dht22.c

#include <wiringPi.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <stdbool.h>
#include "print_bits.c"

#define DHT_PIN 7
#define DHT_TIMEOUT 200

bool sleepUntil(int pin, uint8_t state){
  int counter = 0;
  while(digitalRead(pin) != state){
    counter++;
    delayMicroseconds(1);
    if(counter > DHT_TIMEOUT) return false;
  }
  return true;
}

void readData(){

    uint8_t data[5] = {0,0,0,0,0};

    // MCU says hello
    pinMode(DHT_PIN, OUTPUT);
    digitalWrite(DHT_PIN, HIGH);
    delay(10);
    digitalWrite(DHT_PIN, LOW);
    delay(18);
    digitalWrite(DHT_PIN, HIGH);
    delayMicroseconds(40);

    // DHT responds
    pinMode(DHT_PIN, INPUT);
    if(!sleepUntil(DHT_PIN, HIGH)) return;
    if(!sleepUntil(DHT_PIN, LOW)) return;

    // Read data
    int i;
    for(i=0; i<40; i++){

      // ~50us
      if(!sleepUntil(DHT_PIN, HIGH)) return;
      uint32_t t = micros();
      if(!sleepUntil(DHT_PIN, LOW)) return;

      // > ~40us then HIGH bit
      data[i / 8] <<= 1;
      if(micros() - t >= 68){
        data[i / 8] |= 1; // turn on current bit
      }
      //if(i > 0 && i % 8 == 0) printBits(&data[(i / 8)-1]);
    }

    //printBits(&data[0]);
    //printBits(&data[1]);
    //printBits(&data[2]);
    //printBits(&data[3]);
    //printBits(&data[4]);

    if(data[4] == (data[0] + data[1] + data[2] + data[3]) & 0xFF){
     printf("0: %i\n", data[0]);
     printf("1: %i\n", data[1]);
     printf("2: %i\n", data[2]);
     printf("3: %i\n", data[3]);
     printf("4: %i\n", data[4]);
    }

}

int main(int argc, const char* argv[]){
  wiringPiSetup();
  for(;;) {
    delay(1000);

    printf("Reading: \n");
    readData();
  }
}

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