GY-63_MS5611/libraries/SHT31/README.md
2022-11-24 14:10:52 +01:00

7.4 KiB
Raw Blame History

Arduino CI JSON check Arduino-lint License: MIT GitHub release

SHT31

Arduino library for the SHT31 temperature and humidity sensor.

Relates to the SHT85 library - https://github.com/RobTillaart/SHT85

Description

The SHT3x family of sensors should work up to 1 MHz I2C

This library should also work for SHT30 and SHT35 but these are not tested yet.

Accuracy table

SENSOR Temperature Humidity
SHT30 ~0.3 2.0
SHT31 ~0.3 1.5
SHT35 ~0.2 1.5
SHT85 ~0.2 1.5

An elaborated library for the SHT31 sensor can be found here https://github.com/hawesg/SHT31D_Particle_Photon_ClosedCube

Interface

Base interface

  • SHT31() constructor.
  • bool begin(uint8_t address, uint8_t dataPin, uint8_t clockPin) begin function for ESP8266 & ESP32; returns false if device address is incorrect or device cannot be reset.
  • bool begin(uint8_t dataPin, uint8_t clockPin) same as above. With default SHT_DEFAULT_ADDRESS.
  • bool begin(uint8_t address, TwoWire *wire = &Wire) for platforms with multiple I2C buses.
  • bool begin(TwoWire *wire = &Wire) same as above. With default SHT_DEFAULT_ADDRESS.
  • bool read(bool fast = true) blocks 4 (fast) or 15 (slow) milliseconds + actual read + math. Does read both the temperature and humidity.
  • bool isConnected() check sensor is reachable over I2C. Returns false if not connected.
  • uint16_t readStatus() details see datasheet and Status fields below.
  • uint32_t lastRead() in milliSeconds since start of program.
  • bool reset(bool hard = false) resets the sensor, soft reset by default. Returns false if it fails.
  • float getHumidity() computes the relative humidity in % based on the latest raw reading, and returns it.
  • float getTemperature() computes the temperature in <20>C based on the latest raw reading, and returns it.
  • float getFahrenheit() computes the temperature in <20>F based on the latest raw reading, and returns it..
  • uint16_t getRawHumidity() returns the raw two-byte representation of humidity directly from the sensor.
  • uint16_t getRawTemperature() returns the raw two-byte representation of temperature directly from the sensor.

Note that the temperature and humidity values are recalculated on every call to getHumidity() and getTemperature(). If you're worried about the extra cycles, you should make sure to cache these values or only request them after you've performed a new reading.

Error interface

  • int getError() returns last set error flag and clear it. Be sure to clear the error flag by calling getError() before calling any command as the error flag could be from a previous command.
Error Symbolic Description
0x00 SHT31_OK no error
0x81 SHT31_ERR_WRITECMD I2C write failed
0x82 SHT31_ERR_READBYTES I2C read failed
0x83 SHT31_ERR_HEATER_OFF Could not switch off heater
0x84 SHT31_ERR_NOT_CONNECT Could not connect
0x85 SHT31_ERR_CRC_TEMP CRC error in temperature
0x86 SHT31_ERR_CRC_HUM CRC error in humidity
0x87 SHT31_ERR_CRC_STATUS CRC error in status field
0x88 SHT31_ERR_HEATER_COOLDOWN Heater need to cool down
0x88 SHT31_ERR_HEATER_ON Could not switch on heater

Heater interface

WARNING: Do not use heater for long periods.

Use the heater for max 180 seconds, and let it cool down 180 seconds = 3 minutes. Version 0.3.3 and up guards the cool down time by preventing switching the heater on within 180 seconds of the last switch off. Note: this guarding is not reboot persistent.

WARNING: The user is responsible to switch the heater off manually!

The class does NOT do this automatically. Switch off the heater by directly calling heatOff() or indirectly by calling isHeaterOn().

  • void setHeatTimeout(uint8_t seconds) Set the time out of the heat cycle. This value is truncated to max 180 seconds.
  • **uint8_t getHeatTimeout
  • bool heatOn() switches heat cycle on if not already on. Returns false if fails, setting error to SHT31_ERR_HEATER_COOLDOWN or to SHT31_ERR_HEATER_ON.
  • bool heatOff() switches heat cycle off. Returns false if fails, setting error to SHT31_ERR_HEATER_OFF.
  • bool isHeaterOn() is the sensor still in heating cycle? replaces heatUp(). Will switch the heater off if max heating time has passed.
  • bool heatUp() will be obsolete in the future. replaced by isHeaterOn()

Async interface

See async example for usage

  • bool requestData() requests a new measurement. Returns false if this fails.
  • bool dataReady() checks if enough time has passed to read the data. (15 milliseconds)
  • bool readData(bool fast = true) fast = true skips the CRC check. Returns false if reading fails or in case of a CRC failure.

Status fields

BIT Description value notes
15 Alert pending status 0 no pending alerts
1 at least one pending alert - default
14 Reserved 0
13 Heater status 0 Heater OFF - default
1 Heater ON
12 Reserved 0
11 Humidity tracking alert 0 no alert - default
1 alert
10 Temperature tracking alert 0 no alert - default
1 alert
9-5 Reserved 00000
4 System reset detected 0 no reset since last <20>clear status register<65> command
1 reset detected (hard or soft reset command or supply fail) - default
3-2 Reserved 00
1 Command status 0 last command executed successfully
1 last command not processed. Invalid or failed checksum
0 Write data checksum status 0 checksum of last write correct
1 checksum of last write transfer failed

Operation

See examples.

Future

  • keep in sync with SHT85 library
  • check TODO in code