127 lines
4 KiB
C++
127 lines
4 KiB
C++
/*
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Based on the "stomp_shifter" from openmusiclabs;
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this is a pitch shifter program. it indexes through a sample
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buffer at either a slower or faster rate than the incoming
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samples. the buffer boundaries are dealt with by having to samples
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being played back simultaneously, each from opposite sides of the
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buffer. the volume of each is set by the distance to the boundary.
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the rotary encoder sets the speed of playback.
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*/
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#include "mult16x16.h"
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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 // make this smaller if it clicks
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int buffer[SIZE]; // sample buffer
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unsigned int location = 0; // current sample input position
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unsigned int offset = 0; // playback sample offset from input
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byte shift = 0x80;
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unsigned int fractional = 0x80; // fractional sample rate
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int data_buffer = 0x80;
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int counter=0;
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int toggle_position=0;
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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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//Turn on the LED if the effect is ON.
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if (digitalRead(FOOTSWITCH)) digitalWrite(LED, HIGH);
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else digitalWrite(LED, LOW);
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//nothing else here, all happens in the Timer 1 interruption.
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}
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ISR(TIMER1_CAPT_vect) {
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// output data
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OCR1AL = ((data_buffer >> 8) + 0x80);
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OCR1BL = data_buffer; // output the bottom 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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//BUTTONS
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counter++; //the pushbuttons are checked every 2500 times.
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if(counter==2500)
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{
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counter=0;
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if (!digitalRead(PUSHBUTTON_2)) {
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shift++;
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if (shift >= 0xfe) shift = 0xfe;
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}
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if (!digitalRead(PUSHBUTTON_1)) {
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shift--;
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if (shift <= 1) shift = 1;
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}
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}
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//Depending on the Toggle switch position, the effect is reseted)
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if(digitalRead(TOGGLE)!=toggle_position)
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{
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toggle_position = digitalRead(TOGGLE); //update the new value
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shift=0x80;
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}
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buffer[location] = input; // store incoming data
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location++; // increment storage location
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if (location >= SIZE) location = 0; // boundary wrap
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unsigned int temp = location + offset; // find next sample
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if (temp >= SIZE) temp -= SIZE; // boundary wrap
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int output = buffer[temp]; // fetch sample
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temp += (SIZE >> 1); // find sample on opposite side of buffer
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if (temp >= SIZE) temp -= SIZE; // boundary wrap
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int output2 = buffer[temp]; // fetch sample
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unsigned int distance; // find distance to buffer boundary
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if (offset > (SIZE >> 1)) distance = SIZE - offset;
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else distance = offset;
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int result; // average the 2 samples based on distance to boundary
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MultiSU16X16toH16(result, output, (distance << 7));
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MultiSU16X16toH16(output, output2, (((SIZE >> 1) - distance) << 7));
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output += result;
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fractional += shift; // increment offset
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if (fractional >= 0x0080) {
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offset += (fractional >> 7);
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fractional &= 0x007f;
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}
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if (offset >= SIZE) offset -= SIZE; // boundary wrap
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// save data
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data_buffer = output;
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}
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