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0.2.0 DHT20
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rob tillaart
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commit
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@ -1,3 +1,18 @@
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platforms:
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rpipico:
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board: rp2040:rp2040:rpipico
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package: rp2040:rp2040
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gcc:
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features:
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defines:
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- ARDUINO_ARCH_RP2040
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warnings:
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flags:
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packages:
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rp2040:rp2040:
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url: https://github.com/earlephilhower/arduino-pico/releases/download/global/package_rp2040_index.json
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compile:
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# Choosing to run compilation tests on 2 different Arduino platforms
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platforms:
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@ -8,4 +23,6 @@ compile:
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- m4
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- esp32
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# - esp8266
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# - mega2560
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# - mega2560
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- rpipico
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44
libraries/DHT20/CHANGELOG.md
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44
libraries/DHT20/CHANGELOG.md
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# Change Log DHT20
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All notable changes to this project will be documented in this file.
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The format is based on [Keep a Changelog](http://keepachangelog.com/)
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and this project adheres to [Semantic Versioning](http://semver.org/).
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## [0.2.0] - 2022-10-30
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- add changelog.md
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- add rp2040 to build-CI
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- add workaround for #8 to readme.md
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- fix requestFrom() ambiguity
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- fix #8 - embed **resetSensor()** into **read()**.
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This makes reads slightly slower.
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- update readme.md
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----
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## [0.1.4] - 2022-09-18
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- add resetSensor() code.
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- add comments in .h file
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- add examples
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- stabilize readStatus()
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- update readme.md
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## [0.1.3] - 2022-09-17
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- add wrapper status functions
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- improve performance read()
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- refactor, update readme.md
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## [0.1.2] - 2022-09-16
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- fix #4 DHT20_ERROR_BYTES_ALL_ZERO error condition.
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- fix keywords
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- add readStatus() fix _readStatus()
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- add setWireTimeout(250000, true); // in comments
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## [0.1.1] - 2022-09-10
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- add hardware schema to readme.md.
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- fix async interface (first version)
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## [0.1.0] - 2022-01-11
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- initial version (based upon DHT20 datasheet)
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@ -1,25 +1,10 @@
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//
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// FILE: DHT20.cpp
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// AUTHOR: Rob Tillaart
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// VERSION: 0.1.4
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// VERSION: 0.2.0
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// PURPOSE: Arduino library for DHT20 I2C temperature and humidity sensor.
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//
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// HISTORY:
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// 0.1.0 2022-01-11 initial version (based upon DHT20 datasheet)
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// 0.1.1 2022-09-10 add hardware schema to readme.md.
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// fix async interface (first version)
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// 0.1.2 2022-09-16 fix #4 DHT20_ERROR_BYTES_ALL_ZERO error condition.
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// fix keywords
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// add readStatus() fix _readStatus()
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// add setWireTimeout(250000, true); // in comments
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// 0.1.3 2022-09-17 add wrapper status functions
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// improve performance read()
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// refactor, update readme.md
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// 0.1.4 2022-09-18 add resetSensor() code.
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// add comments in .h file
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// add examples
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// stabilize readStatus()
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// update readme.md
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// HISTORY: see changelog.md
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#include "DHT20.h"
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@ -117,13 +102,16 @@ int DHT20::read()
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status = readData();
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if (status < 0) return status;
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// convert it to meaningfull data
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// convert it to meaningful data
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return convert();
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}
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int DHT20::requestData()
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{
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// reset sensor if needed.
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resetSensor();
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// GET CONNECTION
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_wire->beginTransmission(DHT20_ADDRESS);
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_wire->write(0xAC);
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@ -331,7 +319,7 @@ bool DHT20::_resetRegister(uint8_t reg)
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if (_wire->endTransmission() != 0) return false;
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delay(5);
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int bytes = _wire->requestFrom(DHT20_ADDRESS, 3);
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int bytes = _wire->requestFrom(DHT20_ADDRESS, (uint8_t)3);
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for (int i = 0; i < bytes; i++)
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{
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value[i] = _wire->read();
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@ -3,7 +3,7 @@
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// FILE: DHT20.h
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// AUTHOR: Rob Tillaart
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// PURPOSE: Arduino library for DHT20 I2C temperature and humidity sensor.
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// VERSION: 0.1.4
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// VERSION: 0.2.0
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// HISTORY: See DHT20.cpp
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// URL: https://github.com/RobTillaart/DHT20
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//
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@ -21,7 +21,7 @@
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#include "Arduino.h"
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#include "Wire.h"
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#define DHT20_LIB_VERSION (F("0.1.4"))
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#define DHT20_LIB_VERSION (F("0.2.0"))
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#define DHT20_OK 0
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#define DHT20_ERROR_CHECKSUM -10
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@ -13,12 +13,17 @@ Arduino library for I2C DHT20 temperature and humidity sensor.
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## Description
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The DHT20 is a humidity an temperature sensor.
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The sensor has a fixed address of **0x38**.
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It is not known if the address can be changed.
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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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and call **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 done.
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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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@ -27,9 +32,30 @@ Since 0.1.3 and 0.1.4 the performance of **read()** has been optimized,
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still blocking but less long for about 45 milliseconds.
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### 0.2.0
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In #8 a bug is described that the sensor "freezes".
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Cause is not well understood.
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Two solutions / workarounds are found:
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- call **resetSensor()** before EVERY **read()**.
