Jump to content
43oh

Auduino code


Recommended Posts

I am sure everybody has seen the Auduino code (Grain synth for arduino).  I don't really understand the way that the PWM is setup, so I have no idea how to make this work on the MSP430 (or if it even can).  Could someone explain how the timers are setup in this code? and the interrupt vector as well?  I am just curious how one would setup the timer on one of the MSP430's?

// Auduino, the Lo-Fi granular synthesiser
//
// by Peter Knight, Tinker.it http://tinker.it
//
// Help:      http://code.google.com/p/tinkerit/wiki/Auduino
// More help: http://groups.google.com/group/auduino
//
// Analog in 0: Grain 1 pitch
// Analog in 1: Grain 2 decay
// Analog in 2: Grain 1 decay
// Analog in 3: Grain 2 pitch
// Analog in 4: Grain repetition frequency
//
// Digital 3: Audio out (Digital 11 on ATmega8)
//
// Changelog:
// 19 Nov 2008: Added support for ATmega8 boards
// 21 Mar 2009: Added support for ATmega328 boards
// 7 Apr 2009: Fixed interrupt 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;
}

So really I would just like someone to explain:

 // Set up PWM to 31.25kHz, phase accurate
  TCCR2A = _BV(COM2B1) | _BV(WGM20);
  TCCR2B = _BV(CS20);
  TIMSK2 = _BV(TOIE2);

and these defines:

#define PWM_PIN       3
#define PWM_VALUE     OCR2B
#define PWM_INTERRUPT TIMER2_OVF_vect

and if there is a way to setup one of the timers on the 2452 or 2553 to accomplish the same thing.

 

 

As always, thanks very much.

 

L293D

 

Link to post
Share on other sites

Ok, so I have figured part of this out.  Now the only thing I can't figure out is why analogRead doesn't work when I am using an interrupt (CCIE) on TA0.  Is that because analogRead uses the same interrupt?  If so, does that just mean that I need to setup the ADC manually instead of using analogRead?

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...