381 lines
7.6 KiB
C++
381 lines
7.6 KiB
C++
//
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// FILE: SHT31.cpp
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// AUTHOR: Rob Tillaart
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// VERSION: 0.5.1
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// DATE: 2019-02-08
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// PURPOSE: Arduino library for the SHT31 temperature and humidity sensor
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// https://www.adafruit.com/product/2857
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// URL: https://github.com/RobTillaart/SHT31
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#include "SHT31.h"
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// SUPPORTED COMMANDS - single shot mode only
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static constexpr uint16_t SHT31_READ_STATUS = 0xF32D;
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static constexpr uint16_t SHT31_CLEAR_STATUS = 0x3041;
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static constexpr uint16_t SHT31_SOFT_RESET = 0x30A2;
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static constexpr uint16_t SHT31_HARD_RESET = 0x0006;
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static constexpr uint16_t SHT31_MEASUREMENT_FAST = 0x2416; // page 10 datasheet
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static constexpr uint16_t SHT31_MEASUREMENT_SLOW = 0x2400; // no clock stretching
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static constexpr uint16_t SHT31_HEAT_ON = 0x306D;
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static constexpr uint16_t SHT31_HEAT_OFF = 0x3066;
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static constexpr uint32_t SHT31_HEATER_TIMEOUT = 180000UL; // milliseconds
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static constexpr uint16_t SHT31_GET_SERIAL_NUMBER = 0x3682; // no clock stretching
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SHT31::SHT31(uint8_t address, TwoWire *wire)
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{
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_address = address;
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_wire = wire;
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_lastRead = 0;
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_rawTemperature = 0;
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_rawHumidity = 0;
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_heatTimeout = 0;
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_heaterStart = 0;
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_heaterStop = 0;
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_heaterOn = false;
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_error = SHT31_OK;
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}
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bool SHT31::begin()
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{
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if ((_address != 0x44) && (_address != 0x45))
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{
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return false;
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}
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return reset();
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}
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bool SHT31::isConnected()
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{
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_wire->beginTransmission(_address);
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int rv = _wire->endTransmission();
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if (rv != 0) _error = SHT31_ERR_NOT_CONNECT;
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return (rv == 0);
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}
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uint8_t SHT31::getAddress()
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{
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return _address;
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}
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bool SHT31::read(bool fast)
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{
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if (writeCmd(fast ? SHT31_MEASUREMENT_FAST : SHT31_MEASUREMENT_SLOW) == false)
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{
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return false;
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}
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delay(fast ? 4 : 15); // table 4 datasheet
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return readData(fast);
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}
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/////////////////////////////////////////////////////////////////
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//
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// STATUS
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//
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#ifdef doc
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// bit - description
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// ==================
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// 15 Alert pending status
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// '0': no pending alerts
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// '1': at least one pending alert - default
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// 14 Reserved ‘0’
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// 13 Heater status
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// '0’ : Heater OFF - default
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// '1’ : Heater ON
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// 12 Reserved '0’
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// 11 Humidity tracking alert
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// '0’ : no alert - default
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// '1’ : alert
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// 10 Temp tracking alert
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// '0’ : no alert - default
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// '1’ : alert
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// 9:5 Reserved '00000’
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// 4 System reset detected
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// '0': no reset since last ‘clear status register’ command
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// '1': reset detected (hard or soft reset command or supply fail) - default
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// 3:2 Reserved ‘00’
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// 1 Command status
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// '0': last command executed successfully
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// '1': last command not processed. Invalid or failed checksum
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// 0 Write data checksum status
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// '0': checksum of last write correct
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// '1': checksum of last write transfer failed
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#endif
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uint16_t SHT31::readStatus()
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{
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uint8_t status[3] = { 0, 0, 0 };
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// page 13 datasheet
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if (writeCmd(SHT31_READ_STATUS) == false)
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{
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return 0xFFFF;
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}
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// 16 bit status + CRC
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if (readBytes(3, (uint8_t*) &status[0]) == false)
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{
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return 0xFFFF;
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}
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if (status[2] != crc8(status, 2))
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{
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_error = SHT31_ERR_CRC_STATUS;
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return 0xFFFF;
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}
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return (uint16_t) (status[0] << 8) + status[1];
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}
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// resets the following bits
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// 15 Alert pending status
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// 11 Humidity tracking alert
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// 10 Temp tracking alert
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// 4 System reset detected
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bool SHT31::clearStatus()
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{
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if (writeCmd(SHT31_CLEAR_STATUS) == false)
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{
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return false;
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}
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return true;
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}
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bool SHT31::reset(bool hard)
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{
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bool b = writeCmd(hard ? SHT31_HARD_RESET : SHT31_SOFT_RESET);
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if (b == false)
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{
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return false;
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}
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delay(1); // table 4 datasheet
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return true;
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}
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void SHT31::setHeatTimeout(uint8_t seconds)
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{
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_heatTimeout = seconds;
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if (_heatTimeout > 180) _heatTimeout = 180;
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}
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/////////////////////////////////////////////////////////////////
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//
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// HEATER
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//
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bool SHT31::heatOn()
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{
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if (isHeaterOn()) return true;
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if ((_heaterStop > 0) && (millis() - _heaterStop < SHT31_HEATER_TIMEOUT))
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{
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_error = SHT31_ERR_HEATER_COOLDOWN;
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return false;
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}
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if (writeCmd(SHT31_HEAT_ON) == false)
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{
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_error = SHT31_ERR_HEATER_ON;
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return false;
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}
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_heaterStart = millis();
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_heaterOn = true;
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return true;
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}
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bool SHT31::heatOff()
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{
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// always switch off the heater - ignore _heaterOn flag.
