//modified from https://github.com/pololu/pololu-led-strip-avr

#define F_CPU 16000000

#define LED_STRIP_PORT PORTD
#define LED_STRIP_DDR  DDRD
#define LED_STRIP_PIN  6

#include <avr/io.h>
#include <avr/interrupt.h>
#include <util/delay.h>
#include <stdint.h>

typedef struct ACRGB{
  uint8_t red, green, blue;
} ACRGB;

void __attribute__((noinline)) writeLeds(ACRGB * colors, uint16_t count){
  LED_STRIP_PORT &= ~(1<<LED_STRIP_PIN);
  LED_STRIP_DDR |= (1<<LED_STRIP_PIN);

  cli();   
  while (count--)
  {
    asm volatile (
        "ld __tmp_reg__, %a0+\n"
        "ld __tmp_reg__, %a0\n"
        "rcall send_led_strip_byte%=\n" 
        "ld __tmp_reg__, -%a0\n"
        "rcall send_led_strip_byte%=\n"  
        "ld __tmp_reg__, %a0+\n"
        "ld __tmp_reg__, %a0+\n"
        "ld __tmp_reg__, %a0+\n"
        "rcall send_led_strip_byte%=\n"  
        "rjmp led_strip_asm_end%=\n"     
        "send_led_strip_byte%=:\n"
        "rcall send_led_strip_bit%=\n"  
        "rcall send_led_strip_bit%=\n"
        "rcall send_led_strip_bit%=\n"
        "rcall send_led_strip_bit%=\n"
        "rcall send_led_strip_bit%=\n"
        "rcall send_led_strip_bit%=\n"
        "rcall send_led_strip_bit%=\n"
        "rcall send_led_strip_bit%=\n"  
        "ret\n"
        "send_led_strip_bit%=:\n"
#if F_CPU == 8000000
        "rol __tmp_reg__\n"                      
#endif
        "sbi %2, %3\n"                           

#if F_CPU != 8000000
        "rol __tmp_reg__\n"                      
#endif

#if F_CPU == 16000000
        "nop\n" "nop\n"
#elif F_CPU == 20000000
        "nop\n" "nop\n" "nop\n" "nop\n"
#elif F_CPU != 8000000
#error "Unsupported F_CPU"
#endif

        "brcs .+2\n" "cbi %2, %3\n"             

#if F_CPU == 8000000
        "nop\n" "nop\n"
#elif F_CPU == 16000000
        "nop\n" "nop\n" "nop\n" "nop\n" "nop\n"
#elif F_CPU == 20000000
        "nop\n" "nop\n" "nop\n" "nop\n" "nop\n"
        "nop\n" "nop\n"
#endif

        "brcc .+2\n" "cbi %2, %3\n"              

        "ret\n"
        "led_strip_asm_end%=: "
        : "=b" (colors)
        : "0" (colors),         
          "I" (_SFR_IO_ADDR(LED_STRIP_PORT)),   
          "I" (LED_STRIP_PIN)     
    );
  }
  sei();          
  _delay_us(80);  
}

uint8_t R,G,B;

double fmap(double x, double in_min, double in_max, double out_min, double out_max) {
  return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;
}

void HSVtoRGB(float H, float S,float V){
    H = fmap(H, 0, 255, 0, 360);
    S = fmap(S, 0, 255, 0, 100);
    V = fmap(V, 0, 255, 0, 100);
    if(H>360 || H<0 || S>100 || S<0 || V>100 || V<0){
        return;
    }
    float s = S/100;
    float v = V/100;
    float C = s*v;
    float X = C*(1-abs(fmod(H/60.0, 2)-1));
    float m = v-C;
    float r,g,b;
    if(H >= 0 && H < 60){
        r = C,g = X,b = 0;
    }
    else if(H >= 60 && H < 120){
        r = X,g = C,b = 0;
    }
    else if(H >= 120 && H < 180){
        r = 0,g = C,b = X;
    }
    else if(H >= 180 && H < 240){
        r = 0,g = X,b = C;
    }
    else if(H >= 240 && H < 300){
        r = X,g = 0,b = C;
    }
    else{
        r = C,g = 0,b = X;
    }
    R = (r+m)*255;
    G = (g+m)*255;
    B = (b+m)*255;
}

#define NUM_LEDS 60
ACRGB leds[NUM_LEDS];
uint8_t hue = 0;

int main(){
  while (1){
    for (uint16_t i = 0; i < NUM_LEDS; i++){
      HSVtoRGB(hue, 255, 255);
      leds[i] = {R,G,B};
    }

    writeLeds(leds, NUM_LEDS);
    hue++;
    _delay_ms(5);
  }
}