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add getSerialNumber() for SHT85 (#18)
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- add **uint32_t getSerialNumber()** for SHT85 (no CRC check).
- improve error handling.
- update readme.md
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@RobTillaart
RobTillaart authored May 9, 2023
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14 changes: 10 additions & 4 deletions CHANGELOG.md
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Expand Up @@ -6,6 +6,12 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/)
and this project adheres to [Semantic Versioning](http://semver.org/).


## [0.4.1] - 2022-05-09
- add **uint32_t getSerialNumber()** for SHT85 (no CRC check).
- improve error handling.
- update readme.md


## [0.4.0] - 2022-12-14
- redo asynchronous interface
- add **uint32_t getLastRequest()** timestamp.
Expand All @@ -28,14 +34,14 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
## [0.3.2] - 2022-01-17
- fix #8 add SHT_DEFAULT_ADDRESS + 2x begin()

## [0.3.1] - 2021-12-28
## [0.3.1] - 2021-12-28
- update library.json
- update readme.md
- update license
- minor edits

## [0.3.0] - 2021-10-20
- Fix #6 image in documentation,
## [0.3.0] - 2021-10-20
- Fix #6 image in documentation,
- pdate build-CI

----
Expand All @@ -46,7 +52,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).

----

## [0.1.4] - 2021-08-24
## [0.1.4] - 2021-08-24
- prevent heater to switch on too fast.
- update readme

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89 changes: 51 additions & 38 deletions README.md
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Expand Up @@ -12,7 +12,7 @@ Arduino library for the SHT85 temperature and humidity sensor.

Based upon the SHT31 library - https://github.com/RobTillaart/SHT31
however this library will be leading in the future as it implements derived classes
for the following sensors: **SHT30, SHT31, SHT35 and SHT85.**.
for the following sensors: **SHT30, SHT31, SHT35 and SHT85**.


**WARNING** to keep self-heating below 0.1°C, the SHT85 sensor should
Expand Down Expand Up @@ -63,9 +63,9 @@ At 10% load the SHT85 can be used to make about 10-15 SPS.

#### Compatibility

The SHT85 is protocom compatible with the SHT3x series.
The SHT85 is protocol compatible with the SHT3x series.
Main difference is the accuracy.
Compare the datasheets to see all differences.
Compare the data sheets to see all differences.

Accuracy table:

Expand All @@ -91,7 +91,7 @@ The SHT4x series is slightly faster than the SHT3x series.
An elaborated library for the SHT31 sensor can be found here
- https://github.com/hawesg/SHT31D_Particle_Photon_ClosedCube

Dewpoint, heatindex and related functions
Dewpoint, heatindex, related functions and conversions.
- https://github.com/RobTillaart/Temperature


Expand All @@ -111,18 +111,19 @@ Dewpoint, heatindex and related functions
- **SHT85()** constructor.
- **uint8_t getType()** returns numeric part of sensor type.
Returns 0 for the base class.
- **bool begin(uint8_t address, uint8_t dataPin, uint8_t clockPin)** begin function for ESP8266 & ESP32; **WARNING: not verified yet**
returns false if device address is incorrect or device cannot be reset.
- **bool begin(uint8_t address, uint8_t dataPin, uint8_t clockPin)** begin function for ESP8266, ESP32 and similar. **WARNING: not verified yet**.
Returns false if device address is incorrect or device cannot be reset.
- **bool begin(uint8_t dataPin, uint8_t clockPin)** same as above.
Uses SHT_DEFAULT_ADDRESS (0x44) as address.
- **bool begin(uint8_t address, TwoWire \*wire = &Wire)** for platforms with multiple I2C buses. Default Wire as I2C bus.
- **bool begin(uint8_t address, TwoWire \*wire = &Wire)** for platforms with multiple I2C buses. The default I2C bus is Wire.
Returns false if device address is incorrect or device cannot be reset.
- **bool begin(TwoWire \*wire = &Wire)** same as above.
Uses SHT_DEFAULT_ADDRESS (0x44) as address.


#### Status

- **bool isConnected()** check sensor is reachable over I2C. Returns false if not connected.
- **bool isConnected()** checks if address of the 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 fails.
Expand All @@ -131,7 +132,7 @@ Uses SHT_DEFAULT_ADDRESS (0x44) as address.
#### Synchronous read

- **bool read(bool fast = true)** blocks 4 (fast) or 15 (slow) milliseconds + actual read + math.
Does read both the temperature and humidity.
Reads both the temperature and humidity from the device.

Note: the medium level is not supported (yet).

Expand All @@ -142,34 +143,38 @@ See async example for usage.

- **bool requestData(bool fast = true)** requests a new measurement.
Returns false if the request fails.
Set a timestamp.
Records the timestamp of the request if successful.
- **bool dataReady(bool fast = true)** Checks if appropriate time (4 / 15 ms)
has past since request to read the data.
The parameter **fast** should be the same as in requestData().
- **bool readData(bool fast = true)** fast = true skips the CRC check.
Returns false if reading the data fails or if CRC check failed.
- **uint32_t getLastRequest()** returns timestamp of last requestData.
- **uint32_t getLastRequest()** returns timestamp of last successful call to requestData.
This function is used to check if the request is too long ago.


#### Temperature and humidity

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.
you've performed a new **read()**.

