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220 lines
7.8 KiB
Markdown
220 lines
7.8 KiB
Markdown
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[](https://github.com/marketplace/actions/arduino_ci)
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[](https://github.com/RobTillaart/AM2315C/actions/workflows/arduino-lint.yml)
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[](https://github.com/RobTillaart/AM2315C/actions/workflows/jsoncheck.yml)
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[](https://github.com/RobTillaart/AM2315C/issues)
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[](https://github.com/RobTillaart/AM2315C/blob/master/LICENSE)
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[](https://github.com/RobTillaart/AM2315C/releases)
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[](https://registry.platformio.org/libraries/robtillaart/AM2315C)
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# AM2315C
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Arduino library for I2C AM2315C temperature and humidity sensor.
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## Description
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The AM2315C is a humidity and temperature sensor.
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Warning: this sensor is not compatible with the AM2315.
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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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Thereafter one has to call the **read()** function to do the actual reading,
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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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This library is based upon the DHT20 library which is leading in development.
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The DHT20 also provides a bit more documentation and issues from the past.
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- https://github.com/RobTillaart/DHT20
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#### 0.2.0 Breaking change
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Version 0.2.0 introduced a breaking change.
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You cannot set the pins in **begin()** any more.
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This reduces the dependency of processor dependent Wire implementations.
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The user has to call **Wire.begin()** and can optionally set the Wire pins
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before calling **begin()**.
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## I2C
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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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#### I2C multiplexing
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Sometimes you need to control more devices than possible with the default
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address range the device provides.
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This is possible with an I2C multiplexer e.g. TCA9548 which creates up
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to eight channels (think of it as I2C subnets) which can use the complete
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address range of the device.
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Drawback of using a multiplexer is that it takes more administration in
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your code e.g. which device is on which channel.
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This will slow down the access, which must be taken into account when
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deciding which devices are on which channel.
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Also note that switching between channels will slow down other devices
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too if they are behind the multiplexer.
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- https://github.com/RobTillaart/TCA9548
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#### Connection
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Always check datasheet!
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Front view
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```
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+-----------------+
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RED -------- | VDD |
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YELLOW -------- | SDA AM2315C |
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BLACK -------- | GND |
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WHITE -------- | SCL |
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+-----------------+
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```
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## Interface
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```cpp
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#include "AM2315C.h"
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```
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#### Constructor
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- **AM2315C(TwoWire \*wire = &Wire)** constructor, using a specific Wire (I2C bus).
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- **bool begin()** initializer. Returns true if connected.
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The user must call **Wire.begin()** before calling this function.
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- **bool isConnected()** returns true if the address of the AM2315C can be seen on the I2C bus.
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- **uint8_t getAddress()** returns the (fixed) address - convenience.
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#### Core
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- **int8_t read()** read the sensor and store the values internally.
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Returns the status of the read which should be 0 == **AM2315C_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 = 0)** set an offset to calibrate the sensor (1st order).
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Default offset is 0.
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- **float getHumOffset()** return current humidity offset, default 0.
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- **void setTempOffset(float offset = 0)** set an offset to calibrate the sensor (1st order).
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Default offset is 0.
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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 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 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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- **int requestData()** signals the sensor to make a new measurement.
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Note there must be at least 1000 milliseconds between requests!
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- **int readData()** does the actual reading of the data.
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- **int convert()** converts the read bits to temperature and humidity.
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See the example **AM2315C_async.ino**
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#### Status
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- **uint8_t readStatus()** forced read of the status only.
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This function blocks a few milliseconds to optimize communication.
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- **bool isCalibrated()** idem, wrapper around **readStatus()**
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- **bool isMeasuring()** idem, wrapper around **readStatus()**
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- **bool isIdle()** idem, wrapper around **readStatus()**
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- **int internalStatus()** returns the internal status of the sensor. (for debug).
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| status bit | meaning |
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|:------------:|:---------------------------|
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| 7 | 1 = measurement, 0 = idle |
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| 6 - 4 | unknown |
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| 3 | 1 = calibrated, 0 = not |
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| 2 - 0 | unknown |
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#### Experimental resetSensor
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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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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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- **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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#### Return codes
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| name | value | notes |
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|:-------------------------------|:-------:|:--------|
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| AM2315C_OK | 00 | OK
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| AM2315C_ERROR_CHECKSUM | -10 | values might be OK if they are like recent previous ones.
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| AM2315C_ERROR_CONNECT | -11 | check connection
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| AM2315C_MISSING_BYTES | -12 | check connection
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| AM2315C_ERROR_BYTES_ALL_ZERO | -13 | check connection
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| AM2315C_ERROR_READ_TIMEOUT | -14 |
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| AM2315C_ERROR_LASTREAD | -15 | wait 1 second between reads
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## Future
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#### Must
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- improve documentation.
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- follow / sync DHT20 developments
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- see https://github.com/RobTillaart/DHT20
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- get hardware / sensor to test library
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#### Should
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#### Could
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#### Wont
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## Support
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If you appreciate my libraries, you can support the development and maintenance.
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Improve the quality of the libraries by providing issues and Pull Requests, or
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donate through PayPal or GitHub sponsors.
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Thank you,
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