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This is the preferred solution.
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- use **Wire.setClock(200000)** 100 K and lower speeds freezes the sensor.
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With clock set to 200 K and above the sensor seems to work for longer periods.
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Tested several speeds on UNO, no pull ups, < 10 cm wire.
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Note: setting the I2C clock possibly interferes with other devices on the I2C bus,
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so it is not a solution in the end.
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The 0.2.0 version embeds the **resetSensor()** into **requestData()** to
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reset the sensor if needed in both synchronous and asynchronous calls.
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This keeps the API simple. The reads are 1-2 ms slower than 0.1.4. (< 50 ms).
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Still far below the 80 ms mentioned in the datasheet.
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### Connection
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Always check datasheet
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Always check datasheet!
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Front view
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```
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@ -43,7 +69,7 @@ Front view
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### Tested
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Verified to work with Arduino UNO and ESP32.
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Verified to work with Arduino UNO and ESP32 and ESP8266 (see #8)
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Please let me know if other platforms work (or not).
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@ -61,29 +87,32 @@ Please let me know if other platforms work (or not).
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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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Returns the status of the read which should be 0 == **DHT20_OK**.
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- **float getHumidity()** returns last Humidity read.
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Multiple calls will return same value until a new **read()** is made.
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- **float getTemperature()** returns last Temperature read.
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Multiple calls will return same value until a new **read()** is made.
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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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- **void setHumOffset(float offset)** set an offset to calibrate the sensor (1st order).
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- **float getHumOffset()** return current humidity offset, default 0.
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- **void setTempOffset(float offset)** set an offset to calibrate the sensor (1st order).
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- **float getTempOffset()** return current temperature offset, default 0.
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### Asynchronous interface
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There are two timings that need to be considdered,
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- time between requests = 1000 ms
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- time between request and data ready = 80 ms
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There are two timings that need to be considered (from datasheet):
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- time between requests = 1000 ms.
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- time between request and data ready = 80 ms.
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The async interface allows one to continue processing after a **requestData()** has been made.
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Note that there should be at least **1000 milliseconds** between subsequent requests.
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Note there should be at least **1000 milliseconds** between subsequent requests.
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With **bool isMeasuring()** one can check if a new measurement is ready.
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Alternative is to delay for up to 80 ms.
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If so the sensor can be read with **readData()**.
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To interpret the read bits to temperature, humidity and status one needs to call **convert()** as last step.
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@ -116,7 +145,7 @@ This function blocks a few milliseconds to optimize communication.
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#### Experimental 0.1.4 resetSensor
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Use with care, as this is not tested.
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Use with care!
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- **uint8_t resetSensor()** if at startup the sensor does not return a status of 0x18,
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three registers 0x1B, 0x1C and 0x1E need to be reset.
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@ -124,6 +153,9 @@ See datasheet 7.4 Sensor Reading Process, point 1.
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There is no documentation about the meaning of these registers.
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The code is based upon example code for the AHT20 (from manufacturer).
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The call is needed to get the **read()** working well so it has been embedded into
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the read calls. (0.2.0)
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### Timing
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@ -152,20 +184,20 @@ See examples
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## Future
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#### must
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- improve documentation.
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- investigate the bug from #8 further
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#### should
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#### could
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- improve unit tests.
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- investigate
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- sensor calibration (website aosong?)
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- investigate optimizing timing in readStatus()
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- delay(1) ==> microSeconds(???).
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- separate changelog.md
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- connected flag?
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- add **uint8_t getAddress()** to return the address (convenience).
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#### won't
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@ -24,8 +24,6 @@ void setup()
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{
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DHT.begin(); // ESP32 default pins 21 22
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Wire.setClock(400000);
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Serial.begin(115200);
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Serial.println(__FILE__);
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Serial.print("DHT20 LIBRARY VERSION: ");
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18
libraries/DHT20/examples/DHT20/performance_0.2.0.txt
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18
libraries/DHT20/examples/DHT20/performance_0.2.0.txt
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...Arduino\libraries\DHT20\examples\DHT20\DHT20.ino
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DHT20 LIBRARY VERSION: 0.2.0
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IDE 1.8.19
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Arduino UNO
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Type Humidity (%) Temp (°C) Time (µs) Status
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DHT20 76.2 19.2 45964 OK
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DHT20 76.1 19.2 45960 OK
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DHT20 75.8 19.2 45956 OK
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DHT20 75.6 19.2 45952 OK
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DHT20 75.4 19.2 45972 OK
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DHT20 75.2 19.2 45976 OK
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DHT20 75.1 19.2 45964 OK
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DHT20 74.9 19.2 45960 OK
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DHT20 74.8 19.2 45956 OK
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DHT20 74.6 19.2 45960 OK
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@ -15,7 +15,7 @@
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"type": "git",
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"url": "https://github.com/RobTillaart/DHT20.git"
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},
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"version": "0.1.4",
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"version": "0.2.0",
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"license": "MIT",
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"frameworks": "arduino",
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"platforms": "*",
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@ -1,5 +1,5 @@
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name=DHT20
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version=0.1.4
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version=0.2.0
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author=Rob Tillaart <rob.tillaart@gmail.com>
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maintainer=Rob Tillaart <rob.tillaart@gmail.com>
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sentence=Arduino library for I2C DHT20 temperature and humidity sensor.
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