- **float getHumidity()** computes the relative humidity in % based on the latest raw reading, and returns it.
- **float getTemperature()** computes the temperature in °C based on the latest raw reading, and returns it.
- **float getHumidity()** computes the relative humidity in % based on the latest raw reading. This includes the optional offset.
- **float getTemperature()** computes the temperature in °C based on the latest raw reading. This includes the optional offset.
- **float getFahrenheit()** computes the temperature in °F based on the latest raw reading, and returns it.
Note that the optional offset is set in °Celsius.


The **getRawHumidity()** and **getRawTemperature()** can be used to minimize storage or communication.
The **getRawHumidity()** and **getRawTemperature()** can be used to minimize storage or communication as the data type is 50% smaller.
Another application is faster comparison with a previous value or threshold.
However comparisons are quite fast.

- **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.

The library has no **CelsiusToRaw()** function although this is relative easy.
```

```cpp
rawTemperatureC = (tempC + 45) * (65535 / 175.0);
rawTemperatureF = (tempF + 49) * (65535 / 315.0);
rawHumidity = humidity * 655.35;
Expand All @@ -179,15 +184,15 @@ rawHumidity = humidity * 655.35;
#### Temperature and humidity offset

Default the offset is zero for both temperature and humidity.
These functions allows one to adjust them a little.
These functions allows one to adjust them a little. Note there is no limit to the offset so one can use huge values. This allows to use an offset of 273.15 effectively creating **°Kelvin** instead of Celsius.

Note: the offset is in degrees Celsius.
To set an offset in degrees Fahrenheit, multiply the Fahrenheit offset with 0.55555556 to get Celsius steps.
So 4°F becomes 2.2222°C.
Note: the offset is defined in degrees Celsius.
To set an offset in degrees Fahrenheit, multiply the Fahrenheit offset with 0.55555556 to get Celsius steps (divide by 1.8 is slower).
So an offset of 4 °F becomes 2.2222 °C.


- **void setTemperatureOffset(float offset = 0)** set the offset, default is zero removing the offset.
- **float getTemperatureOffset()** returns the set offset.
- **void setTemperatureOffset(float offset = 0)** set the offset in °C, default is zero removing the offset. The library converts this internally
- **float getTemperatureOffset()** returns the set offset in °C.
- **void setHumidityOffset(float offset = 0)** set the offset, default is zero removing the offset.
- **float getHumidityOffset()** returns the set offset.

Expand All @@ -198,18 +203,19 @@ So 4
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 | SHT_OK | no error |
| 0x81 | SHT_ERR_WRITECMD | I2C write failed |
| 0x82 | SHT_ERR_READBYTES | I2C read failed |
| 0x83 | SHT_ERR_HEATER_OFF | Could not switch off heater |
| 0x84 | SHT_ERR_NOT_CONNECT | Could not connect |
| 0x85 | SHT_ERR_CRC_TEMP | CRC error in temperature |
| 0x86 | SHT_ERR_CRC_HUM | CRC error in humidity |
| 0x87 | SHT_ERR_CRC_STATUS | CRC error in status field |
| 0x88 | SHT_ERR_HEATER_COOLDOWN | Heater need to cool down |
| 0x89 | SHT_ERR_HEATER_ON | Could not switch on heater |
| Error | Symbolic | Description |
|:-------:|:--------------------------|:-------------------------------|
| 0x00 | SHT_OK | no error |
| 0x81 | SHT_ERR_WRITECMD | I2C write failed |
| 0x82 | SHT_ERR_READBYTES | I2C read failed |
| 0x83 | SHT_ERR_HEATER_OFF | Could not switch off heater |
| 0x84 | SHT_ERR_NOT_CONNECT | Could not connect |
| 0x85 | SHT_ERR_CRC_TEMP | CRC error in temperature |
| 0x86 | SHT_ERR_CRC_HUM | CRC error in humidity |
| 0x87 | SHT_ERR_CRC_STATUS | CRC error in status field |
| 0x88 | SHT_ERR_HEATER_COOLDOWN | Heater need to cool down |
| 0x89 | SHT_ERR_HEATER_ON | Could not switch on heater |
| 0x8A | SHT_ERR_SERIAL | Could not read serial number |


#### Heater interface
Expand Down Expand Up @@ -261,6 +267,13 @@ Will switch the heater off if maximum heating time has passed.
| | | 1 | checksum of last write transfer failed


#### SHT85 specific

- **uint32_t GetSerialNumber()** Returns a 32 bit unique serial number.
This command seems to be timing sensitive, it uses a delay of 500us
which may need "tuning". So function is bit experimental.


## Future


Expand All @@ -273,21 +286,20 @@ Will switch the heater off if maximum heating time has passed.

- more testing (including heater)
- verify working with ESP32
- improve error handling / status.
- all code paths
- reset to OK
- support for medium level read.
- 3 levels iso 2.


#### Could

- remember the fast parameter of **requestData()** so it
can become obsolete for **radaReady()**.
- investigate command ART (auto sampling at 4 Hz)
- investigate command BREAK (stop auto sampling)
- test SHT30/35


#### won't
#### Won't

- rename the library? to SHT ? or sensirion.h ?
- not on short term
Expand All @@ -299,4 +311,5 @@ Will switch the heater off if maximum heating time has passed.
- merge with other SHT sensors if possible?
- derived classes fixes this enough.
- **getKelvin()** wrapper? (no => check temperature class)
==> set Offset to 273.15 !

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