/* Name: main.c
 * Author: Toshi Nagata
 * Copyright: 2011 (c) Toshi Nagata
 * License: Modified BSD License
 *
 *  ATtiny2313V
 *  PB7, PB4, PB1: Blue with 100 ohm
 *  PB6, PB3, PB0: Green with 100 ohm
 *  PB5, PB2, (PD6): Red with 220 ohm
 *  Cathode -> GND
 */

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

#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[9] = {255, 255, 0, 0, 0, 255, 255, 0, 0};
signed char dcol[9] = {0, 1, 3, 1, 3, 0, 2, 5, 0};
volatile unsigned char pwm[9] = {255, 255, 0, 0, 0, 255, 255, 0, 0};

//  Brightness change
//  Linear back-and-forth move between -PMAX to PMAX*2, and 
//  limit the qunatity within [0, PMAX]
short pulser[3] = {-PMAX, -PMAX, -PMAX};
signed char dpulser[3] = {13, 11, 5};

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

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

//  Table for converting amplitude to PWM strength
//  (to make brightness change smoother)
PROGMEM prog_uchar 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()
{
  cli();  //  Disable interrupt

  DDRB = 0b11111111;  //  PB0-PB4 for output
  DDRD = 0b01111000;  //  PD3-PD6 for output

  //  Set up Timer
  //  Disable all timer interrupts
  TIMSK = 0b00000000;

  //  WGM0/1/2 = 0 ... normal timer mode (not CTC, not PWM)
  //  Clock source = IO clock, no prescale
  TCCR0A = 0b00000000;
  TCCR0B = 0b00000001;

  //  Reset and start timer interrupt for timer 0 overflow
  TCNT0 = 0;
  TIMSK = (1<<TOIE0);

  sei();  //  Enable interrupt
}

//  Software PWM 9 channels
ISR(TIMER0_OVF_vect) {
  unsigned char m1;
  timer++;
  m1 = 0;
  if (pwm[0] > timer)
    m1 |= 128;
  if (pwm[1] > timer)
    m1 |= 64;
  if (pwm[2] > timer)
    m1 |= 32;
  if (pwm[3] > timer)
    m1 |= 16;
  if (pwm[4] > timer)
    m1 |= 8;
  if (pwm[5] > timer)
    m1 |= 4;
  if (pwm[6] > timer)
    m1 |= 2;
  if (pwm[7] > timer)
    m1 |= 1;
  PORTB = m1;
  m1 = 0;
  if (pwm[8] > timer)
    m1 = 64;
  PORTD = m1;
}

void loop()
{
  int c;
  unsigned char i, j = 0;

  scaler++;
  if (scaler == 17) {
    scaler = 0;
    for (i = 0; i < 9; i++) {
      c = (int)colors[i] + (int)dcol[i];
      if (c < 0) {
        c = -c;
        dcol[i] = -dcol[i];
      } else if (c > 255) {
        signed char dc;
        c = 255;
        dc = -dcol[i];
        i -= j;
        if (dcol[i] == 0) {
          dcol[i] = dc;
        } else if (dcol[i + 1] == 0) {
          dcol[i + 1] = dc;
        } else {
          dcol[i + 2] = dc;
        }
        i += j;
        dcol[i] = 0;
      }
      colors[i] = c;
      j++;
      if (j == 3)
        j = 0;
    }
  }
  for (i = 0; i < 3; 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] = pgm_read_byte(table + ((int)colors[i * 3 + j] * c) / 128);
    }
  }
  _delay_ms(6);
}

int main()
{
  setup();
  while (1) {
    loop();
  }
  return 0; /* Not reached */
}