/* Sinussignalerzeugung mittels DDS

Ausgabe von zwei Sinussignalen mit vaiabler Frequenz, Amplitude und Phase mittels PWM

Auflösung der Variablen

R(frequenz) : F_PWM / 2^16 = 62,5kHz / 65536 = 0,95367Hz
R(phase)    : 360° / 256 = 1,4° = 0,025 rad
R(amplitude): 1 / 256 = 0,39%

*/

#include <util/atomic.h>

#define F_PWM 62500L   // Hz
#define PRESCALER 1
#define TIMER_RELOAD ((F_CPU / ( PRESCALER * F_PWM) -1))    // Fast PWM
#define DELAY 20    // ms, Pause für Zwischenschritte im Demo 
#define LOOPS 1     // Anzahl Schleifen pro Modulationsdemo

// Variablen

volatile uint16_t frequenz;
volatile uint8_t amplitude, phase;

const int8_t sinus[256] PROGMEM = {
  0, 3, 6, 9, 12, 16, 19, 22, 25, 28, 31, 34, 37, 40, 43, 46, 49, 
  51, 54, 57, 60, 63, 65, 68, 71, 73, 76, 78, 81, 83, 85, 88, 90, 
  92, 94, 96, 98, 100, 102, 104, 106, 107, 109, 111, 112, 113, 115, 116, 117, 
  118, 120, 121, 122, 122, 123, 124, 125, 125, 126, 126, 126, 127, 127, 127, 127, 
  127, 127, 127, 126, 126, 126, 125, 125, 124, 123, 122, 122, 121, 120, 118, 117, 
  116, 115, 113, 112, 111, 109, 107, 106, 104, 102, 100, 98, 96, 94, 92, 90, 
  88, 85, 83, 81, 78, 76, 73, 71, 68, 65, 63, 60, 57, 54, 51, 49, 
  46, 43, 40, 37, 34, 31, 28, 25, 22, 19, 16, 12, 9, 6, 3, 0, 
  -3, -6, -9, -12, -16, -19, -22, -25, -28, -31, -34, -37, -40, -43, -46, -49, 
  -51, -54, -57, -60, -63, -65, -68, -71, -73, -76, -78, -81, -83, -85, -88, -90, 
  -92, -94, -96, -98, -100, -102, -104, -106, -107, -109, -111, -112, -113, -115, -116, -117, 
  -118, -120, -121, -122, -122, -123, -124, -125, -125, -126, -126, -126, -127, -127, -127, -127, 
  -127, -127, -127, -126, -126, -126, -125, -125, -124, -123, -122, -122, -121, -120, -118, -117, 
  -116, -115, -113, -112, -111, -109, -107, -106, -104, -102, -100, -98, -96, -94, -92, -90, 
  -88, -85, -83, -81, -78, -76, -73, -71, -68, -65, -63, -60, -57, -54, -51, -49, 
  -46, -43, -40, -37, -34, -31, -28, -25, -22, -19, -16, -12, -9, -6, -3, 
};

void setup(){

  pinMode(A0,INPUT);
  pinMode(11,OUTPUT);   // OCR1A
  pinMode(12,OUTPUT);   // OCR1B

  // Timer1 initialisieren
  // Mode 14, Fast PWM (ICR1), nichtinvertierte PWM, Prescaler 1
  // OCR1A, OCR1B aktiv
  TCCR1A  = (1<<COM1A1) | (1<<COM1B1) | (1<<WGM11);
  TCCR1B  = (1<<WGM13)  | (1<<WGM12)  | (1<<CS10);
  ICR1    = TIMER_RELOAD;
  OCR1A   = TIMER_RELOAD / 2;   // PWM Startwerte, zum statischen testen
  OCR1B   = TIMER_RELOAD / 4; 
  TIMSK1 |= (1 << ICIE1);      // Aktivieren des Timer-Reload Interrupts (ICR1)

  frequenz  = 256;
  phase     = 0;
  amplitude = 255;
}

void loop() {
  uint16_t i, j;
  
  // Demonstration der Parameter

  // Amplitudenmodulation
  for (i=0; i<LOOPS; i++) {
    for (j=0; j<256; j++) {
      amplitude = j;
      delay(DELAY);
    }
    for (j=255; j>0; j--) {
      amplitude = j;
      delay(DELAY);
    }
  }
  amplitude = 255;

  // Frequenzmodulation
  for (i=0; i<LOOPS; i++) {
    for (j=0; j<256; j++) {
    // atomarer Datenzugriff auf Variablen, welche auch in einer ISR verwendet werden
    // und größer als die CPU-Wortbreite sind    
      ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
        frequenz = 256+2*j;
      }
      delay(DELAY);
    }
    for (j=255; j>0; j--) {
      ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
        frequenz = 256+2*j;
      }
      delay(DELAY);
    }
  }
  ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
    frequenz = 256;
  }

  // Phasenmodulation von OCR1B
  for (i=0; i<LOOPS; i++) {
    for (j=0; j<256; j++) {
      phase = j;
      delay(DELAY);
    }
    for (j=255; j>0; j--) {
      phase = j;
      delay(DELAY);
    }
  }
  phase = 0;
}

// Interrupt für Timer 1, Frequenz F_PWM
// Nachladen der PWM

ISR(TIMER1_CAPT_vect) {        
  // Index für Sinustabelle, Festkommazahl, 8 Bit Vorkomma, 8 Bit Nachkomma
  static uint16_t i;    

  i += frequenz;
  OCR1A = 128+(((int8_t)pgm_read_byte(&sinus[i>>8])*(int16_t)amplitude)>>8);
  OCR1B = 128+(((int8_t)pgm_read_byte(&sinus[((i>>8)+phase) & 0xFF])*(int16_t)amplitude)>>8);  
}