我正在使用 Raspberry pi3 和 DHT11 传感器进行温度监测项目。 我有以下引脚位置
VCC 到引脚号:2 接地引脚号:6 输出到 GPIO:BCM22 即引脚 15
我用过的代码:
public class WeatherStationActivity extends Activity {
private Handler mHandler = new Handler();
private TextView mTxtStatus;
private PeripheralManagerService service = new PeripheralManagerService();
private Gpio tempGpio;
private int i = 0;
int[] dht11_dat = {0, 0, 0, 0, 0};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Log.d("Weather station", "Started Weather Station");
setContentView(R.layout.activity_main);
mTxtStatus = (TextView) findViewById(R.id.txtStatus);
try {
tempGpio = service.openGpio("BCM22");
Handler handler = new Handler();
handler.postDelayed(new Runnable() {
@Override
public void run() {
if (i == 10) {
handler.removeCallbacks(this);
} else {
getTemp();
handler.postDelayed(this, 5000);
}
i++;
}
}, 5000);
} catch (Exception e) {
e.printStackTrace();
}
}
private void getTemp() {
boolean laststate = false;
try {
laststate = tempGpio.getValue();
} catch (IOException e) {
e.printStackTrace();
}
int j = 0;
final int MAXTIMINGS = 85;
dht11_dat[0] = dht11_dat[1] = dht11_dat[2] = dht11_dat[3] = dht11_dat[4] = 0;
try {
tempGpio.setDirection(Gpio.DIRECTION_OUT_INITIALLY_LOW);
// tempGpio.setActiveType(Gpio.ACTIVE_LOW);
tempGpio.setValue(false);
// Thread.sleep(18);
TimeUnit.MILLISECONDS.sleep(18);
// tempGpio.setActiveType(Gpio.ACTIVE_HIGH);
// tempGpio.setActiveType(Gpio.ACTIVE_HIGH);
tempGpio.setValue(true);
TimeUnit.MICROSECONDS.sleep(40);
tempGpio.setDirection(Gpio.DIRECTION_IN);
/* tempGpio.setActiveType(Gpio.ACTIVE_HIGH);
tempGpio.setValue(true);*/
// tempGpio.setValue(true);
StringBuilder value = new StringBuilder();
for (int i = 0; i < MAXTIMINGS; i++) {
int counter = 0;
while (tempGpio.getValue() == laststate) {
counter++;
TimeUnit.MICROSECONDS.sleep(1);
if (counter == 255) {
break;
}
}
laststate = tempGpio.getValue();
mTxtStatus.append("\nLast State of Sensor " + laststate);
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]);
Log.i("Logger", "temperature value readed: " + value.toString());
mTxtStatus.append("\nTemp " + value.toString());
} else {
mTxtStatus.append("\nNothing is working ");
Log.i("Logger", "Nothing is working ");
}
} catch (IOException e) {
e.printStackTrace();
} catch (InterruptedException e) {
e.printStackTrace();
} catch (Exception ex) {
ex.printStackTrace();
}
}
private boolean checkParity() {
return dht11_dat[4] == (dht11_dat[0] + dht11_dat[1] + dht11_dat[2] + dht11_dat[3] & 0xFF);
}
}
上面的代码输出的是“Nothing is working”。
有什么我可能做错的建议吗？
最佳答案
您无法从 DHT11 中读取数据将 Raspberry Pi 3 与 Android Things 结合使用，因为 DHT11 响应脉冲的持续时间为 26-28 us 至 70 us，但带有 AT GPIO 的 RP3 的最大频率约为 3kHz，这意味着约 300 us 的脉冲持续时间。查看 this 的答案问题。
关于android - 使用 Android Things 通过 DHT11 读取温度，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/44778869/