADPS1);
19    cbi(ADCSRA,ADPS0);
20
21    //The pin with the LED
22    pinMode(2, OUTPUT);
23}
24
25//  20 - 200hz Single Pole Bandpass IIR Filter
26float bassFilter(float sample) {
27    static float xv[3] = {0,0,0}, yv[3] = {0,0,0};
28    xv[0] = xv[1]; xv[1] =  xv[2]; 
29    xv[2] = (sample) / 3.f; // change here to values close to 2, to adapt  for stronger or weeker sources of line level audio  
30    
31
32    yv[0] =  yv[1]; yv[1] = yv[2]; 
33    yv[2] = (xv[2] - xv[0])
34        + (-0.7960060012f  * yv[0]) + (1.7903124146f * yv[1]);
35    return yv[2];
36}
37
38// 10hz Single  Pole Lowpass IIR Filter
39float envelopeFilter(float sample) { //10hz low pass
40    static float xv[2] = {0,0}, yv[2] = {0,0};
41    xv[0] = xv[1]; 
42    xv[1]  = sample / 50.f;
43    yv[0] = yv[1]; 
44    yv[1] = (xv[0] + xv[1]) + (0.9875119299f  * yv[0]);
45    return yv[1];
46}
47
48// 1.7 - 3.0hz Single Pole Bandpass IIR  Filter
49float beatFilter(float sample) {
50    static float xv[3] = {0,0,0},  yv[3] = {0,0,0};
51    xv[0] = xv[1]; xv[1] = xv[2]; 
52    xv[2] = sample / 2.7f;
53    yv[0] = yv[1]; yv[1] = yv[2]; 
54    yv[2] = (xv[2] - xv[0])
55        + (-0.7169861741f  * yv[0]) + (1.4453653501f * yv[1]);
56    return yv[2];
57}
58
59void loop()  {
60    unsigned long time = micros(); // Used to track rate
61    float sample,  value, envelope, beat, thresh;
62    unsigned char i;
63
64    for(i = 0;;++i){
65        // Read ADC and center so +-512
66        sample = (float)analogRead(0)-503.f;
67
68        // Filter only bass component
69        value = bassFilter(sample);
70
71        // Take signal amplitude and filter
72        if(value < 0)value=-value;
73        envelope = envelopeFilter(value);
74
75        // Every 200 samples (25hz)  filter the envelope 
76        if(i == 200) {
77                // Filter out  repeating bass sounds 100 - 180bpm
78                beat = beatFilter(envelope);
79
80                // Threshold it based on potentiometer on AN1
81                thresh  = 0.02f * (float)analogRead(1);
82
83                // If we are above threshold,  light up LED
84                if(beat > thresh) digitalWrite(2, HIGH);
85                else  digitalWrite(2, LOW);
86
87                //Reset sample counter
88                i  = 0;
89        }
90
91        // Consume excess clock cycles, to keep at 5000  hz
92        for(unsigned long up = time+SAMPLEPERIODUS; time > 20 && time < up;  time = micros());
93    }  
94}
95

1// Arduino Beat Detector By Damian Peckett 2015
2// License: Public
3  Domain.
4
5// Our Global Sample Rate, 5000hz
6#define SAMPLEPERIODUS 200
7
8//
9  defines for setting and clearing register bits
10#ifndef cbi
11#define cbi(sfr,
12  bit) (_SFR_BYTE(sfr) &= ~_BV(bit))
13#endif
14#ifndef sbi
15#define sbi(sfr,
16  bit) (_SFR_BYTE(sfr) |= _BV(bit))
17#endif
18
19void setup() {
20    // Set
21  ADC to 77khz, max for 10bit
22    sbi(ADCSRA,ADPS2);
23    cbi(ADCSRA,ADPS1);
24
25    cbi(ADCSRA,ADPS0);
26
27    //The pin with the LED
28    pinMode(2, OUTPUT);
29}
30
31//
32  20 - 200hz Single Pole Bandpass IIR Filter
33float bassFilter(float sample) {
34
35    static float xv[3] = {0,0,0}, yv[3] = {0,0,0};
36    xv[0] = xv[1]; xv[1] =
37  xv[2]; 
38    xv[2] = (sample) / 3.f; // change here to values close to 2, to adapt
39  for stronger or weeker sources of line level audio  
40    
41
42    yv[0] =
43  yv[1]; yv[1] = yv[2]; 
44    yv[2] = (xv[2] - xv[0])
45        + (-0.7960060012f
46  * yv[0]) + (1.7903124146f * yv[1]);
47    return yv[2];
48}
49
50// 10hz Single
51  Pole Lowpass IIR Filter
52float envelopeFilter(float sample) { //10hz low pass
53
54    static float xv[2] = {0,0}, yv[2] = {0,0};
55    xv[0] = xv[1]; 
56    xv[1]
57  = sample / 50.f;
58    yv[0] = yv[1]; 
59    yv[1] = (xv[0] + xv[1]) + (0.9875119299f
60  * yv[0]);
61    return yv[1];
62}
63
64// 1.7 - 3.0hz Single Pole Bandpass IIR
65  Filter
66float beatFilter(float sample) {
67    static float xv[3] = {0,0,0},
68  yv[3] = {0,0,0};
69    xv[0] = xv[1]; xv[1] = xv[2]; 
70    xv[2] = sample / 2.7f;
71
72    yv[0] = yv[1]; yv[1] = yv[2]; 
73    yv[2] = (xv[2] - xv[0])
74        + (-0.7169861741f
75  * yv[0]) + (1.4453653501f * yv[1]);
76    return yv[2];
77}
78
79void loop()
80  {
81    unsigned long time = micros(); // Used to track rate
82    float sample,
83  value, envelope, beat, thresh;
84    unsigned char i;
85
86    for(i = 0;;++i){
87
88        // Read ADC and center so +-512
89        sample = (float)analogRead(0)-503.f;
90
91
92        // Filter only bass component
93        value = bassFilter(sample);
94
95
96        // Take signal amplitude and filter
97        if(value < 0)value=-value;
98
99        envelope = envelopeFilter(value);
100
101        // Every 200 samples (25hz)
102  filter the envelope 
103        if(i == 200) {
104                // Filter out
105  repeating bass sounds 100 - 180bpm
106                beat = beatFilter(envelope);
107
108
109                // Threshold it based on potentiometer on AN1
110                thresh
111  = 0.02f * (float)analogRead(1);
112
113                // If we are above threshold,
114  light up LED
115                if(beat > thresh) digitalWrite(2, HIGH);
116                else
117  digitalWrite(2, LOW);
118
119                //Reset sample counter
120                i
121  = 0;
122        }
123
124        // Consume excess clock cycles, to keep at 5000
125  hz
126        for(unsigned long up = time+SAMPLEPERIODUS; time > 20 && time < up;
127  time = micros());
128    }  
129}
130