Arduino library for AM2320 AM2321 and AM2322 I2C temperature and humidity sensor.
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.
This library works also for the AM2315 which has a library of its own - https://github.com/RobTillaart/AM2315
| 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.
The datasheet states the AM2320 should be used on 100 KHz I2C only.
TODO measure and verify (see AM2315)
The AM2320, AM2321 and AM2322 can also be read by using a "OneWire" protocol. This protocol is identical to the DHT22 and will only provide temperature, humidity and a CRC. See issue #26.
If one wants to use this protocol, one can use https://github.com/RobTillaart/DHTNew and optionally force the type to 22.
If problems arise with the "OneWire" protocol, please let me know and file the issues under DHTNew.
#include "AM232X.h"Since 0.4.2 the library provides specific classes for the AM2320, AM2321 and AM2322 which have the same interface.
- AM232X(TwoWire *wire = &Wire) constructor, default using Wire (I2C bus), optionally set to Wire0 .. WireN.
- bool begin() initializer for class. Returns true if fixed device address 0x5C is connected.
- bool isConnected(uint16_t timeout = 3000) returns true if the fixed device address 0x5C 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.
- int read() read the sensor and store the values internally. Returns the status of the read which should be AM232X_OK == 0.
- float getHumidity() returns the last read humidity + optional offset, or AM232X_INVALID_VALUE == -999 in case of error. This error can be suppressed, see below.
- float getTemperature() returns the last read temperature + optional offset, or AM232X_INVALID_VALUE == -999 in case of error. This error can be suppressed, see below.
- uint32_t lastRead() returns the timestamp in milliseconds since startup of the last successful read.
- void setHumOffset(float offset = 0) set an offset for humidity to calibrate (1st order) the sensor. Default offset = 0, so no parameter will reset the offset to 0.
- float getHumOffset() return the current humidity offset, default 0.
- void setTempOffset(float offset = 0) set an offset for temperature to calibrate (1st order) the sensor. Default offset = 0, so no parameter will reset the offset to 0.
- float getTempOffset() return the current temperature offset, default 0.
Functions to adjust the communication with the sensor.
- void setReadDelay(uint16_t readDelay = 0) Tunes the time it waits before actual read can be done. Set readDelay to 0 will reset it to 2000 ms effective the next read().
- uint16_t getReadDelay() returns the current readDelay in milliseconds. Note that a value of zero (reset) will return 0 before the call and 2000 after the call to read().
- bool wakeUp() function that will try for 3 milliseconds to wake up the sensor. This can be done before an actual read to minimize the read() call.
- void setSuppressError(bool b) suppress error values of AM232X_INVALID_VALUE == -999.
=> you need to check the return value of read() instead.
This can be used to keep spikes out of your graphs / logs. - bool getSuppressError() returns the current suppression setting.
Check datasheet for details.
- int getModel() idem
- int getVersion() idem
- uint32_t getDeviceID() idem
- int setStatus(uint8_t value)
- int getStatus()
Check datasheet for details.
- int setUserRegisterA(int value)
- int setUserRegisterB(int value)
- int getUserRegisterA()
- int getUserRegisterB()
| name | value | notes |
|---|---|---|
| AM232X_OK | 0 | |
| AM232X_ERROR_UNKNOWN | -10 | |
| AM232X_ERROR_CONNECT | -11 | |
| AM232X_ERROR_FUNCTION | -12 | |
| AM232X_ERROR_ADDRESS | -13 | |
| AM232X_ERROR_REGISTER | -14 | |
| AM232X_ERROR_CRC_1 | -15 | |
| AM232X_ERROR_CRC_2 | -16 | |
| AM232X_ERROR_WRITE_DISABLED | -17 | |
| AM232X_ERROR_WRITE_COUNT | -18 | |
| AM232X_MISSING_BYTES | -19 | |
| AM232X_READ_TOO_FAST | -20 | |
| AM232X_HUMIDITY_OUT_OF_RANGE | -100 | not used by default. |
| AM232X_TEMPERATURE_OUT_OF_RANGE | -101 | not used by default. |
| AM232X_INVALID_VALUE | -999 | can be suppressed. |
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(). Multiple calls will give the same values until read() is called again.
Note that the sensor can go into sleep mode after 3 seconds after last read, so one might need to call wakeUp() before the read().
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. you may use a PCF8574 to control the AND gates. https://github.com/RobTillaart/PCF8574
- Use a TCA9548A I2C Multiplexer, or similar. https://github.com/RobTillaart/TCA9548
Which method fit your application depends on your requirements and constraints.
- update documentation
- test more (other platforms)
- keep in sync with AM2315 class
- merge in a far future.
- update unit test
- add examples
- I2C performance measurements
- clock speed > 170 - see AM2315
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