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0.1.4 SHT85
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‎libraries/SHT85/README.md‎

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[![Arduino CI](https://github.com/robtillaart/SHT85/workflows/Arduino%20CI/badge.svg)](https://github.com/marketplace/actions/arduino_ci)
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[![GitHub release](https://img.shields.io/github/release/RobTillaart/SHT85.svg?maxAge=3600)](https://github.com/RobTillaart/SHT85/releases)
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[![JSON check](https://github.com/RobTillaart/SHT85/actions/workflows/jsoncheck.yml/badge.svg)](https://github.com/RobTillaart/SHT85/actions/workflows/jsoncheck.yml)
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[![Arduino-lint](https://github.com/RobTillaart/SHT85/actions/workflows/arduino-lint.yml/badge.svg)](https://github.com/RobTillaart/SHT85/actions/workflows/arduino-lint.yml)
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[![License: MIT](https://img.shields.io/badge/license-MIT-green.svg)](https://github.com/RobTillaart/SHT85/blob/master/LICENSE)
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[![GitHub release](https://img.shields.io/github/release/RobTillaart/SHT85.svg?maxAge=3600)](https://github.com/RobTillaart/SHT85/releases)
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# SHT85
@@ -60,25 +62,28 @@ this is not verified yet.
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Need to investigate if the interface is identical?
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If so the libraries might be merged.
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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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## Interface
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#### Base interface
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68-
- **SHT85()** constructor.
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- **SHT85()** constructor.
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- **begin(address, dataPin, clockPin)** begin function for ESP8266 & ESP32; **WARNING: not verified yet**
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returns false if device address is incorrect or device cannot be reset.
71-
- **begin(address, TwoWire \*wire = &Wire)** for platforms with multiple I2C busses.
72-
- **read(bool fast = true)** blocks 4 (fast) or 15 (slow) milliseconds + actual read + math.
76+
- **bool begin(address, TwoWire \*wire = &Wire)** for platforms with multiple I2C busses.
77+
- **bool read(bool fast = true)** blocks 4 (fast) or 15 (slow) milliseconds + actual read + math.
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Does read both the temperature and humidity.
74-
- **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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- **bool 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()** computes the relative humidity in % based off the latest raw reading, and returns it
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- **getTemperature()** computes the temperature in °C based off the latest raw reading, and returns it
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- **getRawHumidity()** returns the raw two-byte representation of humidity directly from the sensor
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- **getRawTemperature()** returns the raw two-byte representation of temperature directly from the sensor
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- **bool reset(bool hard = false)** resets the sensor, soft reset by default. Returns false if fails.
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- **float getHumidity()** computes the relative humidity in % based off the latest raw reading, and returns it.
84+
- **float getTemperature()** computes the temperature in °C based off the latest raw reading, and returns it.
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- **uint16_t getRawHumidity()** returns the raw two-byte representation of humidity directly from the sensor.
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- **uint16_t getRawTemperature()** returns the raw two-byte representation of temperature directly from the sensor.
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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.
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@@ -88,67 +93,77 @@ Note that the temperature and humidity values are recalculated on every call to
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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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91-
| Error | Symbolic | Description |
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|:----:|:----|:----|
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| 0x00 | SHT_OK | no error |
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| 0x81 | SHT_ERR_WRITECMD | I2C write failed |
95-
| 0x82 | SHT_ERR_READBYTES | I2C read failed |
96-
| 0x83 | SHT_ERR_HEATER_OFF | Could not switch off heater |
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| 0x84 | SHT_ERR_NOT_CONNECT | Could not connect |
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| 0x85 | SHT_ERR_CRC_TEMP | CRC error in temperature |
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| 0x86 | SHT_ERR_CRC_HUM | CRC error in humidity |
100-
| 0x87 | SHT_ERR_CRC_STATUS | CRC error in statusfield |
96+
| Error | Symbolic | Description
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|:-----:|:--------------------------|:----------------------------|
98+
| 0x00 | SHT_OK | no error |
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| 0x81 | SHT_ERR_WRITECMD | I2C write failed |
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| 0x82 | SHT_ERR_READBYTES | I2C read failed |
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| 0x83 | SHT_ERR_HEATER_OFF | Could not switch off heater |
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| 0x84 | SHT_ERR_NOT_CONNECT | Could not connect |
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| 0x85 | SHT_ERR_CRC_TEMP | CRC error in temperature |
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| 0x86 | SHT_ERR_CRC_HUM | CRC error in humidity |
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| 0x87 | SHT_ERR_CRC_STATUS | CRC error in statusfield |
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| 0x88 | SHT_ERR_HEATER_COOLDOWN | Heater need to cool down |
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| 0x88 | SHT_ERR_HEATER_ON | Could not switch on heater |
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#### Heater interface
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105-
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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Use the heater for max **180** seconds, and let it cool down **180** seconds = 3 minutes.
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Version 0.3.3 and up guards the cool down time by preventing switching the heater on
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within **180** seconds of the last switch off. Note: this guarding is not reboot persistent.
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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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**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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Switch off the heater by directly calling **heatOff()** or indirectly by calling **isHeaterOn()**.
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112-
- **setHeatTimeout(uint8_t seconds)** Set the time out of the heat cycle.
123+
- **void setHeatTimeout(uint8_t seconds)** Set the time out of the heat cycle.
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This value is truncated to max 180 seconds.
114-
- **heatOn()** switches heat cycle on. Returns false if fails.
115-
- **heatOff()** switches heat cycle off. Returns false if fails.
116-
- **isHeaterOn()** is the sensor still in heating cycle? replaces **heatUp()**.
117-
Will switch heat off if max heating time has passed.
118-
- **heatUp()** will be obsolete in the future.
125+
- **uint8_t getHeatTimeout
126+
- **bool heatOn()** switches heat cycle on if not already on.
127+
Returns false if fails, setting error to **SHT_ERR_HEATER_COOLDOWN**
128+
or to **SHT_ERR_HEATER_ON**.
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- **bool heatOff()** switches heat cycle off.
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Returns false if fails, setting error to **SHT_ERR_HEATER_OFF**.
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- **bool isHeaterOn()** is the sensor still in heating cycle? replaces **heatUp()**.
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Will switch the heater off if max heating time has passed.
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#### Async interface
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See async example for usage
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125-
- **requestData()** requests a new measurement. Returns false if this fails.
126-
- **dataReady()** checks if enough time has passed to read the data. (15 milliseconds)
127-
- **readData(bool fast = true)** fast skips CRC check. Returns false if reading fails or in case of a CRC fail.
139+
- **bool requestData()** requests a new measurement. Returns false if this fails.
140+
- **bool dataReady()** checks if enough time has passed to read the data. (15 milliseconds)
141+
- **bool readData(bool fast = true)** fast = true skips the CRC check.
142+
Returns false if reading fails or in case of a CRC failure.
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130145
## Status fields
131146

