#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;
}