95 lines
1.8 KiB
C++
95 lines
1.8 KiB
C++
// Very basic Karplus-Strong
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// based on this explanation http://sites.music.columbia.edu/cmc/MusicAndComputers/chapter4/04_09.php
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#include <Adafruit_MCP4728.h>
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#include <Wire.h>
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Adafruit_MCP4728 mcp;
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#define nsamp 256
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#define dacmax 256
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unsigned int phase;
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unsigned int length;
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unsigned int repeats;
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int note = 0;
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int freqs[] = { 64, 56, 51, 48, 42, 38, 34, 32, 28, 25, 24, 21, 19, 17, 16 };
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int tune2[] = { 2, -1, -1, 2, -1, -1, 3, -1, 2, -1, -1, -1, 0, -1, -1, -1 };
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//int tune2[] = { 2, -1, -1, -1, -1, -1, -1, -1, 2, -1, -1, -1, 4, -1, -1, -1 };
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byte waveform[nsamp];
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int pd = 30;
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void setup() {
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cli();
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//set timer1 interrupt at 1Hz
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TCCR1A = 0;// set entire TCCR1A register to 0
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TCCR1B = 0;// same for TCCR1B
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TCNT1 = 0;//initialize counter value to 0
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// set compare match register for 1hz increments
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//OCR1A = 15624;// = (16*10^6) / (1*1024) - 1 (must be <65536)
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//OCR1A = 7812;// = (16*10^6) / (1*1024) - 1 (must be <65536)
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OCR1A = 2000;
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// turn on CTC mode
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TCCR1B |= (1 << WGM12);
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// Set CS10 and CS12 bits for 1024 escaler
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TCCR1B |= (1 << CS12) | (1 << CS10);
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// enable timer compare interrupt
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TIMSK1 |= (1 << OCIE1A);
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sei();
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if (!mcp.begin(0x64)) {
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while (1) {
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delay(100);
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}
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}
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randomSeed(analogRead(A0));
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mcp.setSpeed(800000L);
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phase=0;
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note=0;
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}
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ISR(TIMER1_COMPA_vect){//timer1
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if( tune2[note] > -1 ) {
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length=freqs[tune2[note]];
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for (int i=0; i<nsamp; ++i){
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waveform[i]=random(256);
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}
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}
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note++;
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if( note > 15 ) {
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note = 0;
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}
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pd = analogRead(A0) >> 4;
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}
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void loop() {
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byte s1, s2;
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int p0 = phase;
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int p1 = phase - pd;
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if( p1 < 0 ) {
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p1 += length;
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}
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phase += 1;
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if( phase >= length ) {
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phase = 0;
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}
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s1 = waveform[p1];
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s2 = waveform[p0];
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waveform[p0] = ( s1 & s2 ) + ((s1 ^ s2) >> 1);
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mcp.fastWrite(s1 << 4, 0, 0, 0);
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}
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