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hts221

Connect to HTS221 sensor on Arduino hardware I2C bus

Description

The hts221 object reads relative humidity and ambient temperature using the HTS221 sensor connected to the I2C bus of the Arduino® hardware. HTS221 is used to read relative humidity. The HTS221 also has an embedded temperature sensor. Attach the HTS221 sensor to the I2C pins on the hardware. You can read the data from the sensor in MATLAB® using the Object Functions.

Creation

Description

humiditySensor = hts221(a) creates a sensor object with default property values.

Example: humiditySensor = hts221(a);.

humiditySensor = hts221(a,Name,Value) creates a sensor object with properties using one or more Name,Value pair arguments.

Example: humiditySensor = hts221(a, 'Bus', 1);.

Input Arguments

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Connection to the hardware specified as an object.

Example: humiditySensor = hts221(a) creates a connection to the HTS221 sensor on the hardware represented as an object, a.

Properties

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Note

The properties can also be used as name-value pair arguments while creating an hts221 object.

I2C bus number, specified as 0 or 1. The default value is 0.

Data Types: double

Note

The properties SampleRate, SamplesPerRead, ReadMode, OutputFormat, TimeFormat, SamplesAvailable, and SamplesRead are available only with the Sensor Fusion and Tracking Toolbox™ and Navigation Toolbox™. These properties can be set while you create the sensor object.

Except for TimeFormat, all the other properties are non-tunable, which means you cannot change their values once the object is locked. Objects are locked when you call the read function, and the release function unlocks them. If a property is tunable, you can change its value at any time.

The rate in samples/s at which data is read from the sensor.

Data Types: double

Number of samples read from the sensor in a single execution of the read function.

Data Types: double

Specify whether to return the latest or the oldest data samples. The number of samples depends on the SamplesPerRead value. The data read from the sensor is stored in the MATLAB buffer.

  • latest

    Provides the latest data samples available in the buffer. All previous data samples in the buffer are discarded. For example, if SamplesPerRead = 3, the latest three data samples read by the sensor are returned.

    The following figure illustrates how latest data samples are returned assuming S1 is the first sensor data stored in the buffer, S2 is the second data and so on and Sn is the last data stored in the buffer and SamplesPerRead property is set to 3 during sensor object creation.

  • oldest

    Provides the oldest data samples available in the buffer. In this case, no data samples are discarded. For example, if SamplesPerRead = 3, the first three data samples read are returned for the first read, the next three data samples are returned for the second read, and so on.

    The following figure illustrates how oldest data samples are returned assuming S1 is the first sensor data stored in the buffer, S2 is the second data and so on and Sn is the last data stored in the buffer and SamplesPerRead property is set to 3 during sensor object creation.

Data Types: character vector | string

This property is read-only.

Samplesread property outputs the values of samples read so far by executing read function. Samplesread is set to 0, when the object is created or when you release the object.

Data Types: double

Set the output format of the data returned by executing the read function.

When the OutputFormat is set to timetable, the data returned has the following fields:

  • Time — Time stamps in datetime or duration format

  • Humidity — N-by-1 array in units of %

  • Temperature — N-by-1 array in units of degree Celsius

When the OutputFormat is set to matrix, the data is returned as matrices of humidity, temperature, and time stamps. The units for the sensor readings are the same as the timetable format.

N is the number of samples per read specified by SamplesPerRead.

Data Types: character vector | string

Set the format of the time displayed when the sensor data is read.

  • datetime — Displays the date and time at which the data is read.

  • duration — Displays the time elapsed in seconds after the sensor object is locked. The sensor object gets locked at the first call of the read function either after the object creation or after the execution of the release function.

Data Types: character vector | string

Object Functions

readHumidityRead one sample of relative humidity data from the sensor
readTemperatureRead one sample of temperature from sensor
readRead real-time sensor data at a specified rate using Sensor Fusion and Tracking Toolbox or Navigation Toolbox
releaseRelease the sensor object
flushFlush the host buffer
infoRead information related to sensor

Examples

Create Connection to HTS221 Sensor

Create an arduino object with the I2C library.

a = arduino('COM4', 'Uno', 'Libraries', 'I2C');

Create the sensor object.

humiditySensor = hts221(a)
humiditySensor =
 
  hts221 with properties:
 
                         I2CAddress: 95  ("0x5F")
                                Bus: 0
                             SCLPin: "A5"
                             SDAPin: "A4"
 
Show all properties all functions

Create HTS221 Sensor Connection (with Sensor Fusion and Tracking Toolbox or Navigation Toolbox)

Create a sensor object with properties available only with the Sensor Fusion and Tracking Toolbox or Navigation Toolbox.

clear humiditySensor;
humiditySensor = hts221(a,'SampleRate',50,'SamplesPerRead',5,'ReadMode','Latest')
humiditySensor = 

  hts221 with properties: 

                 I2CAddress: 95  ("0x5F") 
                        Bus: 0
                     SCLPin: "A5" 
                     SDAPin: "A4" 

                 SampleRate: 50  (Samples/s)
             SamplesPerRead: 5  
                   ReadMode: 'latest'            
                SamplesRead: 0      
           SamplesAvailable: 0 

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More About

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See Also

Introduced in R2021a