//  FullColorLED
//  2011.12.3. Toshi Nagata

//  D2,D5,D8,D11: R with 220 ohm
//  D3,D6,D9,D12: G with 100 ohm
//  D4,D7,D10,D13: B with 100 ohm
//  Cathode -> GND

#define PMAX 2048

//  Color change
//  Walk on the surface {x=1,y>=0,z>=0}, {x>=0,y=1,z>=0}, {x>=0,y>=0,z=1}
unsigned char colors[12] = {255, 0, 0, 0, 0, 255, 255, 0, 0, 0, 0, 255};
signed char dcol[12] = {0, 1, 3, 1, 3, 0, 2, 6, 0, 0, 1, 3};
unsigned char pwm[12] = {255, 0, 0, 0, 0, 255, 255, 0, 0, 0, 0, 255};
//  Brightness change
//  Linear back-and-forth move between -PMAX to PMAX*2, and 
//  limit the qunatity within [0, PMAX]
short pulser[4] = {-PMAX, -PMAX, -PMAX, -PMAX};
signed char dpulser[4] = {7, 11, 4, 2};

//  Timer for PWM output
//  Output i is 0 when timer >= pwm[i], 1 otherwise
unsigned char timer = 0;

//  Scaler for color change
unsigned char scaler = 0;

//  Table for converting amplitude to PWM strength
//  (to make brightness change smoother)
unsigned char table[256] = {
  0,1,1,2,2,3,4,4,5,5,6,7,7,8,8,9,
  10,10,11,12,12,13,13,14,15,15,16,17,17,18,19,19,
  20,21,21,22,23,23,24,25,25,26,27,27,28,29,29,30,
  31,32,32,33,34,34,35,36,37,37,38,39,39,40,41,42,
  42,43,44,45,45,46,47,48,48,49,50,51,52,52,53,54,
  55,56,56,57,58,59,60,60,61,62,63,64,65,65,66,67,
  68,69,70,70,71,72,73,74,75,76,77,77,78,79,80,81,
  82,83,84,85,85,86,87,88,89,90,91,92,93,94,95,96,
  97,98,99,100,101,102,103,104,105,106,107,108,109,110,111,112,
  113,114,115,116,117,118,119,120,121,122,123,124,125,126,127,128,
  129,131,132,133,134,135,136,137,138,139,141,142,143,144,145,146,
  147,149,150,151,152,153,154,156,157,158,159,160,162,163,164,165,
  166,168,169,170,171,173,174,175,177,178,179,180,182,183,184,186,
  187,188,189,191,192,193,195,196,197,199,200,202,203,204,206,207,
  208,210,211,213,214,216,217,218,220,221,223,224,226,227,229,230,
  232,233,235,236,238,239,241,242,244,245,247,248,250,251,253,255,
};

void setup()
{
  DDRD |= B11111100;  //  PD2-PD7 for output
  DDRB |= B00111111;  //  PB0-PB5 for output

  //  Set up Timer 2
  //  Disable overflow interrupt
  TIMSK2 &= ~(1<<TOIE2);
  //  WGM20/21/22 = 0 ... normal timer mode (not CTC, not PWM)
  TCCR2A &= ~((1<<WGM21) | (1<<WGM20));
  TCCR2B &= ~(1<<WGM22);
  //  Clock source = IO clock
  ASSR &= ~(1<<AS2);
  //  Disable compare match A interrupt
  TIMSK2 &= ~(1<<OCIE2A);
  //  prescale x8
  TCCR2B |= ((1<<CS20));
  TCCR2B &= ~((1<<CS22) | (1<<CS21));
  //  Reset and start timer interrupt
  TCNT2 = 0;
  TIMSK2 |= (1<<TOIE2);
}

//  Software PWM 12 channel
ISR(TIMER2_OVF_vect) {
  unsigned char i, m1;
  static const unsigned char mask[] = {4, 8, 16, 32, 64, 128, 1, 2, 4, 8, 16, 32};
  timer++;
  m1 = 0;
  for (i = 0; i < 6; i++) {
    if (pwm[i] > timer)
      m1 |= mask[i];
  }
  PORTD = m1;
  m1 = 0;
  for (i = 6; i < 12; i++) {
    if (pwm[i] > timer)
      m1 |= mask[i];
  }
  PORTB = m1;
}

void loop()
{
  short c;
  unsigned char m1;
  unsigned char i, j = 0;
  scaler++;
  if (scaler == 28) {
    scaler = 0;
    for (i = 0; i < 12; i++) {
      c = (short)colors[i] + (short)dcol[i];
      if (c < 0) {
        c = -c;
        dcol[i] = -dcol[i];
      } else if (c > 255) {
        c = 255;
        m1 = -dcol[i];
        dcol[i] = 0;
        i -= j;
        if (dcol[i] == 0) {
          dcol[i] = m1;
        } else if (dcol[i + 1] == 0) {
          dcol[i + 1] = m1;
        } else {
          dcol[i + 2] = m1;
        }
        i += j;
      }
      colors[i] = c;
      j++;
      if (j == 3)
        j = 0;
    }
  }
  for (i = 0; i < 4; i++) {
    c = pulser[i] + dpulser[i];
    if (c > PMAX * 2 || c < -PMAX) {
      dpulser[i] = -dpulser[i];
    }
    pulser[i] = c;
    if (c < 0)
      c = 0;
    else if (c > PMAX)
      c = PMAX;
    c /= (PMAX / 128);
    for (j = 0; j < 3; j++) {
      pwm[i * 3 + j] = table[((short)colors[i * 3 + j] * c) / 128];
    }
  }
}