112 lines
3.5 KiB
C++
112 lines
3.5 KiB
C++
/*
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Based on the stomp_tremolo.pde from openmusiclabs.com
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this program does a tremolo effect. it uses a sinewave stored
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in program memory to modulate the signal. the rate at which
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it goes through the sinewave is set by the push buttons,
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which is min/maxed by the speed value.
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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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const char * const sinewave[] PROGMEM = {
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// this file is stored in StompShield and is a 1024 value
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// sinewave lookup table of signed 16bit integers
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// you can replace it with your own waveform if you like
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#include "mult16x16.h"
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#include "sinetable.inc"
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};
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unsigned int location = 0; // incoming data buffer pointer
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unsigned int fractional = 0x00; // fractional sample position
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int data_buffer; // temporary data storage to give a 1 sample buffer
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int input, speed=20;
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int counter=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) { // 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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//BUTTONS
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counter++; //to save resources, the pushbuttons are checked every 1000 times.
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if(counter==1000)
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{
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counter=0;
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if (!digitalRead(PUSHBUTTON_2)) {
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if (speed<1024)speed=speed+1; //increase speed
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digitalWrite(LED, LOW); //blinks the led
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}
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if (!digitalRead(PUSHBUTTON_1)) {
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if (speed>0)speed=speed-1; //decrease speed
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digitalWrite(LED, LOW); //blinks the led
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}
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}
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fractional += speed; // increment sinewave lookup counter
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if (fractional >= 0x0100) { // if its large enough to go to next sample
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fractional &= 0x00ff; // round off
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location += 1; // go to next location
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location &= 0x03ff; // fast boundary wrap for 2^n boundaries
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}
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// fetch current sinewave value
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int amplitude = pgm_read_word_near(sinewave + location);
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amplitude += 0x8000; // convert to unsigned
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int output;
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MultiSU16X16toH16(output, input, amplitude);
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// save value for playback next interrupt
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data_buffer = output;
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}
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