132-
| BIT | Description | values |
133-
|:----:|:----|:----|
134-
| 15 | Alert pending status | '0' : no pending alerts|
135-
| | | '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 |
138-
| | | '1’ : Heater ON |
139-
| 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 ‘clear status register’ command |
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| | | '1' : reset detected (hard or soft reset command or supply fail) - default |
147-
| 3-2 | Reserved | '00' |
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| 1 | Command status | '0' : last command executed successfully |
149-
| | | '1' : last command not processed. Invalid or failed checksum |
150-
| 0 | Write data checksum status | '0' : checksum of last write correct |
151-
| | | '1' : checksum of last write transfer failed |
147+
| BIT | Description | value | notes |
148+
|:-----|:---------------------------|:--------|:------|
149+
| 15 | Alert pending status | 0 | no pending alerts
150+
| | | 1 | at least one pending alert - default
151+
| 14 | Reserved | 0 |
152+
| 13 | Heater status | 0 | Heater OFF - default
153+
| | | 1 | Heater ON
154+
| 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 ‘clear status register’ command
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| | | 1 | reset detected (hard or soft reset command or supply fail) - default
162+
| 3-2 | Reserved | 00 |
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| 1 | Command status | 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 | 0 | checksum of last write correct
166+
| | | 1 | checksum of last write transfer failed
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## Future
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- SHT_BASE class ?
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- investigate command ART (auto sampling at 4 Hz)
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- investigate command BREAK (stop auto sampling)
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- direct Fahrenheit formula ?
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- improve error handling / status. (all code paths)
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## Operation

