104 lines
2.1 KiB
C++
104 lines
2.1 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 256
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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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void setup() {
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// // Set a timer interrupt for the phase accumulation
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cli();//stop interrupts
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//set timer1 interrupt at 44Hz
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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 = 500; // = (16 * 10**6) / (44000) - 1
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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();//allow interrupts
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Serial.begin(115200);
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while (!Serial)
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delay(10); // will pause Zero, Leonardo, etc until serial console opens
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// Try to initialize!
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if (!mcp.begin(0x64)) {
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Serial.println("Failed to find MCP4728 chip");
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while (1) {
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delay(10);
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}
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} else {
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Serial.println("Adafruit MCP4728 initialised");
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}
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Wire.setClock(3400000L);
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freq=6600000;
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phase=0;
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calc_phase_inc();
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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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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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//calculate the phase increment.
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void calc_phase_inc(){
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phase_inc=0.268435456*nclk*freq;
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}
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ISR(TIMER1_COMPA_vect){// timer1 interrupt
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phase += phase_inc;
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}
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//regular running:
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void loop() {
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int redphase = phase >> 24;
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mcp.fastWrite(waveform[redphase] << 4, 0, 0, 0);
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//Serial.println(redphase);
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}
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