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DHTStable.cpp
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DHTStable.cpp
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//
// FILE: DHTStable.cpp
// AUTHOR: Rob Tillaart
// VERSION: 1.1.2
// PURPOSE: DHT Temperature & Humidity Sensor library for Arduino
// URL: https://github.com/RobTillaart/DHTstable
//
// HISTORY: see CHANGELOG.md
#include "DHTStable.h"
/////////////////////////////////////////////////////
//
// PUBLIC
//
DHTStable::DHTStable()
{
reset();
}
void DHTStable::reset()
{
_temperature = 0.0;
_humidity = 0.0;
_disableIRQ = false;
}
// return values:
// DHTLIB_OK
// DHTLIB_ERROR_CHECKSUM
// DHTLIB_ERROR_TIMEOUT
int DHTStable::read11(uint8_t pin)
{
// READ VALUES
if (_disableIRQ) noInterrupts();
int rv = _readSensor(pin, DHTLIB_DHT11_WAKEUP);
if (_disableIRQ) interrupts();
if (rv != DHTLIB_OK)
{
_humidity = DHTLIB_INVALID_VALUE; // invalid value, or is NaN prefered?
_temperature = DHTLIB_INVALID_VALUE; // invalid value
return rv;
}
// CONVERT AND STORE
_humidity = _bits[0] + _bits[1] * 0.1;
_temperature = (_bits[2] & 0x7F) + _bits[3] * 0.1;
if (_bits[2] & 0x80) // negative temperature
{
_temperature = -_temperature;
}
// TEST CHECKSUM
uint8_t sum = _bits[0] + _bits[1] + _bits[2] + _bits[3];
if (_bits[4] != sum)
{
return DHTLIB_ERROR_CHECKSUM;
}
return DHTLIB_OK;
}
// return values:
// DHTLIB_OK
// DHTLIB_ERROR_CHECKSUM
// DHTLIB_ERROR_TIMEOUT
int DHTStable::read(uint8_t pin)
{
// READ VALUES
if (_disableIRQ) noInterrupts();
int rv = _readSensor(pin, DHTLIB_DHT_WAKEUP);
if (_disableIRQ) interrupts();
if (rv != DHTLIB_OK)
{
_humidity = DHTLIB_INVALID_VALUE; // NaN preferred?
_temperature = DHTLIB_INVALID_VALUE; // NaN preferred?
return rv; // propagate error value
}
// CONVERT AND STORE
_humidity = word(_bits[0], _bits[1]) * 0.1;
int16_t t = ((_bits[2] & 0x7F) * 256 + _bits[3]);
if (t == 0)
{
_temperature = 0.0; // prevent -0.0;
}
else
{
_temperature = t * 0.1;
if((_bits[2] & 0x80) == 0x80 )
{
_temperature = -_temperature;
}
}
// TEST CHECKSUM
uint8_t sum = _bits[0] + _bits[1] + _bits[2] + _bits[3];
if (_bits[4] != sum)
{
return DHTLIB_ERROR_CHECKSUM;
}
return DHTLIB_OK;
}
/////////////////////////////////////////////////////
//
// PRIVATE
//
// return values:
// DHTLIB_OK
// DHTLIB_ERROR_TIMEOUT
int DHTStable::_readSensor(uint8_t pin, uint8_t wakeupDelay)
{
// INIT BUFFERVAR TO RECEIVE DATA
uint8_t mask = 128;
uint8_t idx = 0;
// EMPTY BUFFER
for (uint8_t i = 0; i < 5; i++) _bits[i] = 0;
// REQUEST SAMPLE
pinMode(pin, OUTPUT);
digitalWrite(pin, LOW);
delay(wakeupDelay);
pinMode(pin, INPUT);
delayMicroseconds(40);
// GET ACKNOWLEDGE or TIMEOUT
uint16_t loopCnt = DHTLIB_TIMEOUT;
while(digitalRead(pin) == LOW)
{
if (--loopCnt == 0) return DHTLIB_ERROR_TIMEOUT;
}
loopCnt = DHTLIB_TIMEOUT;
while(digitalRead(pin) == HIGH)
{
if (--loopCnt == 0) return DHTLIB_ERROR_TIMEOUT;
}
// READ THE OUTPUT - 40 _bits => 5 BYTES
for (uint8_t i = 40; i != 0; i--)
{
loopCnt = DHTLIB_TIMEOUT;
while(digitalRead(pin) == LOW)
{
if (--loopCnt == 0) return DHTLIB_ERROR_TIMEOUT;
}
uint32_t t = micros();
loopCnt = DHTLIB_TIMEOUT;
while(digitalRead(pin) == HIGH)
{
if (--loopCnt == 0) return DHTLIB_ERROR_TIMEOUT;
}
if ((micros() - t) > 40)
{
_bits[idx] |= mask;
}
mask >>= 1;
if (mask == 0) // next byte?
{
mask = 128;
idx++;
}
}
return DHTLIB_OK;
}
// -- END OF FILE --