I am fairly new to programming, and as I have a fascination for music I thought to start with building a simple sequencer using codes from the web.
Now I found a perfect code but somehow it does not behave as it needs to and I hope to get some advice here in order to learn more and eventually build my own synthesizer!
/* analog inputs:
* A0 pitch step 1 (syncPhaseInc)
* A1 pitch step 2
* A2 pitch step 3
* A3 pitch step 4
* A4 tempo
* A5 effect (grainPhaseInc)
* plus volume potentiometer
*
* audio out via 220 ohm resistor to 3.5mm jack
* audio out via 10K/10K voltage divider and 10K volume pot and 10uF cap to internal mono amp with speaker
* power switch on amp
* built with Arduino Nano on perf board powered by USB cable
*/
#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;
// 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__) || defined(__AVR_ATmega2560__)
//
// 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
}
long counter = 0;
long tempo;
int pattern = 0;
const byte pat0 = 4;
const byte pat1 = 5;
const byte pat2 = 6;
const byte pat3 = 7;
void setup() {
pinMode(PWM_PIN, OUTPUT);
audioOn();
pinMode(LED_PIN, OUTPUT);
pinMode(pat0, OUTPUT);
pinMode(pat1, OUTPUT);
pinMode(pat2, OUTPUT);
pinMode(pat3, OUTPUT);
digitalWrite(pat0, LOW);
digitalWrite(pat1, LOW);
digitalWrite(pat2, LOW);
digitalWrite(pat3, LOW);
// presets for 3 less important pots
grainDecay = 200 / 8;
grain2PhaseInc = mapPhaseInc(200) / 2;
grain2Decay = 200 / 4;
}
void loop() {
tempo = map(analogRead(A4), 0, 1023, 100, 4000);
counter++;
if (counter > tempo) {
counter = 0;
if (pattern == 4) {
pattern = 0;
}
switch (pattern) {
case 0:
syncPhaseInc = mapPentatonic(analogRead(A0));
digitalWrite(pat3, LOW);
digitalWrite(pat0, HIGH);
break;
case 1:
syncPhaseInc = mapPentatonic(analogRead(A1));
digitalWrite(pat0, LOW);
digitalWrite(pat1, HIGH);
break;
case 2:
syncPhaseInc = mapPentatonic(analogRead(A2));
digitalWrite(pat1, LOW);
digitalWrite(pat2, HIGH);
break;
case 3:
syncPhaseInc = mapPentatonic(analogRead(A3));
digitalWrite(pat2, LOW);
digitalWrite(pat3, HIGH);
break;
}
grainPhaseInc = mapPhaseInc(analogRead(A5)) / 2;
pattern++;
}
}
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;
}
- one thing I cannot explain is that the sound output pin is different from the one in the code. The code states that the output pin is PWM 3 for an ATmega328 which I use, but the sound from this pin is SUPER soft and noisy when I amplify the sound with an amplifier chip.
- PWM 13 produces clean and loud sound, but putting filters and effects over the sound does not seem to work.
Does somebody know why this is the case? I would really like to use effects over the sounds. Because what is a synthesizer without awesome effects?!
Thanks in advance !!
