advent.c

/* -----------------------------------------------------------------------
 * Title:    advent.c
 *           Flicker 4 LEDs
 *           
 * Author:   Alexander Weber
 *           http://tinkerlog.com
 * Date:     22.11.2009
 * Hardware: ATtiny13v
 * Software: CrossPack-AVR-20090415
 *
 * Credits:
 * This code is based heavily on sritesmods version.
 * Find the original at http://spritesmods.com/?art=minimalism&f=gpl
 *
 * Changes:
 * - support 4 LEDs
 * - added a bit of sampling for light detection
 * - moved the "power down" out of the ISR, was always resetting
 * - removed callibration, replaced by hardwired value.
 */


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


#define LED1  PB4 
#define LED2  PB3
#define LED3  PB2
#define LED4  PB1
#define ADC2 2
#define AMBIENT_LIGHT 300

#define TRUE 1
#define FALSE 0


//Bunch o' random numbers: I'm too lazy to write or port a real random number
//generator.
//generated using bash:
//for x in `seq 0 255`; do echo -n $(($RANDOM%256)),; done
uint8_t const randomvals[] PROGMEM = {
 234,191,103,250,144,74,39,34,215,128,9,122,144,74,137,105,123,218,158,175,205,
 118,149,13,98,7,173,179,194,97,115,110,213,80,220,142,102,102,36,152,90,135,
 105,176,173,49,6,197,48,140,176,122,4,53,83,216,212,202,170,180,214,53,161,
 225,129,185,106,22,12,190,97,158,170,92,160,194,134,169,98,246,128,195,24,
 198,165,156,77,126,113,136,58,156,196,136,41,246,164,84,138,171,184,42,214,
 203,128,89,39,198,85,140,148,149,36,215,78,170,234,131,124,152,239,154,214,
 130,194,49,3,69,248,120,179,101,163,131,124,184,148,213,118,213,81,177,149,
 58,213,33,201,63,10,195,215,190,7,86,245,128,9,8,40,102,51,125,94,92,5,159,
 75,253,158,40,4,6,178,241,92,124,73,248,1,157,61,50,86,136,113,22,16,171,209,
 230,144,240,14,188,2,167,22,88,57,50,86,171,73,114,175,34,226,245,57,180,111,
 220,186,170,242,141,229,49,158,30,82,161,49,124,65,139,24,95,14,133,65,238,
 116,180,190,49,130,30,30,59,93,173,139,19,187,2,163,102,26,255,23,239,196,19,
 6,162
};

uint8_t mode_ee EEMEM = 0;                      // stores the mode in eeprom
static volatile uint8_t sleep = 0;

// Gets a semi-random number between 0 and 255
uint8_t getRandom(void) {
  //This'll probably give a warning because we use it uninitialised. Little 
  //does the compiler know: that's actually what we _want_ :)
  static uint8_t random1, random2;
  random1++;
  if (random1 == 0) {
    random2 += 0x41;
  }
  return pgm_read_byte(randomvals + random1) ^ random2;
}


uint16_t getLight(void) {
  uint16_t val = 0;
  uint8_t i;

  // measure pb4 using internal ref
  ADMUX = (1 << REFS0) | ADC2;             
  
  // enable ADC, prescaler 8
  ADCSRA = (1 << ADEN) | 3;
  
  // kill all leds
  PORTB &= ~((1 << LED1) | (1 << LED2) | (1 << LED3) | (1 << LED4));
  _delay_ms(5);

  // let led generate some voltage
  DDRB &= ~(1 << LED1);
  _delay_ms(5);

  // warm up the ADC, discard the first conversion
  ADCSRA |= (1 << ADSC);
  while (ADCSRA & (1 << ADSC)); 
  
  for (i = 0; i < 4; i++) {
    _delay_ms(5);
    ADCSRA |= (1 << ADSC);
    while (ADCSRA & (1 << ADSC)); 
    val += ADC;
  }
  val >>= 2;
  
  ADCSRA = 0;             // disable adc
  DDRB |= (1 << LED1);    // re-enable led

  return val;
}


void powerDown(void) {
  // Go to sleep until we're woken up by the wdt.
}


ISR(WDT_vect) {
  //check if it's still dark
  sleep = (getLight() > AMBIENT_LIGHT) ? TRUE : FALSE;
}

int main(void) {
  uint8_t lval1, lval2, lval3, lval4;
  uint8_t i, x, y;
  uint8_t mode;

  // set up wdt
  wdt_enable(WDTO_2S);


  WDTCR |= 0x40; // WDT generates interrupts instead of resets now.
                 // We want interrupts because a reset clears our nice random
                 // seeds, and an interrupt doesn't.
     
  for (i = 0; i < 10; i++) {
    _delay_ms(100);
  }

  // retrieve mode from eeprom and write back mode + 1
  mode = eeprom_read_byte(&mode_ee);
  mode = mode % 4;
  eeprom_write_byte(&mode_ee, mode + 1);  

  sei();

  // go directly into sleep mode and lets wake up by the wdt
  sleep = TRUE;

  // enable leds
  DDRB = (1 << LED1) | (1 << LED2) | (1 << LED3) | (1 << LED4);

  while (1) {

    WDTCR |= 0x40; // make sure wdt keeps generating an int instead of a reset

    if (sleep) {
      // switch off all LEDs and power down
      PORTB &= ~((1 << LED1) | (1 << LED2) | (1 << LED3) | (1 << LED4));
      set_sleep_mode(SLEEP_MODE_PWR_DOWN);
      sleep_mode();
    }
    else {
      // get a random value for the leds intensity
      lval1 = getRandom();
      lval2 = getRandom();
      lval3 = getRandom();
      lval4 = getRandom();    
      // Manually do some pwm
      for (x = 0; x < 20; x++) {
  if (mode == 0) {
    PORTB |= (1 << LED1);
  }
  else if (mode == 1) {
    PORTB |= (1 << LED1) | (1 << LED2);
  }
  else if (mode == 2) {
    PORTB |= (1 << LED1) | (1 << LED2) | (1 << LED3);
  }
  else if (mode == 3) {
    PORTB |= (1 << LED1) | (1 << LED2) | (1 << LED3) | (1 << LED4);
  }
  for (y = 0; y != 255; y++) {
    if (y == lval1) {
      PORTB &= ~(1 << LED1);
    }
    if (y == lval2) {
      PORTB &= ~(1 << LED2);
    }
    if (y == lval3) {
      PORTB &= ~(1 << LED3);
    }
    if (y == lval4) {
      PORTB &= ~(1 << LED4);
    }
    _delay_us(5);
  }
      }
    }
  }
}