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if (writeCmd(SHT31_HEAT_OFF) == false)
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{
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_error = SHT31_ERR_HEATER_OFF; // can be serious!
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return false;
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}
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_heaterStop = millis();
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_heaterOn = false;
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return true;
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}
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bool SHT31::isHeaterOn()
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{
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if (_heaterOn == false)
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{
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return false;
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}
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// did not exceed time out
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if (millis() - _heaterStart < (_heatTimeout * 1000UL))
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{
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return true;
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}
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heatOff();
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return false;
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}
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/////////////////////////////////////////////////////////////////
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//
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// ASYNCHRONUOUS INTERFACE
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//
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bool SHT31::requestData()
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{
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if (writeCmd(SHT31_MEASUREMENT_SLOW) == false)
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{
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return false;
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}
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_lastRequest = millis();
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return true;
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}
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bool SHT31::dataReady()
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{
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return ((millis() - _lastRequest) > 15); // TODO MAGIC NR
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}
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bool SHT31::readData(bool fast)
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{
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uint8_t buffer[6];
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if (readBytes(6, (uint8_t*) &buffer[0]) == false)
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{
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return false;
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}
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if (!fast)
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{
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if (buffer[2] != crc8(buffer, 2))
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{
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_error = SHT31_ERR_CRC_TEMP;
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return false;
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}
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if (buffer[5] != crc8(buffer + 3, 2))
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{
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_error = SHT31_ERR_CRC_HUM;
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return false;
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}
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}
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_rawTemperature = (buffer[0] << 8) + buffer[1];
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_rawHumidity = (buffer[3] << 8) + buffer[4];
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_lastRead = millis();
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return true;
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}
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/////////////////////////////////////////////////////////////////
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//
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// MISC
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//
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int SHT31::getError()
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{
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int rv = _error;
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_error = SHT31_OK;
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return rv;
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}
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/**
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* See https://sensirion.com/media/documents/E5762713/63D103C2/Sensirion_electronic_identification_code_SHT3x.pdf
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*/
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bool SHT31::getSerialNumber(uint32_t &serial, bool fast) {
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if (writeCmd(SHT31_GET_SERIAL_NUMBER) == false) {
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return false;
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}
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delay(1);
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uint8_t buffer[6];
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if (readBytes(6, &buffer[0]) == false) {
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return false;
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}
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if (!fast) {
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if (buffer[2] != crc8(buffer, 2)) {
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_error = SHT31_ERR_SERIAL_NUMBER_CRC;
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return false;
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}
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if (buffer[5] != crc8(buffer + 3, 2)) {
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_error = SHT31_ERR_SERIAL_NUMBER_CRC;
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return false;
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}
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}
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serial = buffer[0];
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serial <<= 8;
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serial += buffer[1];
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serial <<= 8;
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serial += buffer[3];
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serial <<= 8;
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serial += buffer[4];
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return true;
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}
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/////////////////////////////////////////////////////////////////
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//
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// PROTECTED
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//
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uint8_t SHT31::crc8(const uint8_t *data, uint8_t len)
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{
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// CRC-8 formula from page 14 of SHT spec pdf
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const uint8_t POLY(0x31);
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uint8_t crc(0xFF);
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for (uint8_t j = len; j; --j)
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{
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crc ^= *data++;
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for (uint8_t i = 8; i; --i)
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{
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crc = (crc & 0x80) ? (crc << 1) ^ POLY : (crc << 1);
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}
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}
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return crc;
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}
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bool SHT31::writeCmd(uint16_t cmd)
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{
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_wire->beginTransmission(_address);
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_wire->write(cmd >> 8 );
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_wire->write(cmd & 0xFF);
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if (_wire->endTransmission() != 0)
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{
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_error = SHT31_ERR_WRITECMD;
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return false;
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}
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_error = SHT31_OK;
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return true;
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}
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bool SHT31::readBytes(uint8_t n, uint8_t *val)
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{
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int rv = _wire->requestFrom(_address, (uint8_t) n);
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if (rv == n)
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{
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for (uint8_t i = 0; i < n; i++)
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{
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val[i] = _wire->read();
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}
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_error = SHT31_OK;
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return true;
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}
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_error = SHT31_ERR_READBYTES;
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return false;
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}
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// -- END OF FILE --
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