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adxl345

Connect to ADXL345, ADXL343, ADXL344, or ADXL346 sensor on Arduino hardware I2C bus

Since R2022a

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Add-On Required: This feature requires the MATLAB Support Package for Arduino Hardware add-on.

Description

The adxl345 object reads linear acceleration using the ADXL345, ADXL343, ADXL344, or ADXL346 sensor connected to the I2C bus of the hardware. The ADXL34x family of accelerometers are used to read acceleration in all three dimensions. Attach an ADXL34x sensor to the I2C pins on the hardware. You can read the data from your sensor in MATLAB® using the Object Functions.

Creation

Syntax

accelSensor = adxl345(a)
accelSensor = adxl345(a,Name,Value)

Description

accelSensor = adxl345(a) creates a sensor object with default property values.

Example: accelSensor = adxl345(a);.

accelSensor = adxl345(a,Name,Value) creates a sensor object with properties using one or more Name,Value pair arguments.

Example: accelSensor = adxl345(a, Bus=1);.

Input Arguments

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Arduino hardware connection created using arduino, specified as an object.

Example: accelSensor = adxl345(a) creates a connection to the ADXL345 sensor on the Arduino hardware represented as an object, a.

Name-Value Arguments

Specify optional pairs of arguments as Name1=Value1,...,NameN=ValueN, where Name is the argument name and Value is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.

Example: accelSensor = adxl345(a,Bus=1);

You can specify any of the properties on this page as name-value pairs

Properties

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Note

  • All the properties except SamplesRead and SamplesAvailable can be set by specifying as name-value pair arguments while creating an adxl345 object.

  • The properties I2CAddress and Bus are immutable (the property value is set during construction; you cannot change the value of an immutable property after the object is created).

  • The TimeFormat property is tunable, which means you can change the value anytime. The SampleRate, SamplesPerRead, ReadMode, and OutputFormat 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.

Specify the I2C address of the sensors when multiple I2C devices with the expected address for ADXL34x are connected to the same hardware board. ADXL34x can have two I2C addresses depending on the logic level on pin SA0 of the sensor.

Pin NamePin StateI2C Address
ALTLow0x53
High0x1D

You can specify the I2C address in:

  • Hexadecimal, decimal, or binary format

  • String of hexadecimal value of I2C Address

  • Character vector of hexadecimal value of I2C Address

0x53 is the I2C address of the ADXL345 connected to Arduino board.

If not specified, the object will be created with one of the available I2C device address in the table. Availability of I2C device with the expected address will be determined by using scanI2CBus.

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

Data Types: double

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

This property is read-only.

Samples available in the host buffer. The data read from the sensor is stored in the MATLAB buffer. SamplesAvailable property shows the number of SamplesAvailable in this host buffer. When you release the object, SamplesAvailable is set to 0. When the ReadMode of sensor is set as latest, SamplesAvailable will always be 0.

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

  • Acceleration — N-by-3 array in units of m/s2

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

N is the number of samples per read specified by SamplesPerRead. The three columns of each field represent the measurements in x, y, and z axes.

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

readAccelerationRead one sample of acceleration from sensor
readRead real-time sensor data at a specified rate
releaseRelease the sensor object
flushFlush the host buffer
infoRead information related to sensor

Examples

Create Connection to ADXL345 Sensor

Create an arduino object with the I2C library.

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

Create the sensor object.

accelSensor = adxl345(a)
accelSensor = 

  adxl345 with properties:

                 I2CAddress: 83 ("0x53")
                        Bus: 0 
                     SCLPin: "A5" 
                     SDAPin: "A4" 

                 SampleRate: 100  (Samples/s)
             SamplesPerRead: 10  
                   ReadMode: 'latest'            
                SamplesRead: 0      
           SamplesAvailable: 0 

Show all properties, functions

Create ADXL345 Sensor Connection with Additional Name-Value Pair Arguments

Create a sensor object with additional properties specified as name-value pair arguments.

clear accelSensor;
accelSensor = adxl345(a,SampleRate=110,SamplesPerRead=3,ReadMode='latest')
imu =

  accelSensor with properties:

                         I2CAddress: 83 ("0x53")
                                Bus: 0
                             SCLPin: "A5"
                             SDAPin: "A4"

                         SampleRate: 110 (samples/s)
                     SamplesPerRead: 3
                           ReadMode: "latest"
                        SamplesRead: 0
                   SamplesAvailable: 0

Show all properties, functions

More About

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Version History

Introduced in R2022a

See Also

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