/* Control a fan installed in the roof depending on roof & room temperature 
 * If the temp above is higher than the one below and the room is not hotter than 22°C 
 * the fan activates. 
 * a simple dimmer control is included
 * 1mhz CLK
 * Temperatures are measured with 2 identical KTY Sensors 
 * connected to ADC 2 and 3
 */
#include <avr/io.h>
#include <avr/wdt.h>
#include <avr/eeprom.h>
#include <avr/interrupt.h>
#include <avr/pgmspace.h>
#include <util/delay.h> 

// Ports
#define ROOM_PIN PB4
#define ROOF_PIN PB3
#define FAN_OUT PB1   // which is OC0B and OC1A - low active
#define TEST_PIN PB0  // very simple serial output 
#define MAINS_PIN PB2 // gets sine wave from mains to synchronize the dimmer
// ADC
// if differential mode is chosen and roof is hotter than room, give a positive output
#define ROOF_ADC 2   // 0010
#define ROOM_ADC 3	 // 0011
#define DIFF_ADC 6   // 0110 mux setting

#define ROOMTEMPMAX 522

// globals
volatile uint8_t roomtemp,rooftemp,difftemp;
volatile uint8_t pwm,buf = 0;
register volatile uint8_t ticker asm("r9");
register volatile uint8_t cnt asm("r8");

/* Once again the multi channel ADC Readout and Restart Routine.
 * it examines the MUX setting, stores the corresponding value
 * and then switches to the next channel
 * The ISR ends with restarting the ADC
 * a little bit of averaging is done,too.
 * note that this routine will never fire if you miss to start the ADC 
 * once after initializing with the ADIE flag set.
 */
ISR(ADC_vect) {
uint8_t mux = ADMUX;

	switch (mux & 0x07) {
		case ROOM_ADC 	:  	roomtemp = (roomtemp + ADCH) >> 1;  // averaging
							ADMUX = (mux & 0xF0) | ROOF_ADC;
							break;	
		case ROOF_ADC	:  	rooftemp = (rooftemp + ADCH) >> 1;  // averaging
							ADMUX = (mux & 0xF0) | ROOM_ADC;
							break;	
//		case DIFF_ADC	:  	difftemp = (difftemp + ADC) >> 1;
//							ADMUX = (mux & 0xF0) | ROOM_ADC;
//							break;	
	    default			:	ADMUX = (mux & 0xF0) | ROOM_ADC;
							break;	
   	}
ADCSRA = (1<<ADEN)|(1<<ADSC)|(0<<ADATE)|(1<<ADIF)|(1<<ADIE)|(1<<ADPS2);
}
/* mains ticker and serial output
 * initiated by filling buf with the char to send and cnt with the number of bits
 * 9 including startbit 
 * here we have a 10ms isr resulting in a baudrate of 100. 
 */

ISR(PCINT0_vect) {
 	TCNT1 = 0;			// reset dimmer pwm
//	OCR1A = 156-pwm;
 	PORTB |= (1<<FAN_OUT); // dimmer off
 	ticker++;
// very simple state machine for serial output with start and stop bit
	switch (cnt) {
		case 0 : PORTB |= (1<<TEST_PIN);  // stop bit high
				 break;
		case 9 : PORTB &= ~(1<<TEST_PIN); // startbit low
				 cnt--;
				 break;
		default : if (buf & 0x80) PORTB |=(1<<TEST_PIN); // shift out buf to pin
						else PORTB &= ~(1<<TEST_PIN);
						cnt--;      // one less bit to send
						buf <<= 1;  // msb first
						break;
			}
}
/* Timer 1 Overflow should never be reached except when the mains signal fails
 * switches off the triac 
 */
ISR(TIMER1_OVF_vect) {
	PORTB |= (1<<FAN_OUT);
	ticker++;
}
// On OC event give a pulse to the phototriac
ISR(TIM1_COMPA_vect) {
    PORTB &= ~(1<<FAN_OUT);
}

/* nonblocking serial sender */
void uart_put(uint8_t data) {
	if (cnt > 0) return; // transmission in progress
	buf = data;
	cnt=9;  // 9 bits to send - this includes the start bit
}

/* Init routines */
// initiate the ADC to start a single conversion with IRQ enabled
void initADC(void) {
	DIDR0 = (1<<ROOM_PIN)|(1<<ROOF_PIN);
	ADCSRA = (1<<ADEN)|(0<<ADATE)|(1<<ADIF)|(0<<ADIE)|(1<<ADPS2);
	ADCSRB = 0;
	ADMUX = (1<<ADLAR) | ROOM_ADC;
// start the first conversion
	ADCSRA = (1<<ADEN)|(1<<ADSC)|(0<<ADATE)|(1<<ADIF)|(1<<ADIE)|(1<<ADPS2);
}
// includes Pinchange IRQ enabling
void initPorts(void) {
	PORTB = 0;
	DDRB = (1<<FAN_OUT)|(1<<TEST_PIN);
	PORTB |= (1<<FAN_OUT);
	PCMSK = (1<<MAINS_PIN);
	GIFR = (1<<PCIF);
	GIMSK = (1<<PCIE);
}
// Fast PWM mode inverted output
// 1MHz/157/32 = 99 Hz PWM
void initTimers(void) {
	TCNT1 = 0;
	OCR1C = 159;
	OCR1A = 78;
	TCCR1 = (1<<CTC1)|(0<<PWM1A)|(0<<COM1A1)|(1<<CS12)|(1<<CS11)|(1<<CS10);
	TIMSK = (1<<TOIE1) | (1<<OCIE1A);
	TIFR = (1<<TOV1)|(1<<OCF1A); //clr pending
}
/* Synchronize OCR updates */
void waitfornextTimer(void) {
	while (ticker < 50) {};
	ticker = 0;
}
int main(void) {
uint16_t calc = 0;
	pwm = ticker = 0;
	roomtemp = rooftemp = difftemp = 0;
	initPorts();
	initADC();
	initTimers();
	sei();
// main loop
	while (1) {
		waitfornextTimer();   // time ticker 
		// debug
		pwm = roomtemp; 
		uart_put(pwm);
		OCR1A = pwm;
	}
	return 0;
}