AM232X

Arduino library for AM2320 AM2321 and AM2322 I2C temperature and humidity sensor.

Description

AM232X is a sensor similar to the DHT12 with an I2C interface. Although in theory this could enable multiple sensors on one bus the AM232X has a fixed address 0x5C so one need to implement a multiplexing strategy to have multiple sensors in practice. See multiplexing below.

Typical parameters

	range	accuracy	repeatability
Temperature	-40 - 80	0.5°C	±0.1
Humidity	0.0 - 99.9	3%	±0.1
Sample time	2 seconds

//  AM232X PIN layout             AM2315 COLOR
//  ============================================
//   bottom view  DESCRIPTION     COLOR
//       +---+
//       |o  |       VDD          RED
//       |o  |       SDA          YELLOW
//       |o  |       GND          BLACK
//       |o  |       SCL          GREY
//       +---+
//
// do not forget pull up resistors between SDA, SCL and VDD.

Interface

Constructor

AM232X(TwoWire *wire = &Wire) constructor, optionally set Wire0..WireN.
bool begin(uint8_t sda, uint8_t scl) for ESP32 alike devices, returns true if device is connected.
bool begin() for AVR alike devices, returns true if device is connected.
bool isConnected(uint16_t timeout = 3000) returns true if device-address is found on I2C bus. As the device can be in sleep modus it will retry for the defined timeout (in micros) with a minimum of 1 try. minimum = 800 us and maximum = 3000 us according to datasheet.

Base calls

int read() fetches the values from the sensor.
uint32_t lastRead() returns milliseconds since start of last read.
float getHumidity() returns the last read humidity.
float getTemperature() returns the last read temperature.

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.

Control

Functions to adjust the interval time the sensor may be called again. Default = 2000 ms (from datasheet).

void setReadDelay(uint16_t rd = 0) Tunes the time it waits before actual read can be done. Set readDelay to 0 will reset it to 2000 ms after a call to read().
uint16_t getReadDelay() returns the above setting. Note that a value of zero (reset) will return 0 before the call and 2000 after the call to read().

Misc

check datasheet for details.

int getModel() idem
int getVersion() idem
uint32_t getDeviceID() idem
int getStatus()
int getUserRegisterA()
int getUserRegisterB()
int setStatus(uint8_t value)
int setUserRegisterA(int value)
int setUserRegisterB(int value)
bool wakeUp() function that will try for 3 milliseconds to wake up the sensor.

Operation

See examples

In setup() you have to call the begin() to initialize the Wire library and do an initial read() to fill the variables temperature and humidity. To access these values one must use getTemperature() and getHumidity().

Note that the sensor can go into sleep mode and one might need to call wakeUp() before the read().

Multiplexing

Multiplexing the AM232X can be done in several ways. This is not a complete list or tutorial but should get you started.

Control the power line by means of an extra pin (+ transistor). Only switch on the sensor you want to use. Drawback might be time the sensor takes to boot and to be ready for the first measurement.
Use an AND gate between the I2C SCL (clock) line and the I2C SCL pin of the sensors. This way one can enable / disable communication per sensor. This will still need an IO pin per sensor but does not have the "boot time" constraint mentioned above.
Use a TCA9548A I2C Multiplexer, or similar. https://github.com/RobTillaart/TCA9548

Which method fit your application depends on your requirements and constraints.

Warning

The library has not been tested extensively yet so use at own risk.

Future

update documentation
test more
add specific named classes ?
- AM2320, AM2321, AM2322 ?
- AM2315 - add type field ?

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