OrangePi 相关·DHT11温度湿度传感器

引脚

略

算法实现

#include 
#include 
#include 
#include 
#define MAXTIMINGS      85
#define DHTPIN    19
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( "OringPi one wiringPi DHT11 Temperature test program\n" );

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

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

    return(0);
}

//第一次读取数据会出现无法读取