mirror of
https://github.com/RobTillaart/Arduino.git
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90 lines
1.6 KiB
C++
90 lines
1.6 KiB
C++
//
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// FILE: DHT12.cpp
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// AUTHOR: Rob Tillaart
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// VERSION: 0.1.1
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// PURPOSE: I2C library for DHT12 for Arduino.
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//
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// HISTORY:
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// 0.1.0: 2017-12-11 initial version
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// 0.1.1: 2017-12-19 added ESP8266 - issue #86
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// Verified by Viktor Balint
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//
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// Released to the public domain
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//
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#include <Wire.h>
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#include <DHT12.h>
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#define DHT12_ADDRESS ((uint8_t)0x5C)
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////////////////////////////////////////////////////////////////////
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//
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// PUBLIC
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//
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#ifdef ESP8266
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void DHT12::begin(uint8_t sda, uint8_t scl)
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{
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Wire.begin(sda, scl);
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}
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#endif
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void DHT12::begin()
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{
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Wire.begin();
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}
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int8_t DHT12::read()
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{
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// READ SENSOR
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int status = _readSensor();
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if (status < 0) return status;
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// CONVERT AND STORE
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humidity = bits[0] + bits[1] * 0.1;
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temperature = (bits[2] & 0x7F) + bits[3] * 0.1;
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if (bits[2] & 0x80)
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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 checksum = bits[0] + bits[1] + bits[2] + bits[3];
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if (bits[4] != checksum)
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{
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return DHT12_ERROR_CHECKSUM;
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}
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return DHT12_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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// negative is error in communication
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// 5 is OK
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// 0..4 is too few bytes.
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int DHT12::_readSensor()
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{
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// GET CONNECTION
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Wire.beginTransmission(DHT12_ADDRESS);
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Wire.write(0);
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int rv = Wire.endTransmission();
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if (rv < 0) return rv;
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// GET DATA
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const uint8_t length = 5;
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int bytes = Wire.requestFrom(DHT12_ADDRESS, length);
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if (bytes == 0) return DHT12_ERROR_CONNECT;
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if (bytes < length) return DHT12_MISSING_BYTES;
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for (int i = 0; i < bytes; i++)
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{
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bits[i] = Wire.read();
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}
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return bytes;
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}
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// END OF FILE
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