‎libraries/SHT85/SHT85.cpp‎

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//
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// FILE: SHT85.cpp
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// AUTHOR: Rob Tillaart
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// VERSION: 0.1.3
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// VERSION: 0.1.4
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// DATE: 2021-02-10
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// PURPOSE: Arduino library for the SHT85 temperature and humidity sensor
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// https://nl.rs-online.com/web/p/temperature-humidity-sensor-ics/1826530
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// 0.1.1 2021-03-13 initial release
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// 0.1.2 2021-05-27 fix Arduino-lint
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// 0.1.3 2021-08-06 expose raw data from sensor
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// 0.1.4 2021-08-24 prevent heater to switch on too fast.
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// update readme
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#include "SHT85.h"
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#define SHT_HEAT_ON 0x306D
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#define SHT_HEAT_OFF 0x3066
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35+
#define SHT_HEATER_TIMEOUT 180000UL // milliseconds
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SHT85::SHT85()
3638
{
37-
_addr = 0;
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_address = 0;
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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 = SHT_OK;
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}
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{
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return false;
5257
}
53-
_addr = address;
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_address = address;
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_wire = &Wire;
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if ((dataPin < 255) && (clockPin < 255))
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7075
{
7176
return false;
7277
}
73-
_addr = address;
74-
_wire = wire;
78+
_address = address;
79+
_wire = wire;
7580
_wire->begin();
7681
return reset();
7782
}
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bool SHT85::isConnected()
9297
{
93-
_wire->beginTransmission(_addr);
98+
_wire->beginTransmission(_address);
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int rv = _wire->endTransmission();
95100
if (rv != 0) _error = SHT_ERR_NOT_CONNECT;
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return (rv == 0);
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166171
void SHT85::setHeatTimeout(uint8_t seconds)
167172
{
168-
_heatTimeOut = seconds;
169-
if (_heatTimeOut > 180) _heatTimeOut = 180;
173+
_heatTimeout = seconds;
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if (_heatTimeout > 180) _heatTimeout = 180;
170175
}
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bool SHT85::heatOn()
174179
{
180+
if (isHeaterOn()) return true;
181+
if ((_heaterStop > 0) && (millis() - _heaterStop < SHT_HEATER_TIMEOUT))
182+
{
183+
_error = SHT_ERR_HEATER_COOLDOWN;
184+
return false;
185+
}
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if (writeCmd(SHT_HEAT_ON) == false)
176187
{
188+
_error = SHT_ERR_HEATER_ON;
177189
return false;
178190
}
179191
_heaterStart = millis();
192+
_heaterOn = true;
180193
return true;
181194
}
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184197
bool SHT85::heatOff()
185198
{
199+
// always switch off the heater - ignore _heaterOn flag.
186200
if (writeCmd(SHT_HEAT_OFF) == false)
187201
{
188202
_error = SHT_ERR_HEATER_OFF; // can be serious!
189203
return false;
190204
}
191-
_heaterStart = 0;
205+
_heaterStop = millis();
206+
_heaterOn = false;
192207
return true;
193208
}
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196211
bool SHT85::isHeaterOn()
197212
{
198-
if (_heaterStart == 0)
213+
if (_heaterOn == false)
199214
{
200215
return false;
201216
}
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// did not exceed time out
203-
if (millis() - _heaterStart < (_heatTimeOut * 1000UL))
218+
if (millis() - _heaterStart < (_heatTimeout * 1000UL))
204219
{
205220
return true;
206221
}
207-
heatOff(); // should this be done here?
222+
heatOff();
208223
return false;
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}
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289304
bool SHT85::writeCmd(uint16_t cmd)
290305
{
291-
_wire->beginTransmission(_addr);
306+
_wire->beginTransmission(_address);
292307
_wire->write(cmd >> 8 );
293308
_wire->write(cmd & 0xFF);
294309
if (_wire->endTransmission() != 0)
@@ -302,7 +317,7 @@ bool SHT85::writeCmd(uint16_t cmd)
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303318
bool SHT85::readBytes(uint8_t n, uint8_t *val)
304319
{
305-
int rv = _wire->requestFrom(_addr, (uint8_t) n);
320+
int rv = _wire->requestFrom(_address, (uint8_t) n);
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if (rv == n)
307322
{
308323
for (uint8_t i = 0; i < n; i++)

‎libraries/SHT85/SHT85.h‎

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//
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// FILE: SHT85.h
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// AUTHOR: Rob Tillaart
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// VERSION: 0.1.3
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// VERSION: 0.1.4
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// DATE: 2021-02-10
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// PURPOSE: Arduino library for the SHT85 temperature and humidity sensor
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// https://nl.rs-online.com/web/p/temperature-humidity-sensor-ics/1826530
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#include "Wire.h"
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#define SHT85_LIB_VERSION (F("0.1.3"))
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#define SHT85_LIB_VERSION (F("0.1.4"))
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// fields readStatus
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4646
#define SHT_ERR_CRC_TEMP 0x85
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#define SHT_ERR_CRC_HUM 0x86
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#define SHT_ERR_CRC_STATUS 0x87
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#define SHT_ERR_HEATER_COOLDOWN 0x88
50+
#define SHT_ERR_HEATER_ON 0x89
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class SHT85
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7577
// do not use heater for long periods,
7678
// use it for max 3 minutes to heat up
77-
// and let it cool down an equal period.
79+
// and let it cool down at least 3 minutes.
7880
void setHeatTimeout(uint8_t seconds);
81+
uint8_t getHeatTimeout() { return _heatTimeout; };
82+
;
7983
bool heatOn();
8084
bool heatOff();
8185
bool isHeaterOn(); // is the sensor still heating up?
@@ -100,11 +104,13 @@ class SHT85
100104
bool readBytes(uint8_t n, uint8_t *val);
101105
TwoWire* _wire;
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103-
uint8_t _addr;
104-
uint8_t _heatTimeOut; // seconds
107+
uint8_t _address;
108+
uint8_t _heatTimeout; // seconds
105109
uint32_t _lastRead;
106110
uint32_t _lastRequest; // for async interface
107111
uint32_t _heaterStart;
112+
uint32_t _heaterStop;
113+
bool _heaterOn;
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109115
uint16_t _rawHumidity;
110116
uint16_t _rawTemperature;

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