/*
 * dht11.c:
 *  Simple test program to test the wiringPi functions
 *  DHT11 test
 */

#include <wiringPi.h>

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#define MAXTIMINGS 85
#define DHTPIN 7
int dht11_dat[5] = {0,0,0,0,0};

void read_dht11_dat()
{
  uint8_t laststate = HIGH;
  uint8_t counter = 0;
  uint8_t j = 0, i;
  float f; // fahrenheit

  dht11_dat[0] = dht11_dat[1] = dht11_dat[2] = dht11_dat[3] = dht11_dat[4] = 0;

  // pull pin down for 18 milliseconds
  pinMode(DHTPIN, OUTPUT);
  digitalWrite(DHTPIN, LOW);
  delay(18);
  // then pull it up for 40 microseconds
  digitalWrite(DHTPIN, HIGH);
  delayMicroseconds(40); 
  // prepare to read the pin
  pinMode(DHTPIN, INPUT);

  // detect change and read data
  for ( i=0; i< MAXTIMINGS; i++) {
    counter = 0;
    while (digitalRead(DHTPIN) == laststate) {
      counter++;
      delayMicroseconds(1);
      if (counter == 255) {
        break;
      }
    }
    laststate = digitalRead(DHTPIN);

    if (counter == 255) break;

    // ignore first 3 transitions
    if ((i >= 4) && (i%2 == 0)) {
      // shove each bit into the storage bytes
      dht11_dat[j/8] <<= 1;
      if (counter > 16)
        dht11_dat[j/8] |= 1;
      j++;
    }
  }

  // check we read 40 bits (8bit x 5 ) + verify checksum in the last byte
  // print it out if data is good
  if ((j >= 40) && 
      (dht11_dat[4] == ((dht11_dat[0] + dht11_dat[1] + dht11_dat[2] + dht11_dat[3]) & 0xFF)) ) {
    f = dht11_dat[2] * 9. / 5. + 32;
    printf("Humidity = %d.%d %% Temperature = %d.%d *C (%.1f *F)\n", 
            dht11_dat[0], dht11_dat[1], dht11_dat[2], dht11_dat[3], f);
  }
  else
  {
    printf("Data not good, skip\n");
  }
}

int main (void)
{

  printf ("Raspberry Pi wiringPi DHT11 Temperature test program\n") ;

  if (wiringPiSetup () == -1)
    exit (1) ;

  while (1) 
  {
     read_dht11_dat();
     delay(1000); // wait 1sec to refresh
  }

  return 0 ;
}