GY-63_MS5611/libraries/DHT20

DHT20

Arduino library for I2C DHT20 temperature and humidity sensor.

Description

The library must be initiated by calling the begin() function, or begin(dataPin, clockPin) for ESP32 and similar platforms.

Thereafter one has to call the read() function to do the actual reading, and with getTemperature() and getHumidity() to get the measured values. Calling these latter again will return the same values until a new read() is called.

The read() call of this sensor is blocking for 80+ milliseconds (datasheet 7.4) so the library also has a asynchronous interface. See below.

Interface

Constructor

• DHT20(TwoWire *wire = &Wire) constructor, using a specific Wire (I2C bus).
• bool begin(uint8_t dataPin, uint8_t clockPin) begin for ESP32 et al, to set I2C bus pins.
• bool begin() initializer for non ESP32. Returns true if connected.
• bool isConnected() returns true if the address of the DHT20 can be seen on the I2C bus.

Core

• int8_t read() read the sensor and store the values internally. It returns the status of the read which should be 0.
• float getHumidity() returns last Humidity read.
• float getTemperature() returns last Temperature read.

Offset

• void setHumOffset(float offset) set an offset to calibrate (1st order) the sensor.
• float getHumOffset() return current offset, default 0.
• void setTempOffset(float offset) set an offset to calibrate (1st order) the sensor.
• float getTempOffset() return current offset, default 0.

Asynchronous interface

The async interface allows one to continue processing after a requestData() has been made. One can check readyData() and if it returns true, enough time has passed to make the measurement and the sensor can be read with readData().

• int requestData() signals the sensor to make a new measurement.
• bool readyData() returns true if 85 milliseconds have passed since the last requestData() call. The time of 85 ms is hard coded.
• int readData() does the actual reading of the data.

Miscellaneous

• uint32_t lastRead() last time the sensor is read in milliseconds since start.
• uint32_t lastRequest() last time a request is made to make a measurement.
• int internalStatus() returns the internal status of the sensor. (debug ?).

Return codes

TODO: fix incomplete list

name	value
DHT20_OK	00
DHT20_ERROR_CHECKSUM	-10
DHT20_ERROR_CONNECT	-11
DHT20_MISSING_BYTES	-12

Operation

See examples

Future

• update documentation
  • add missing error codes
  • describe async interface
• test more in detail
  • test on ESP32
• improve unit tests.
• improve the code (check return codes etc.)
• investigate
  • status register bits
  • sensor calibration (website aosong?)
• check for optimizations.
  • mainly for asynchronous
  • test at different I2C speeds 400 KHz should be possible.
  • 85 ms wait time?
• add examples
  • asynchronous

won't

• void setIgnoreChecksum(bool = false) ignore checksum flag speeds up communication a bit
• bool getIgnoreChecksum() get status. for completeness.