NanoPi M1 Plus - DHT11 온도 습도 측정

NanoPi M1 Plus - DHT11 온도 습도 측정

출처 : DHT11 Humidity & Temperature Sensor Module | UUGear

C 언어

/*
 *  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);
}

컴파일

# gcc -Wall -o dht11 dht11.c -lwiringPi -lpthread

실행

디버깅 모드 설정

# export WIRINGPI_DEBUG=TRUE

디버깅 모드 해지

# unset WIRINGPI_DEBUG

실행

# ./dht11     
Raspberry Pi wiringPi DHT11 Temperature test program
Data not good, skip
Humidity = 22.0 % Temperature = 23.0 *C (73.4 *F)
Humidity = 22.0 % Temperature = 23.0 *C (73.4 *F)
Data not good, skip
Data not good, skip
Humidity = 22.0 % Temperature = 23.0 *C (73.4 *F)