62 lines
2.5 KiB
C++
62 lines
2.5 KiB
C++
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/*
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SHT21.cpp - SHT21 Sensor Library
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Copyright (c) 2019-2020, Stefan Brand
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All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are met:
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1. Redistributions of source code must retain the above copyright notice, this
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list of conditions and the following disclaimer.
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2. Redistributions in binary form must reproduce the above copyright notice,
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this list of conditions and the following disclaimer in the documentation
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and/or other materials provided with the distribution.
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3. Neither the name of the copyright holder nor the names of its
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contributors may be used to endorse or promote products derived from
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this software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <Arduino.h>
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#include <inttypes.h>
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#include <Wire.h>
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#include "SHT21.h"
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SHT21::SHT21() {}
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uint16_t SHT21::sensorRead(uint8_t command) {
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uint8_t d = 85; // Delay after starting Measurement
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if(command == SHT21_TEMPHOLD || command == SHT21_TEMPNOHOLD) d = 85;
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if(command == SHT21_HUMIHOLD || command == SHT21_HUMINOHOLD) d = 30;
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// Trigger Measurement
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Wire.beginTransmission(SHT21_I2CADDR);
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Wire.write(command);
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Wire.endTransmission();
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// Wait for Measurement
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delay(d);
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// Read and Return value
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Wire.requestFrom(SHT21_I2CADDR, 2);
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uint16_t result = (Wire.read() << 8) | Wire.read();
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result &= ~0x0003; // Clear CRC Bits
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return result;
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}
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float SHT21::getTemperature(void) {
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return (-46.85 + 175.72 / 65536.0 * (float)(sensorRead(SHT21_TEMPHOLD)));
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}
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float SHT21::getHumidity(void) {
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return (-6.0 + 125.0 / 65536.0 * (float)(sensorRead(SHT21_HUMIHOLD)));
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}
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