while(GPIO_READ_PIN(pin)) //wait sensor pull down
                      usleep(1);

#define GPIO_DIR_INPUT(g) *(gpio+((g)/10)) &= ~(7<<(((g)%10)*3))
#define GPIO_DIR_OUTPUT(g) *(gpio+((g)/10)) |=  (1<<(((g)%10)*3))
#define GPIO_READ_PIN(g) (*(gpio+13) & (1<<(g))) && 1
#define GPIO_SET_PIN(g) *(gpio+7) = 1<<g;
#define GPIO_CLEAR_PIN(g) *(gpio+10) = 1<<g;

uint64_t readDHT(int pin) {

  // Set GPIO pin to output
      GPIO_DIR_OUTPUT(pin);     // set pin output
      GPIO_CLEAR_PIN(pin);      // Set low
      usleep(10000);                // DHT22 needs min 1-10 ms to signal a startup
      GPIO_SET_PIN(pin);        // Take pin high
      usleep(40);

  /*------------------sensor response --------------------*/
      GPIO_DIR_INPUT(pin);      // set pin input
      usleep(80); //sensor pull low 80 us
      usleep(80); // sensor pull up 80 us
      while(GPIO_READ_PIN(pin)); // wait till sensor pull down (ready to transmit data)

   /*--------------------- begin transmit data ------------*/

  uint64_t measure = 0;   // store the 40 bits
  uint8_t i;

      // start to read 40 bits
      for (i = 0; i < 40; i++) {
          while(GPIO_READ_PIN(pin) == 0) // wait till sensor pull up (ready to transmit bit)
              usleep(1);

          usleep(40); //wait 40us if still high then bit = 1 else bit = 0 because output=1 still 70 us
          if (GPIO_READ_PIN(pin))
          {
              measure = measure | (1 << i);
              while(GPIO_READ_PIN(pin)) //wait sensor pull down
                  usleep(1);
          }
      }
  return measure;
}