라즈베리파이3 B+ 온도 습도 센서 DHT22 동작코드

 

 

라즈베리파이3 B+ 온도 습도 센서 DHT22 동작코드 

 

라즈베리파이 모델이 바뀌면서 에러가 난 부분입니다. 기존 코드에서 수정해주는 부분은 

이렇게 한번 해보세요.

 

코드에서 57 라인을 `counter > 16` => `counter > 50` 이렇게 바꿔보세요.

라인 54~60 라인을 아래와 같이요.

 

/* 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 ) */
if ( counter > 50 ) /* <- !! here !! */
dht11_dat[j / 8] |= 1;
j++;
}

 

전체 잘 돌아가는 소스코드는 아래와 같습니다.

 

/*
 *      dht22.c:
 *	Simple test program to test the wiringPi functions
 *	Based on the existing dht11.c
 *	Amended by technion@lolware.net
 */

#include <wiringPi.h>

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <sys/types.h>
#include <unistd.h>

#define MAXTIMINGS 85
//static int DHTPIN = 21;
//static int DHTPIN = 7;

static int DHTPIN = 11;
static int dht22_dat[5] = {0,0,0,0,0};

static uint8_t sizecvt(const int read)
{
  /* digitalRead() and friends from wiringpi are defined as returning a value
  < 256. However, they are returned as int() types. This is a safety function */

  if (read > 255 || read < 0)
  {
    printf("Invalid data from wiringPi library\n");
    exit(EXIT_FAILURE);
  }
  return (uint8_t)read;
}

static int read_dht22_dat()
{
  uint8_t laststate = HIGH;
  uint8_t counter = 0;
  uint8_t j = 0, i;

  dht22_dat[0] = dht22_dat[1] = dht22_dat[2] = dht22_dat[3] = dht22_dat[4] = 0;

  // pull pin down for 18 milliseconds
  pinMode(DHTPIN, OUTPUT);
  digitalWrite(DHTPIN, HIGH);
  delay(10);
  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 (sizecvt(digitalRead(DHTPIN)) == laststate) {
      counter++;
      delayMicroseconds(1);
      if (counter == 255) {
        break;
      }
    }
    laststate = sizecvt(digitalRead(DHTPIN));

    if (counter == 255) break;

    // ignore first 3 transitions
    if ((i >= 4) && (i%2 == 0)) {
      // shove each bit into the storage bytes
      dht22_dat[j/8] <<= 1;
      if (counter > 50)
        dht22_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) && 
      (dht22_dat[4] == ((dht22_dat[0] + dht22_dat[1] + dht22_dat[2] + dht22_dat[3]) & 0xFF)) ) {
        float t, h;
        h = (float)dht22_dat[0] * 256 + (float)dht22_dat[1];
        h /= 10;
        t = (float)(dht22_dat[2] & 0x7F)* 256 + (float)dht22_dat[3];
        t /= 10.0;
        if ((dht22_dat[2] & 0x80) != 0)  t *= -1;


    printf("Humidity = %.2f %% Temperature = %.2f *C \n", h, t );
    return 1;
  }
  else
  {
    printf("Data not good, skip\n");
    return 0;
  }
}

//int main (int argc, char *argv[])
int main (void)
{
  int count = 0;
  //여기에서 온도와 습도를 읽어옵니다.
  if (wiringPiSetup() == -1)
    exit(EXIT_FAILURE) ;
	
  if (setuid(getuid()) < 0)
  {
    perror("Dropping privileges failed\n");
    exit(EXIT_FAILURE);
  }

  while(1){
  while (read_dht22_dat() == 0) 
  {
     delay(1000); // wait 1sec to refresh 1초간 기다립니다.
     printf(" count %d", count++); 
  }
  }


  return 0 ;
}

 

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