#include <avr/io.h>
#include <avr/interrupt.h>
#include <stdlib.h>

/*
H:          der Farbton als Farbwinkel H auf dem Farbkreis (z. B. 0° = Rot, 120° = Grün, 240° = Blau) 
S:          die Sättigung S in Prozent (z. B. 0% = keine Farbe, 50% = ungesättigte Farbe, 100% = gesättigte, reine Farbe) 
V:          der Grauwert V als Prozentwert angegeben (z. B. 0% = keine Helligkeit, 100% = volle Helligkeit)

Skalierung der HSV Werte:
H:      0-255, 0=rot, 42=gelb, 85=grün, 128=türkis, 171=blau, 214=violett
S:      0-255, 0=weißtöne, 255=volle Farben
V:      0-255, 0=aus, 255=maximale Helligkeit

*/


#define     Ledport             PORTB    // RGB Led Port
#define     DDR_Ledport         DDRB
#define     DDR_Inputport       DDRC
#define     R_PIN               0      // R Ausgang
#define     G_PIN               1      // G
#define     B_PIN               2      // B
#define    INVERT        0      // Ausgang Low aktiv ?

#define    Time        1      // Statusbit für Farbwechsel



// Prototypen
void hsv_to_rgb (unsigned char h, unsigned char s, unsigned char v);

// Globale Variabeln (Timer ISR)
volatile unsigned char Red, Green, Blue;    // PWM Register
volatile unsigned char Flags;
  

//-------------------------------------------------------------------------------
//Hauptprogramm
//-------------------------------------------------------------------------------
int main(void)
{  unsigned char H,S,V;

  DDR_Ledport=255;

  H=0;
  S=255;
  V=255;              // HSV Startwerte: rot, volle Helligkeit
  hsv_to_rgb(H,S,V);        // HSV to RGB


  TCCR0=1;
  TIMSK = (1<<TOIE0);        // T0 Starten, Overflow Interrupt f/256
  sei();              // Enable Interrupts

  for(;;)
  {
    if (Flags&Time)
    {  Flags&=~Time;
      H++;
      hsv_to_rgb(H,S,V);
    }
  }
}

//-------------------------------------------------------------------------------
//HSV nach RGB konvertieren
//-------------------------------------------------------------------------------

void hsv_to_rgb (unsigned char h, unsigned char s, unsigned char v)
{
  unsigned char r,g,b, i, f;
  unsigned int p, q, t;

  if( s == 0 ) 
   {  r = g = b = v;
  }
  else
  {  i=h/43;
    f=h%43;
    p = (v * (255 - s))/256;
    q = (v * ((10710 - (s * f))/42))/256;
    t = (v * ((10710 - (s * (42 - f)))/42))/256;

    switch( i )
    {  case 0:
        r = v; g = t; b = p; break;
      case 1:
        r = q; g = v; b = p; break;
      case 2:
        r = p; g = v; b = t; break;
      case 3:
        r = p; g = q; b = v; break;      
      case 4:
        r = t; g = p; b = v; break;        
      case 5:
         r = v; g = p; b = q; break;
    }
  }

  cli();                                              // Kein Interrupt beim übernehmen der neuen Werte!
  Red=r, Green=g, Blue=b;      
  sei();
}

//-------------------------------------------------------------------------------
//Timer  0 Interrupt, f/256
//-------------------------------------------------------------------------------

SIGNAL (SIG_OVERFLOW0)
{  static unsigned char PWM_cnt;

#if (INVERT==1)
  if (PWM_cnt <Red)
    Ledport &=~(1 << R_PIN);
  else
    Ledport |= (1 << R_PIN);

  if (PWM_cnt <Green)
    Ledport &=~(1 << G_PIN);
  else
    Ledport |= (1 << G_PIN);

  if (PWM_cnt <Blue)
    Ledport &=~(1 << B_PIN);
  else
    Ledport |= (1 << B_PIN);
#else
  if (PWM_cnt <Red)
    Ledport |= (1 << R_PIN);
  else
    Ledport &=~(1 << R_PIN);

  if (PWM_cnt <Green)
    Ledport |= (1 << G_PIN);
  else
    Ledport &=~(1 << G_PIN);

  if (PWM_cnt <Blue)
    Ledport |= (1 << B_PIN);
  else
    Ledport &=~(1 << B_PIN);
#endif
  PWM_cnt++;
  if (PWM_cnt==0)
    Flags|=Time;
}