mpu9250

Connect to MPU-9250 sensor on Arduino hardware I2C bus

Description

The mpu9250 object reads acceleration, angular velocity, and magnetic field using the InvenSense MPU-9250 sensor. The MPU-9250 is a 9 degree of freedom (DOF) inertial measurement unit (IMU) used to read acceleration, angular velocity, and magnetic field in all three dimensions.

The mpu9250 object represents a connection to the device on the Arduino^® hardware I2C bus. Attach an MPU-9250 sensor to the I2C pins on the Arduino hardware. You can read the data from your sensor in MATLAB^®using the object functions.

Before you use the mpu9250 object, create an Arduino object using arduino and set its properties. When you create the Arduino object, make sure that you include the I2C library. For more information, see Connect to Arduino Hardware.

Creation

Syntax

imu = mpu9250(a)

imu = mpu9250(a,Name,Value)

Description

imu = mpu9250(a) creates a sensor object with default property values. The object represents the connection to the sensor on the Arduino hardware, a.

imu = mpu9250(a,Name,Value) creates a sensor object with properties using one or more Name,Value pair arguments.

Input Arguments

a — Arduino hardware connection

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

Example: imu = mpu9250(a) creates a connection to the MPU-9250 sensor on the Arduino object, a.

Name-Value Pair Arguments

Specify optional comma-separated pairs of Name,Value arguments. Name is the argument name and Value is the corresponding value. Name must appear inside quotes. You can specify several name and value pair arguments in any order as Name1,Value1,...,NameN,ValueN.

'I2CAddress' — Specify I2C address of sensor

[0x68, 0x0C] | [0x69, 0x0C]

Specify the I2C address of the sensors when multiple I2C devices with the expected address for MPU9250 are connected to the same hardware board. MPU9250 can have multiple I2C addresses depending on the logic level on pin AD0 of the sensor.

Pin Name	Pin State	I2C Address
AD0	Low	[0x68, 0x0C]
	High	[0x69, 0x0C]

You can specify the I2C address in:

• Numeric array of hexadecimal, decimal, or binary format of I2C Addresses

• String array of hexadecimal value of I2C Addresses

• Cell array of character vector of hexadecimal value of I2C Addresses

Example: imu = mpu9250(a,'I2CAddress',[0x68, 0x0C])

'0x69' is the I2C address of the accelerometer and gyroscope of MPU9250. '0x0C' is the I2C address of the magnetometer of MPU9250.

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.

'Bus' — I2C Bus Number

0 (default) | 1

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

Example: imu = mpu9250(a, 'Bus', 1) creates the sensor object on Bus 1 of Arduino Due board

Data Types: double

Properties

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.

SampleRate — Rate at which sample is read

100 (default) | positive integer in the range [11, 200]

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

Tunable: No

Data Types: double

SamplesPerRead — Number of samples read in a single execution of the read function

10 (default) | [1 500]

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

Tunable: No

Data Types: double

ReadMode — Specify which data samples to be returned

'latest' (default) | 'oldest'

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.

  

Tunable: No

Data Types: character vector | string

SamplesRead — Samples read

double

This property is read-only.

Samples read from the first read. When you release the object, SamplesRead is set to 0.

Data Types: double

SamplesAvailable — Samples in the host buffer

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

OutputFormat — Set output format

'timetable' (default) | 'matrix'

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

• AngularVelocity — N-by-3 array in units of rad/s

• MagneticField — N-by-3 array in units of µT (microtesla)

When the OutputFormat is set to matrix, the data is returned as matrices of acceleration, angular velocity, magnetic field, and time stamps. The units for the sensor readings are the same as the timetable format. The size of each matrix is N-by-3.

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.

Tunable: No

Data Types: character vector | string

TimeFormat — Set time format

'datetime' (default) | 'duration'

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 sesnor object gets locked at the first call of the read function either after the object creation or after the execution of the release function.

Tunable: Yes

Data Types: character vector | string

Usage

Create MPU-9250 Sensor Connection

Create an Arduino object and include the I2C library.

a = arduino();

Or, you can explicitly specify it in the Libraries Name-Value pair while creating the Arduino object.

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

Create the sensor object.

imu = mpu9250(a)

imu = 

  mpu9250 with properties: 

                 I2CAddress: 104  ("0x68")
                           : 12   ("0xC")
                     SCLPin: "A5" 
                     SDAPin: "A4" 

      

Create MPU-9250 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 imu;
imu = mpu9250(a,'SampleRate',50,'SamplesPerRead',5,'ReadMode','Latest')

imu = 

  mpu9250 with properties: 

                 I2CAddress: 104  ("0x68")
                           : 12   ("0xC")
                     SCLPin: "A5" 
                     SDAPin: "A4" 

                 SampleRate: 50  (Samples/s)
             SamplesPerRead: 5  
                   ReadMode: 'latest'            
                SamplesRead: 0      
           SamplesAvailable: 0 
Show all properties, functions
 

Object Functions

readAcceleration	Read one sample of acceleration from sensor
readAngularVelocity	Read one sample of angular velocity from sensor
readMagneticField	Read one sample of magnetic field from sensor
read	Read real-time sensor data at a specified rate using Sensor Fusion and Tracking Toolbox or Navigation Toolbox
release	Release the sensor object
flush	Flush the host buffer
info	Read information related to sensor

More About

Code Generation Using MATLAB Function Block

• Use mpu9250 in a MATLAB Function block with the Simulink^® Support Package for Arduino Hardware to generate code that can be deployed on Arduino Hardware.

• The property ReadMode cannot be changed and is always set to latest.

• The property SamplesPerRead cannot be changed and is always set to 1. So, no framing is provided.

• The property OutputFormat is always set to matrix.

• The property TimeFormat is always set to duration.

• The property SamplesAvailable is not accessible from sensor object.

• The default value of I2C address will be taken as [0x68, 0x0C]. Specify I2C address if the sensor has a different I2C address. The possible values of I2C Addresses are mentioned in the table under I2Caddress section in this page.