88 lines
2.7 KiB
C++
88 lines
2.7 KiB
C++
/*
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Based on the 'stomp_updown" from openmusiclabs.com
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this program plays through a sample buffer, first forward at
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double rate, and then backwards at single rate. it changes
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direction at the buffer boundary.
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*/
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//defining harware resources.
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#define LED 13
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#define FOOTSWITCH 12
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#define TOGGLE 2
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#define PUSHBUTTON_1 A5
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#define PUSHBUTTON_2 A4
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//defining the output PWM parameters
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#define PWM_FREQ 0x00FF // pwm frequency - 31.3KHz
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#define PWM_MODE 0 // Fast (1) or Phase Correct (0)
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#define PWM_QTY 2 // 2 PWMs in parallel
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#define SIZE 1000 // buffer size, make lower if it clicks
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int buffer[SIZE]; // data buffer
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unsigned int location = 0; // current buffer location
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unsigned int offset = 0; // distance to current location
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byte dir = 0; // direction of travel in buffer
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int data_buffer = 0x8000;
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void setup() {
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//setup IO
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pinMode(FOOTSWITCH, INPUT_PULLUP);
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pinMode(TOGGLE, INPUT_PULLUP);
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pinMode(PUSHBUTTON_1, INPUT_PULLUP);
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pinMode(PUSHBUTTON_2, INPUT_PULLUP);
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pinMode(LED, OUTPUT);
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// setup ADC
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ADMUX = 0x60; // left adjust, adc0, internal vcc
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ADCSRA = 0xe5; // turn on adc, ck/32, auto trigger
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ADCSRB = 0x07; // t1 capture for trigger
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DIDR0 = 0x01; // turn off digital inputs for adc0
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// setup PWM
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TCCR1A = (((PWM_QTY - 1) << 5) | 0x80 | (PWM_MODE << 1)); //
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TCCR1B = ((PWM_MODE << 3) | 0x11); // ck/1
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TIMSK1 = 0x20; // interrupt on capture interrupt
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ICR1H = (PWM_FREQ >> 8);
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ICR1L = (PWM_FREQ & 0xff);
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DDRB |= ((PWM_QTY << 1) | 0x02); // turn on outputs
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sei(); // turn on interrupts - not really necessary with arduino
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}
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void loop() {
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}
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ISR(TIMER1_CAPT_vect) { // all processing happens here
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// output the last value calculated
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OCR1AL = ((data_buffer + 0x8000) >> 8); // convert to unsigned, send out high byte
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OCR1BL = data_buffer; // send out low byte
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// get ADC data
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byte temp1 = ADCL; // you need to fetch the low byte first
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byte temp2 = ADCH; // yes it needs to be done this way
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int input = ((temp2 << 8) | temp1) + 0x8000; // make a signed 16b value
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buffer[location] = input; // store current sample
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location++; // go to next location
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if (location >= SIZE) location = 0; // deal with boundary
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unsigned int temp = location + offset; // find playback location
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if (temp >= SIZE) temp -= SIZE; // boundary wrap
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data_buffer = buffer[temp]; // fetch sample
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if (dir) { // increment until at buffer boundary
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if (offset >= (SIZE - 4)) {
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dir = 0;
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offset--;
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}
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else offset++;
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}
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else { // decrement till reaching boundary from other side
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if (offset <= 4) {
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dir = 1;
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offset--;
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}
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else offset -= 2;
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}
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}
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