mirror of
https://github.com/RobTillaart/Arduino.git
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118 lines
4.0 KiB
Markdown
118 lines
4.0 KiB
Markdown
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[](https://github.com/marketplace/actions/arduino_ci)
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[](https://github.com/RobTillaart/DHT20/actions/workflows/arduino-lint.yml)
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[](https://github.com/RobTillaart/DHT20/actions/workflows/jsoncheck.yml)
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[](https://github.com/RobTillaart/DHT20/blob/master/LICENSE)
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[](https://github.com/RobTillaart/DHT20/releases)
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# DHT20
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Arduino library for I2C DHT20 temperature and humidity sensor.
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## Description
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The library must be initiated by calling the **begin()** function,
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or **begin(dataPin, clockPin)** for **ESP32** and similar platforms.
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Thereafter one has to call the **read()** function to do the actual reading,
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and with **getTemperature()** and **getHumidity()** to get the measured values.
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Calling these latter again will return the same values until a new **read()** is called.
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The **read()** call of this sensor is blocking for 80+ milliseconds (datasheet 7.4)
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so the library also has a asynchronous interface. See below.
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## Interface
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### Constructor
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- **DHT20(TwoWire \*wire = &Wire)** constructor, using a specific Wire (I2C bus).
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- **bool begin(uint8_t dataPin, uint8_t clockPin)** begin for ESP32 et al, to set I2C bus pins.
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- **bool begin()** initializer for non ESP32. Returns true if connected.
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- **bool isConnected()** returns true if the address of the DHT20 can be seen on the I2C bus.
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### Core
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- **int8_t read()** read the sensor and store the values internally.
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It returns the status of the read which should be 0.
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- **float getHumidity()** returns last Humidity read.
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- **float getTemperature()** returns last Temperature read.
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### Offset
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- **void setHumOffset(float offset)** set an offset to calibrate (1st order) the sensor.
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- **float getHumOffset()** return current offset, default 0.
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- **void setTempOffset(float offset)** set an offset to calibrate (1st order) the sensor.
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- **float getTempOffset()** return current offset, default 0.
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### Asynchronous interface
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The async interface allows one to continue processing after a **requestData()** has been made.
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One can check **readyData()** and if it returns true, enough time has
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passed to make the measurement and the sensor can be read with **readData()**.
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- **int requestData()** signals the sensor to make a new measurement.
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- **bool readyData()** returns true if 85 milliseconds have passed since the last **requestData()** call.
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The time of 85 ms is hard coded.
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- **int readData()** does the actual reading of the data.
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### Miscellaneous
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- **uint32_t lastRead()** last time the sensor is read in milliseconds since start.
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- **uint32_t lastRequest()** last time a request is made to make a measurement.
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- **int internalStatus()** returns the internal status of the sensor. (debug ?).
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### Return codes
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TODO: fix incomplete list
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| name | value |
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|:----------------------|:-------:|
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| DHT20_OK | 00 |
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| DHT20_ERROR_CHECKSUM | -10 |
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| DHT20_ERROR_CONNECT | -11 |
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| DHT20_MISSING_BYTES | -12 |
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## Operation
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See examples
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## Future
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- update documentation
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- add missing error codes
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- describe async interface
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- test more in detail
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- test on ESP32
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- improve unit tests.
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- improve the code (check return codes etc.)
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- investigate
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- status register bits
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- sensor calibration (website aosong?)
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- check for optimizations.
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- mainly for asynchronous
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- test at different I2C speeds 400 KHz should be possible.
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- 85 ms wait time?
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- add examples
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- asynchronous
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-
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#### won't
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- **void setIgnoreChecksum(bool = false)** ignore checksum flag speeds up communication a bit
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- **bool getIgnoreChecksum()** get status. for completeness.
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-
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