Ich versuche, mit pi4j Temperaturdaten von einem DHT11-Temperatursensor zu lesen. Ich habe den in c und python geschriebenen Code auf dieser Site befolgt:http: //www.uugear.com/portfolio/dht11- ... oder-Modul / Aber es funktioniert nicht. Wenn ich die Anweisung 'dht11Pin.getState ()' teste, befindet sie sich immer im Zustand HIGH und ändert sich nie. Stimmt etwas in meinem Code nicht?

Below ist mein Code:

import java.util.concurrent.TimeUnit;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import com.pi4j.component.ObserveableComponentBase;
import com.pi4j.io.gpio.GpioController;
import com.pi4j.io.gpio.GpioFactory;
import com.pi4j.io.gpio.GpioPinDigitalMultipurpose;
import com.pi4j.io.gpio.Pin;
import com.pi4j.io.gpio.PinMode;
import com.pi4j.io.gpio.PinPullResistance;
import com.pi4j.io.gpio.PinState;
import com.pi4j.io.gpio.RaspiPin;

public class DHT11 extends ObserveableComponentBase {

private static final Pin DEFAULT_PIN = RaspiPin.GPIO_04;
private static final int MAXTIMINGS = 85;
private int[] dht11_dat = { 0, 0, 0, 0, 0 };
private GpioPinDigitalMultipurpose dht11Pin;
private static final Logger LOGGER = LogManager.getLogger(DHT11.class
        .getName());

public DHT11() {
    final GpioController gpio = GpioFactory.getInstance();
    dht11Pin = gpio.provisionDigitalMultipurposePin(DEFAULT_PIN,
            PinMode.DIGITAL_INPUT, PinPullResistance.PULL_UP);
}

public DHT11(int pin) {
    final GpioController gpio = GpioFactory.getInstance();
    dht11Pin = gpio.provisionDigitalMultipurposePin(LibPins.getPin(pin),
            PinMode.DIGITAL_INPUT, PinPullResistance.PULL_UP);
}

public double getTemperature() {
    PinState laststate = PinState.HIGH;
    int j = 0;
    dht11_dat[0] = dht11_dat[1] = dht11_dat[2] = dht11_dat[3] = dht11_dat[4] = 0;
    StringBuilder value = new StringBuilder();
    try {

        dht11Pin.setMode(PinMode.DIGITAL_OUTPUT);
        dht11Pin.low();
        Thread.sleep(18);
        dht11Pin.high();
        TimeUnit.MICROSECONDS.sleep(40);
        dht11Pin.setMode(PinMode.DIGITAL_INPUT);

        for (int i = 0; i < MAXTIMINGS; i++) {
            int counter = 0;
            while (dht11Pin.getState() == laststate) {
                counter++;
                TimeUnit.MICROSECONDS.sleep(1);
                if (counter == 255) {
                    break;
                }
            }

            laststate = dht11Pin.getState();

            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
        if ((j >= 40) && checkParity()) {
            value.append(dht11_dat[2]).append(".").append(dht11_dat[3]);
            LOGGER.info("temperature value readed: " + value.toString());
        }

    } catch (InterruptedException e) {

        LOGGER.error("InterruptedException: " + e.getMessage(), e);
    }
    if (value.toString().isEmpty()) {
        value.append(-1);
    }
    return Double.parseDouble(value.toString());
}

private boolean checkParity() {
    return (dht11_dat[4] == ((dht11_dat[0] + dht11_dat[1] + dht11_dat[2] + dht11_dat[3]) & 0xFF));
}

}