DHT22 sensor在read method中需使用INPUT_PULLUP

Victor · November 26, 2021, 4:53pm

在3.0.11, 3.1.0的DHT.cpp中，DHT22 sensor似乎需要使用pinMode(_pin,INPUT_PULLUP);才能成功讀到正確的值，目前的程式是pinMode(_pin,INPUT);

ambiot/ambd_arduino/blob/fc5763bdb97156c4a2e211df9f392c10574c5588/Arduino_package/hardware/libraries/GPIO/DHT.cpp#L175

    
      
          uint32_t cycles[80];
          {
              // Turn off interrupts temporarily because the next sections are timing critical and we don't want any interruptions.
              InterruptLock lock;
          
          
    // End the start signal by setting data line high for 20 microseconds.
              digitalWrite(_pin, HIGH); 
              delayMicroseconds(20);
          
          
    // Now start reading the data line to get the value from the DHT sensor.
              pinMode(_pin,INPUT); 
              // Delay a bit to let sensor pull data line low.
              delayMicroseconds(10);
          
          
    // First expect a low signal for ~80 microseconds followed by a high signal for ~80 microseconds again.
              if (expectPulse(LOW) == 0) {
                  DEBUG_PRINTLN(F("Timeout waiting for start signal low pulse."));
                  _lastresult = false;
                  return _lastresult;
              }
              if (expectPulse(HIGH) == 0) {

xidameng · November 29, 2021, 2:03am

謝謝，請問您用的是哪一個開發板呢？

Victor · November 29, 2021, 2:40am

@xidameng BW16，我手上的DH22都是有接LED的，不是很確定是不是這個因素還是真的DHT22就得用PULLUP

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DHT22 sensor在read method中需使用INPUT_PULLUP

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