Airfresher photo controller firmware for ATtiny10

airfresher.c

#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/pgmspace.h>
#include <avr/sleep.h>
#include <avr/wdt.h>
#include <stdint.h>

// Airfresher photo controller for an ATTiny 4/5/9/10
// by kramolnic

///////////////////////////////////////////////////////////////////////////////////////
// SETTINGS (you can change this values)

// Light time, sec:
#define LIGHT_SECS_TO_FIRE 150

// Dark time, sec:
#define  DARK_SECS_TO_FIRE 5

///////////////////////////////////////////////////////////////////////////////////////


//(Input) Light sensor is PB2 (PCINT2 / INT0) pin
#define LIGHT_SENSOR_PIN _BV(2)

//(Output) LED indicator
#define LED_PIN _BV(1)

//(Output) Drive control is PB0 (OC0A) pin
#define DRIVE_CONTROL_PIN _BV(0)



enum State
{
   s1 = 0, //Active mode - time counting
   s2      //Waiting for watchdog reset
};

volatile enum State state;
volatile uint32_t lightTimeCounter;
volatile uint32_t darkTimeCounter;

//Light sensor INT0 external interrupt (low-level async interrupt)
ISR (INT0_vect)
{
  asm("nop");
}

//Timer compare A match interrupt (one-second timer)
ISR (TIM0_COMPA_vect)
{   
   if (PINB & LIGHT_SENSOR_PIN) // dark 
   {
      PORTB ^= LED_PIN;

      darkTimeCounter++;
   }
   else // light
   {
      PORTB &= ~LED_PIN;

      lightTimeCounter++;
       darkTimeCounter = 0;
   }
}

int main()
{
   /////////////////////////////////////////////////////////////////////////////////////

   cli(); // Initialization begin

   // disable watchdog timer (activated once, still active after reset!)
   wdt_reset();
   RSTFLR &= ~(1<<WDRF);
   CCP = 0xD8;
   WDTCSR &= ~(1<<WDE);

   // disable Analog comparator (enabled by default)
   ACSR = (1<<ACD);

   // disable Voltage level monitor
   VLMCSR = 0;

   // configure output pins
   DDRB = DRIVE_CONTROL_PIN | LED_PIN;

   // configure INT0 interrupt from light sensor
   EICRA = (0<<ISC01) | (0<<ISC00); //Low level on INT0 generates an interrupt request
   EIMSK = (1<<INT0);               //Enable external INT0 from light sensor

   // configure timer (OCR0A = 500 = 0x01F4) => 1Hz timer
   OCR0AH = 0x01;
   OCR0AL = 0xF4;

   // reset counters and state
   state = s1;
   lightTimeCounter = 0;
    darkTimeCounter = 0;
  
   // Configure sleep mode
   set_sleep_mode(SLEEP_MODE_PWR_DOWN);

   // configure Main Clock Source to 500Hz
   CCP = 0xD8; 	    //Enable CCP.
   CLKMSR = (0<<CLKMS1) | (1<<CLKMS0);   //Internal 128 kHz Oscillator (WDT Oscillator)
   CCP = 0xD8;
   CLKPSR = (1<<CLKPS3) | (0<<CLKPS2) | (0<<CLKPS1) | (0<<CLKPS0); //500 Hz Main Clock operation (128 kHz / 256)

   sei(); // Initialization end

   /////////////////////////////////////////////////////////////////////////////////////

   // Enter Power-down mode
   sleep_enable();
   sleep_cpu();

   cli();

   EIMSK = (0<<INT0); //Disable external INT0

   sleep_disable();

   //activate timer
   TCCR0A = (0<<COM0A1) | (0<<COM0A0) | (0<<COM0B1) | (0<<COM0B0) | (0<<WGM01) | (0<<WGM00); //Toggle OC0B on compare match
   TCCR0B = (0<<ICNC0)  | (0<<ICES0)  | (0<<WGM03)  | (1<<WGM02)  | (0<<CS02)  | (0<<CS01) | (1<<CS00); //clkIO/1 (no prescaling) => 1Hz
   TIMSK0 = (1<<OCIE0A); // Output compare A match int enable

   set_sleep_mode(SLEEP_MODE_IDLE);

   sei();

   while(1)
   {
      sleep_enable();
      sleep_cpu();

      switch (state)
      {
      case s1:
      {
         if (darkTimeCounter > DARK_SECS_TO_FIRE)      // the light is off longer than DARK_SECS...
         {
	    if (lightTimeCounter > LIGHT_SECS_TO_FIRE) // the light was ON longer than LIGHT_SECS...
            {
		PORTB |= DRIVE_CONTROL_PIN; //enable drive
            }

	    // enable watchdog
            wdt_reset();
            wdt_enable(WDTO_1S);

            state = s2;
         }
      }
      break;

      case s2: //NOTE: nothing to do - waiting for watchdog reset
      break;
      }
   }
}