2021-01-29 06:31:58 -05:00
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[](https://github.com/marketplace/actions/arduino_ci)
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[](https://github.com/RobTillaart/SHT31/releases)
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[](https://github.com/RobTillaart/SHT31/blob/master/LICENSE)
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2020-11-27 05:33:55 -05:00
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# SHT31
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Arduino library for the SHT31 temperature and humidity sensor
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2021-01-29 06:31:58 -05:00
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## Description
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2020-11-27 05:33:55 -05:00
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The SHT3x family of sensors should work up to 1 MHz I2C
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This library should also work for SHT30 and SHT35 but these are
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not tested yet.
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| SENSOR | Temperature accuracy | Humidity accuracy |
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|:----:|:----:|:----:|
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| SHT30 | ~0.3 | 2 |
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| SHT31 | ~0.3 | 1.5 |
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| SHT35 | ~0.2 | 1.5 |
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An elaborated library for the SHT31 sensor can be found here
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https://github.com/hawesg/SHT31D_Particle_Photon_ClosedCube
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2021-01-29 06:31:58 -05:00
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## Interface
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#### Base interface
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- **SHT31()** constructor.
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- **begin(address, dataPin, clockPin)** begin function for ESP8266 & ESP32;
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returns false if device address is incorrect or device cannot be reset.
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- **begin(address)** for single I2C bus platforms, e.g UNO.
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- **begin(address, TwoWire \*wire)** for platforms with multiple I2C busses.
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- **read(bool fast = true)** blocks 4 (fast) or 15 (slow) milliseconds + actual read + math
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- **isConnected()** check sensor is reachable over I2C. Returns false if not connected.
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- **uint16_t readStatus()** details see datasheet and **Status fields** below
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- **uint32_t lastRead()** in milliSeconds since start of program.
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- **reset(bool hard = false)** resets the sensor, soft reset by default. Returns false if fails.
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- **getHumidity()** returns relative humidity in %
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- **getTemperature()** returns temperature in <20>C
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#### Error interface
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- **getError()** returns last set error flag and clear it.
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Be sure to clear the error flag by calling **getError()** before calling any command as the error flag could be from a previous command.
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| Error | Symbolic | Description |
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|:----:|:----|:----|
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| 0x00 | SHT31_OK | no error |
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| 0x81 | SHT31_ERR_WRITECMD | I2C write failed |
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| 0x82 | SHT31_ERR_READBYTES | I2C read failed |
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| 0x83 | SHT31_ERR_HEATER_OFF | Could not switch off heater |
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| 0x84 | SHT31_ERR_NOT_CONNECT | Could not connect |
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| 0x85 | SHT31_ERR_CRC_TEMP | CRC error in temperature |
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| 0x86 | SHT31_ERR_CRC_HUM | CRC error in humidity |
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| 0x87 | SHT31_ERR_CRC_STATUS | CRC error in statusfield |
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#### Heater interface
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Use the heater for max **180** seconds, and let it cool down an equal period of time.
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**WARNING:** Do not use heater for long periods.
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**WARNING:** The user is responsible to switch the heater off manually!
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The class does **NOT** do this automatically.
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- **setHeatTimeout(uint8_t seconds)** Set the time out of the heat cycle.
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This value is truncated to max 180 seconds.
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- **heatOn()** switches heat cycle on. Returns false if fails.
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- **heatOff()** switches heat cycle off. Returns false if fails.
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- **isHeaterOn()** is the sensor still in heating cycle? replaces **heatUp()**.
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Will switch heat off if max heating time has passed.
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- **heatUp()** will be obsolete in the future.
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#### Async interface
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See async example for usage
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- **requestData()** requests a new measurement. Returns false if this fails.
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- **dataReady()** checks if enough time has passed to read the data. (15 millis)
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- **readData(bool fast = true)** fast skips CRC check. Returns false if reading fails or in case of a CRC fail.
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## Status fields
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| BIT | Description | values |
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|:----:|:----|:----|
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| 15 | Alert pending status | '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 | '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 | '0<> : no alert - default |
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| | | '1<> : alert |
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| 10 | Temperature tracking alert | '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 | '0': no reset since last <20>clear status register<65> 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 | '0': last cmd executed successfully |
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| | | '1': last cmd not processed. Invalid or failed checksum |
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| 0 | Write data checksum status | '0': checksum of last write correct |
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| | | '1': checksum of last write transfer failed |
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## Operation
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2020-11-27 05:33:55 -05:00
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See examples
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