vector for ATmega328 boards// 8 Apr 2009: Added support for ATmega1280 boards (Arduino Mega)#include <avr/io.h>#include <avr/interrupt.h>uint16_t syncPhaseAcc;uint16_t syncPhaseInc;uint16_t grainPhaseAcc;uint16_t grainPhaseInc;uint16_t grainAmp;uint8_t grainDecay;uint16_t grain2PhaseAcc;uint16_t grain2PhaseInc;uint16_t grain2Amp;uint8_t grain2Decay;// Map Analogue channels#define SYNC_CONTROL (4)#define GRAIN_FREQ_CONTROL (0)#define GRAIN_DECAY_CONTROL (2)#define GRAIN2_FREQ_CONTROL (3)#define GRAIN2_DECAY_CONTROL (1)// Changing these will also requires rewriting audioOn()#if defined(__AVR_ATmega8__)//// On old ATmega8 boards.// Output is on pin 11//#define LED_PIN 13#define LED_PORT PORTB#define LED_BIT 5#define PWM_PIN 11#define PWM_VALUE OCR2#define PWM_INTERRUPT TIMER2_OVF_vect#elif defined(__AVR_ATmega1280__)//// On the Arduino Mega// Output is on pin 3//#define LED_PIN 13#define LED_PORT PORTB#define LED_BIT 7#define PWM_PIN 3#define PWM_VALUE OCR3C#define PWM_INTERRUPT TIMER3_OVF_vect#else//// For modern ATmega168 and ATmega328 boards// Output is on pin 3//#define PWM_PIN 3#define PWM_VALUE OCR2B#define LED_PIN 13#define LED_PORT PORTB#define LED_BIT 5#define PWM_INTERRUPT TIMER2_OVF_vect#endif// Smooth logarithmic mapping//uint16_t antilogTable[] = { 64830,64132,63441,62757,62081,61413,60751,60097,59449,58809,58176,57549,56929,56316,55709,55109, 54515,53928,53347,52773,52204,51642,51085,50535,49991,49452,48920,48393,47871,47356,46846,46341, 45842,45348,44859,44376,43898,43425,42958,42495,42037,41584,41136,40693,40255,39821,39392,38968, 38548,38133,37722,37316,36914,36516,36123,35734,35349,34968,34591,34219,33850,33486,33125,32768};uint16_t mapPhaseInc(uint16_t input) { return (antilogTable[input & 0x3f]) >> (input >> 6);}// Stepped chromatic mapping//uint16_t midiTable[] = { 17,18,19,20,22,23,24,26,27,29,31,32,34,36,38,41,43,46,48,51,54,58,61,65,69,73, 77,82,86,92,97,103,109,115,122,129,137,145,154,163,173,183,194,206,218,231, 244,259,274,291,308,326,346,366,388,411,435,461,489,518,549,581,616,652,691, 732,776,822,871,923,978,1036,1097,1163,1232,1305,1383,1465,1552,1644,1742, 1845,1955,2071,2195,2325,2463,2610,2765,2930,3104,3288,3484,3691,3910,4143, 4389,4650,4927,5220,5530,5859,6207,6577,6968,7382,7821,8286,8779,9301,9854, 10440,11060,11718,12415,13153,13935,14764,15642,16572,17557,18601,19708,20879, 22121,23436,24830,26306};uint16_t mapMidi(uint16_t input) { return (midiTable[(1023-input) >> 3]);}// Stepped Pentatonic mapping//uint16_t pentatonicTable[54] = { 0,19,22,26,29,32,38,43,51,58,65,77,86,103,115,129,154,173,206,231,259,308,346, 411,461,518,616,691,822,923,1036,1232,1383,1644,1845,2071,2463,2765,3288, 3691,4143,4927,5530,6577,7382,8286,9854,11060,13153,14764,16572,19708,22121,26306};uint16_t mapPentatonic(uint16_t input) { uint8_t value = (1023-input) / (1024/53); return (pentatonicTable[value]);}void audioOn() {#if defined(__AVR_ATmega8__) // ATmega8 has different registers TCCR2 = _BV(WGM20) | _BV(COM21) | _BV(CS20); TIMSK = _BV(TOIE2);#elif defined(__AVR_ATmega1280__) TCCR3A = _BV(COM3C1) | _BV(WGM30); TCCR3B = _BV(CS30); TIMSK3 = _BV(TOIE3);#else // Set up PWM to 31.25kHz, phase accurate TCCR2A = _BV(COM2B1) | _BV(WGM20); TCCR2B = _BV(CS20); TIMSK2 = _BV(TOIE2);#endif}void setup() { pinMode(PWM_PIN,OUTPUT); audioOn(); pinMode(LED_PIN,OUTPUT);}void loop() { // The loop is pretty simple - it just updates the parameters for the oscillators. // // Avoid using any functions that make extensive use of interrupts, or turn interrupts off. // They will cause clicks and poops in the audio. // Smooth frequency mapping //syncPhaseInc = mapPhaseInc(analogRead(SYNC_CONTROL)) / 4; // Stepped mapping to MIDI notes: C, Db, D, Eb, E, F... //syncPhaseInc = mapMidi(analogRead(SYNC_CONTROL)); // Stepped pentatonic mapping: D, E, G, A, B syncPhaseInc = mapPentatonic(analogRead(SYNC_CONTROL)); grainPhaseInc = mapPhaseInc(analogRead(GRAIN_FREQ_CONTROL)) / 2; grainDecay = analogRead(GRAIN_DECAY_CONTROL) / 8; grain2PhaseInc = mapPhaseInc(analogRead(GRAIN2_FREQ_CONTROL)) / 2; grain2Decay = analogRead(GRAIN2_DECAY_CONTROL) / 4;}SIGNAL(PWM_INTERRUPT){ uint8_t value; uint16_t output; syncPhaseAcc += syncPhaseInc; if (syncPhaseAcc < syncPhaseInc) { // Time to start the next grain grainPhaseAcc = 0; grainAmp = 0x7fff; grain2PhaseAcc = 0; grain2Amp = 0x7fff; LED_PORT ^= 1 << LED_BIT; // Faster than using digitalWrite } // Increment the phase of the grain oscillators grainPhaseAcc += grainPhaseInc; grain2PhaseAcc += grain2PhaseInc; // Convert phase into a triangle wave value = (grainPhaseAcc >> 7) & 0xff; if (grainPhaseAcc & 0x8000) value = ~value; // Multiply by current grain amplitude to get sample output = value * (grainAmp >> 8); // Repeat for second grain value = (grain2PhaseAcc >> 7) & 0xff; if (grain2PhaseAcc & 0x8000) value = ~value; output += value * (grain2Amp >> 8); // Make the grain amplitudes decay by a factor every sample (exponential decay) grainAmp -= (grainAmp >> 8) * grainDecay; grain2Amp -= (grain2Amp >> 8) * grain2Decay; // Scale output to the available range, clipping if necessary output >>= 9; if (output > 255) output = 255; // Output to PWM (this is faster than using analogWrite) PWM_VALUE = output;}