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DHTSensor fixes #1979

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merged 3 commits into from
Nov 9, 2019
Merged

DHTSensor fixes #1979

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bad2855
sensor/dht: increase the delay per DHT22 datasheet
mcspr Nov 8, 2019
6861417
sensor/dht: set pin mode before digitalWrite
mcspr Nov 8, 2019
d5ff0d3
sensor/dht: wait DHT_MIN_INTERVAL after initialization
mcspr Nov 8, 2019
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20 changes: 15 additions & 5 deletions code/espurna/sensors/DHTSensor.h
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Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,8 @@
#define DHT_CHIP_DHT21 21
#define DHT_CHIP_AM2301 21

#define DHT_DUMMY_VALUE -255

class DHTSensor : public BaseSensor {

public:
Expand Down Expand Up @@ -75,6 +77,9 @@ class DHTSensor : public BaseSensor {
}
_previous = _gpio;

// Set now to fail the check in _read at least once
_last_ok = millis();

_count = 2;
_ready = true;

Expand Down Expand Up @@ -126,7 +131,11 @@ class DHTSensor : public BaseSensor {
void _read() {

if ((_last_ok > 0) && (millis() - _last_ok < DHT_MIN_INTERVAL)) {
_error = SENSOR_ERROR_OK;
if ((_temperature == DHT_DUMMY_VALUE) && (_humidity == DHT_DUMMY_VALUE)) {
_error = SENSOR_ERROR_WARM_UP;
} else {
_error = SENSOR_ERROR_OK;
}
return;
}

Expand All @@ -137,19 +146,20 @@ class DHTSensor : public BaseSensor {
unsigned char byteInx = 0;
unsigned char bitInx = 7;

pinMode(_gpio, OUTPUT);

// Send start signal to DHT sensor
if (++_errors > DHT_MAX_ERRORS) {
_errors = 0;
digitalWrite(_gpio, HIGH);
nice_delay(250);
}
pinMode(_gpio, OUTPUT);
noInterrupts();
digitalWrite(_gpio, LOW);
if ((_type == DHT_CHIP_DHT11) || (_type == DHT_CHIP_DHT12)) {
nice_delay(20);
} else {
delayMicroseconds(500);
delayMicroseconds(1100);
}
digitalWrite(_gpio, HIGH);
delayMicroseconds(40);
Expand Down Expand Up @@ -245,8 +255,8 @@ class DHTSensor : public BaseSensor {
unsigned long _last_ok = 0;
unsigned char _errors = 0;

double _temperature = 0;
double _humidity = 0;
double _temperature = DHT_DUMMY_VALUE;
double _humidity = DHT_DUMMY_VALUE;

};

Expand Down