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return; bug fixed #10

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return; bug fixed #10

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28 changes: 12 additions & 16 deletions DHT.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -37,11 +37,10 @@ void DHT::setup(uint8_t pin, DHT_MODEL_t model)
if ( model == AUTO_DETECT) {
DHT::model = DHT22;
readSensor();
if ( error == ERROR_TIMEOUT ) {
if ( error == ERROR_TIMEOUT )
DHT::model = DHT11;
// Warning: in case we auto detect a DHT11, you should wait at least 1000 msec
// before your first read request. Otherwise you will get a time out error.
}
}
}

Expand Down Expand Up @@ -108,15 +107,15 @@ const char *DHT::getStatusString() {

#endif

void DHT::readSensor()
bool DHT::readSensor()
{
// Make sure we don't poll the sensor too often
// - Max sample rate DHT11 is 1 Hz (duty cicle 1000 ms)
// - Max sample rate DHT22 is 0.5 Hz (duty cicle 2000 ms)
unsigned long startTime = millis();
if ( (unsigned long)(startTime - lastReadTime) < (model == DHT11 ? 999L : 1999L) ) {
return;
}
if ( (unsigned long)(startTime - lastReadTime) < (model == DHT11 ? 999L : 1999L) )
return false;

lastReadTime = startTime;

temperature = NAN;
Expand All @@ -126,13 +125,11 @@ void DHT::readSensor()

digitalWrite(pin, LOW); // Send start signal
pinMode(pin, OUTPUT);
if ( model == DHT11 ) {
if ( model == DHT11 )
delay(18);
}
else {
else
// This will fail for a DHT11 - that's how we can detect such a device
delayMicroseconds(800);
}

pinMode(pin, INPUT);
digitalWrite(pin, HIGH); // Switch bus to receive data
Expand All @@ -154,7 +151,7 @@ void DHT::readSensor()
age = (unsigned long)(micros() - startTime);
if ( age > 90 ) {
error = ERROR_TIMEOUT;
return;
return false;
}
}
while ( digitalRead(pin) == (i & 1) ? HIGH : LOW );
Expand All @@ -164,9 +161,8 @@ void DHT::readSensor()
data <<= 1;

// A zero max 30 usecs, a one at least 68 usecs.
if ( age > 30 ) {
if ( age > 30 )
data |= 1; // we got a one
}
}

switch ( i ) {
Expand All @@ -184,7 +180,7 @@ void DHT::readSensor()

if ( (byte)(((byte)rawHumidity) + (rawHumidity >> 8) + ((byte)rawTemperature) + (rawTemperature >> 8)) != data ) {
error = ERROR_CHECKSUM;
return;
return false;
}

// Store readings
Expand All @@ -196,11 +192,11 @@ void DHT::readSensor()
else {
humidity = rawHumidity * 0.1;

if ( rawTemperature & 0x8000 ) {
if ( rawTemperature & 0x8000 )
rawTemperature = -(int16_t)(rawTemperature & 0x7FFF);
}
temperature = ((int16_t)rawTemperature) * 0.1;
}

error = ERROR_NONE;
return true;
}
2 changes: 1 addition & 1 deletion DHT.h
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Original file line number Diff line number Diff line change
Expand Up @@ -80,7 +80,7 @@ class DHT
static float toCelsius(float fromFahrenheit) { return (fromFahrenheit - 32.0) / 1.8; };

protected:
void readSensor();
bool readSensor();

float temperature;
float humidity;
Expand Down