117 lines
2.2 KiB
C++
117 lines
2.2 KiB
C++
//waveform generator
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// hacked from https://www.instructables.com/Arduino-Waveform-Generator-1/
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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 32
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#define dacmax 256
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const byte nclk = 200; // a guess
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long int freq; //frequency in Hz
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long unsigned int phase;
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long unsigned int phase_inc;
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int note = 0;
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int gate;
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int decay = 2;
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float pattern[4];
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long unsigned int pattern_inc[4];
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void setup() {
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TIMSK0 &= ~_BV(TOIE0); // disable timer0 overflow interrupt
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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 = 3905;// = (16*10^6) / (1*1024) - 1 (must be <65536)
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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 prescaler
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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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Serial.begin(115200);
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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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// mcp.setSpeed(400000L);
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// mcp.setSpeed(800000L);
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mcp.setSpeed(800000L);
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freq=440;
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phase=0;
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pattern[0] = 110.0;
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pattern[1] = 82.40688922821751;
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pattern[2] = 97.99885899543737;
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pattern[3] = 82.40688922821751;
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for( int i = 0; i < 4; i++ ) {
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pattern_inc[i] = pattern[i] * 975592.231884058;
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}
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setwave();
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}
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const float pi=3.14159265;
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byte waveform[nsamp];
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byte phaseb = 0;
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void setwave(){
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for (int isamp=0; isamp<nsamp; ++isamp){
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float phip=(isamp+0.5)/nsamp;
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float phi=2*pi*phip;
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int val=0;
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//saw
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val = dacmax * isamp / nsamp;
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//val = ( isamp < nsamp / 2 ) ? 0 : dacmax - 1;
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//sine
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//val=(sin(phi)+1.0)*dacmax/2;
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//val=((sin(phi)+0.333*sin(3*phi))/0.943+1)*dacmax/2;
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val=max(val,0);
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val=min(val,dacmax-1);
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waveform[isamp]=val;
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}
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}
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ISR(TIMER1_COMPA_vect){//timer1 interrupt 1Hz
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note += 1;
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if( note > 3 ) {
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note = 0;
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}
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phase_inc = pattern_inc[note];
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gate = 4095;
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}
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void loop() {
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phase += phase_inc;
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int redphase = phase >> 27;
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mcp.fastWrite(waveform[redphase] << 4, gate, 0, 0);
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if( gate > 0 ) {
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gate -= decay;
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}
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}
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