169 lines
4.1 KiB
C++
169 lines
4.1 KiB
C++
//
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// FILE: dht.cpp
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// AUTHOR: Rob Tillaart
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// VERSION: 0.2.0
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// PURPOSE: DHT Temperature & Humidity Sensor library for Arduino
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// URL: https://github.com/RobTillaart/Arduino/tree/master/libraries/DHTstable
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//
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// HISTORY:
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// 0.2.1 2017-09-20 fix https://github.com/RobTillaart/Arduino/issues/80
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// 0.2.0 2017-07-24 fix https://github.com/RobTillaart/Arduino/issues/31 + 33
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// 0.1.13 fix negative temperature
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// 0.1.12 support DHT33 and DHT44 initial version
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// 0.1.11 renamed DHTLIB_TIMEOUT
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// 0.1.10 optimized faster WAKEUP + TIMEOUT
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// 0.1.09 optimize size: timeout check + use of mask
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// 0.1.08 added formula for timeout based upon clockspeed
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// 0.1.07 added support for DHT21
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// 0.1.06 minimize footprint (2012-12-27)
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// 0.1.05 fixed negative temperature bug (thanks to Roseman)
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// 0.1.04 improved readability of code using DHTLIB_OK in code
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// 0.1.03 added error values for temp and humidity when read failed
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// 0.1.02 added error codes
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// 0.1.01 added support for Arduino 1.0, fixed typos (31/12/2011)
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// 0.1.0 by Rob Tillaart (01/04/2011)
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//
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// inspired by DHT11 library
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//
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// Released to the public domain
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//
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#include "dht.h"
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/////////////////////////////////////////////////////
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//
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// PUBLIC
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//
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// return values:
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// DHTLIB_OK
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// DHTLIB_ERROR_CHECKSUM
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// DHTLIB_ERROR_TIMEOUT
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int dht::read11(uint8_t pin)
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{
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// READ VALUES
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int rv = _readSensor(pin, DHTLIB_DHT11_WAKEUP);
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if (rv != DHTLIB_OK)
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{
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humidity = DHTLIB_INVALID_VALUE; // invalid value, or is NaN prefered?
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temperature = DHTLIB_INVALID_VALUE; // invalid value
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return rv;
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}
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// CONVERT AND STORE
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humidity = bits[0]; // bits[1] == 0;
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temperature = bits[2]; // bits[3] == 0;
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// TEST CHECKSUM
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uint8_t sum = bits[0] + bits[1] + bits[2] + bits[3];
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if (bits[4] != sum)
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{
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return DHTLIB_ERROR_CHECKSUM;
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}
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return DHTLIB_OK;
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}
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// return values:
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// DHTLIB_OK
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// DHTLIB_ERROR_CHECKSUM
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// DHTLIB_ERROR_TIMEOUT
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int dht::read(uint8_t pin)
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{
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// READ VALUES
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int rv = _readSensor(pin, DHTLIB_DHT_WAKEUP);
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if (rv != DHTLIB_OK)
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{
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humidity = DHTLIB_INVALID_VALUE; // invalid value, or is NaN prefered?
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temperature = DHTLIB_INVALID_VALUE; // invalid value
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return rv; // propagate error value
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}
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// CONVERT AND STORE
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humidity = word(bits[0], bits[1]) * 0.1;
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temperature = word(bits[2] & 0x7F, bits[3]) * 0.1;
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if (bits[2] & 0x80) // negative temperature
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{
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temperature = -temperature;
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}
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// TEST CHECKSUM
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uint8_t sum = bits[0] + bits[1] + bits[2] + bits[3];
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if (bits[4] != sum)
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{
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return DHTLIB_ERROR_CHECKSUM;
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}
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return DHTLIB_OK;
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}
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/////////////////////////////////////////////////////
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//
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// PRIVATE
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//
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// return values:
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// DHTLIB_OK
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// DHTLIB_ERROR_TIMEOUT
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int dht::_readSensor(uint8_t pin, uint8_t wakeupDelay)
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{
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// INIT BUFFERVAR TO RECEIVE DATA
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uint8_t mask = 128;
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uint8_t idx = 0;
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// EMPTY BUFFER
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for (uint8_t i = 0; i < 5; i++) bits[i] = 0;
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// REQUEST SAMPLE
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pinMode(pin, OUTPUT);
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digitalWrite(pin, LOW);
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delay(wakeupDelay);
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pinMode(pin, INPUT);
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delayMicroseconds(40);
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// GET ACKNOWLEDGE or TIMEOUT
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uint16_t loopCnt = DHTLIB_TIMEOUT;
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while(digitalRead(pin) == LOW)
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{
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if (--loopCnt == 0) return DHTLIB_ERROR_TIMEOUT;
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}
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loopCnt = DHTLIB_TIMEOUT;
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while(digitalRead(pin) == HIGH)
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{
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if (--loopCnt == 0) return DHTLIB_ERROR_TIMEOUT;
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}
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// READ THE OUTPUT - 40 BITS => 5 BYTES
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for (uint8_t i = 40; i != 0; i--)
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{
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loopCnt = DHTLIB_TIMEOUT;
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while(digitalRead(pin) == LOW)
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{
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if (--loopCnt == 0) return DHTLIB_ERROR_TIMEOUT;
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}
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uint32_t t = micros();
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loopCnt = DHTLIB_TIMEOUT;
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while(digitalRead(pin) == HIGH)
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{
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if (--loopCnt == 0) return DHTLIB_ERROR_TIMEOUT;
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}
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if ((micros() - t) > 40)
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{
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bits[idx] |= mask;
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}
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mask >>= 1;
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if (mask == 0) // next byte?
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{
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mask = 128;
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idx++;
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}
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}
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return DHTLIB_OK;
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}
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//
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// END OF FILE
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//
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