#include "dht11.h"
#include <inttypes.h>
#include <avr/io.h>
#include <util/delay.h>
#include "defines.h"

int dht11_humidity;
int dht11_temperature;

int dht11_read(){

    // Init Timer1 for timekeeping
    TIMSK1=0; // no interrupt
    TCNT1 = 0; // start at 0
    TCCR1A = 0; // nothing to do w timer
    TCCR1B = _BV(CS11); // start w 1us tick 

// BUFFER TO RECEIVE
    uint8_t bits[5];
    uint8_t cnt = 7;
    uint8_t idx = 0;

    // EMPTY BUFFER
    for (int i=0; i< 5; i++) bits[i] = 0;
// REQUEST SAMPLE
    bitSet(DHT11_DDDR,DHT11_DBIT); //pinMode(pin, OUTPUT);
    bitSet(DHT11_DPORT,DHT11_DBIT); // digitalWrite(pin, HIGH);
    _delay_ms(30);
    bitClear(DHT11_DPORT,DHT11_DBIT); //digitalWrite(pin, LOW);
    _delay_ms(18);
    bitSet(DHT11_DPORT,DHT11_DBIT); // digitalWrite(pin, HIGH);
    _delay_us(20);
    bitClear(DHT11_DDDR,DHT11_DBIT); //pinMode(pin, INPUT);
    bitSet(DHT11_DPORT,DHT11_DBIT);

    // ACKNOWLEDGE or TIMEOUT
    unsigned int loopCnt = 10000;
    while( bitRead(DHT11_DPIN,DHT11_DBIT) == LOW)
	if (loopCnt-- == 0) return DHT11_ERROR_TIMEOUT2;

    loopCnt = 10000;
    while( bitRead(DHT11_DPIN,DHT11_DBIT) == HIGH)
	if (loopCnt-- == 0) return DHT11_ERROR_TIMEOUT2;

    // READ OUTPUT - 40 BITS => 5 BYTES or TIMEOUT
    for (int i=0; i<40; i++)
    {
	loopCnt = 10000;
	while(bitRead(DHT11_DPIN,DHT11_DBIT) == LOW)
	    if (loopCnt-- == 0) return DHT11_ERROR_TIMEOUT;

	unsigned long t = TCNT1;


	loopCnt = 10000;
	while(bitRead(DHT11_DPIN,DHT11_DBIT) == HIGH)
	    if (loopCnt-- == 0) return DHT11_ERROR_TIMEOUT;

	unsigned long t2 = TCNT1;

	if ((t2 - t) > 40) bits[idx] |= (1 << cnt);
	if (cnt == 0)   // next byte?
	{
	    cnt = 7;    // restart at MSB
	    idx++;      // next byte!
	}
	else cnt--;
    }

    // WRITE TO RIGHT VARS
        // as bits[1] and bits[3] are allways zero they are omitted in formulas.
    dht11_humidity    = bits[0]; 
    dht11_temperature = bits[2]; 

    uint8_t sum = bits[0] + bits[2];  

    if (bits[4] != sum) return DHT11_ERROR_CHECKSUM;
    return DHT11_OK;
}