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//
// FILE: dht.cpp
// AUTHOR: Rob Tillaart
// VERSION: 0.2.4
// PURPOSE: DHT Temperature & Humidity Sensor library for Arduino
// URL: https://github.com/RobTillaart/Arduino/tree/master/libraries/DHTstable
//
// HISTORY:
// 0.2.4 2018-04-03 add get-/setDisableIRQ(bool b)
// 0.2.3 2018-02-21 change #defines in const int to enforce return types.
// https://github.com/RobTillaart/Arduino/issues/94
// 0.2.2 2017-12-12 add support for AM23XX types more explicitly
// 0.2.1 2017-09-20 fix https://github.com/RobTillaart/Arduino/issues/80
// 0.2.0 2017-07-24 fix https://github.com/RobTillaart/Arduino/issues/31 + 33
// 0.1.13 fix negative temperature
// 0.1.12 support DHT33 and DHT44 initial version
// 0.1.11 renamed DHTLIB_TIMEOUT
// 0.1.10 optimized faster WAKEUP + TIMEOUT
// 0.1.09 optimize size: timeout check + use of mask
// 0.1.08 added formula for timeout based upon clockspeed
// 0.1.07 added support for DHT21
// 0.1.06 minimize footprint (2012-12-27)
// 0.1.05 fixed negative temperature bug (thanks to Roseman)
// 0.1.04 improved readability of code using DHTLIB_OK in code
// 0.1.03 added error values for temp and humidity when read failed
// 0.1.02 added error codes
// 0.1.01 added support for Arduino 1.0, fixed typos (31/12/2011)
// 0.1.0 by Rob Tillaart (01/04/2011)
//
// inspired by DHT11 library
//
// Released to the public domain
//
#include "dht.h"
/////////////////////////////////////////////////////
//
// PUBLIC
//
// return values:
// DHTLIB_OK
// DHTLIB_ERROR_CHECKSUM
// DHTLIB_ERROR_TIMEOUT
int dht::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 dht::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 prefered?
temperature = DHTLIB_INVALID_VALUE; // NaN prefered?
return rv; // propagate error value
}
// CONVERT AND STORE
humidity = word(bits[0], bits[1]) * 0.1;
temperature = word(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;
}
/////////////////////////////////////////////////////
//
// PRIVATE
//
// return values:
// DHTLIB_OK
// DHTLIB_ERROR_TIMEOUT
int dht::_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
//