ESP32 with MPU9250 9-axis Gyro Accelerator Magnetometer Module

In this tutorial, we will learn to interface MPU9250 9-axis Gyro Accelerator Magnetometer Module with ESP32. Firstly, we will see the introduction of this 9-DOF MEMS sensor module, pinout, and specifications. In the end, we will see an example to measure 3-axis values of Gyro, Accelerator Magnetometer

We have a similar guide with Arduino:

• MPU9250 9-DOF Gyro Accelerator Magnetometer Module with Arduino

MPU9250 9-Axis Gyro Accelerator Magnetometer Module Introduction

MPU9250 is a multi-tasking sensor module based on MEMS (Micro Electro Mechanical Systems) architecture. It is a product by Asahi Kasei Microdevices Corporation. The MPU9250 is a 9-axial Motion Tracking device with a 3-Dimensional gyroscope, 3-Dimensional magnetometer, and 3-Dimensional accelerometer embedded into an ultra-compact IC. The high-performance IC has 16-bit resolution analog-to-digital Converters. The sensitive module also has a VDDIO, an inbuilt temperature sensor, and an auxiliary I2C interface data transmission with non-inertial sensors.

The 9-DOF Sensor module comes with an I2C interface with a data rate of 400 kHz. A Serial Peripheral Interface for fast mode with a rate of up to 20 MHz is provided in the module. It also has frame synchronization. The MPU9250 finds its applications in most of the intelligent electronics consumer products in one way or the other. Virtual Reality gaming is the perfect application of MPU9250 9-DOF MEMS Sensor module.

This tutorial will share the pin configuration, features, specification, interfacing, and applications.

MPU9250 Components

The MEMS Sensor module consists of MPU9250, I/O Headers, Pull-up Resistors, LDO, and Decoupling Capacitors.

MPU9250 chip: The IC is integrated with an accelerometer, gyroscope, and magnetometer and does all the processing.

I/O Headers: The headers will serve the purpose of connectivity and data transmission with the microcontroller unit.

Pull-up Resistors: The pull resistors are placed for I2C Bus to source current and establish a default state.

LDO: LDO voltage regulator is provided to reduce the voltage to 3.3V for the IC functioning and increase power efficiency.

Decoupling Capacitors: The decoupling capacitors remove the unwanted noise from the signals.

Internal Circuit Diagram

MPU9250 9-Axis Gyro Accelerator Magnetometer Module Pinout

The following diagram shows the pinout of the MPU 9250 9-DOF MEMS Sensor Module:

Pin Configuration

MPU9250 9-DOF MEMS Sensor Module has a total of 10 pins. The pin configuration detail in the tabular is mentioned below:

MPU9250 Features and Specifications

Following are some of the features of the MPU 9-DOF MEMS Sensor Module:

Detailed Features

Some of the useful features MPU 9-DOF MEMS Sensor Module are listed below:

• It has a triple-axis MEMS gyroscope, accelerometer, and magnetometer
•  Digital-output accelerometer full-scale range: ±2g, ±4g, ±8g, and ±16g
• Digital-output 3-Axis Gyroscope full-scale range:±250, ±500, ±1000, and ±2000°/sec
• Hall-effect Magnetometer full-scale measurement range: ±4800µT
• It comes with triple pair of three 16-bit Analog-to-Digital Converters
• The module has a user-programmable low-pass filter and wake-on-motion interrupt to operate in low power mode
• Gyroscope operating current: 3.2mA
• Accelerometer Operating current: 450µA
• Magnetometer Operating current: 280µA
•  Magnetometer Repetition Rate: 8Hz
• Sleep mode operating current: 8µA 
• Magnetometer output data resolution: 14-bit (0.6µT/LSB) 
• The module has I2C, SPI and an additional Auxiliary I2C interface.
• It is embedded with a Self-test function to diagnose the operations of the module to ensure its proper functioning.

MPU9250 Interfacing with ESP32

This section deals with the interfacing of an ESP32 to the MPU 9-DOF MEMS Sensor Module. MPU9250 9-DOF MEMS Sensor Module interfaces with any microcontroller using an I2C bus. In this section, we will see how to use MPU9250 with ESP32.

We will connect 4 pins of the MPU9250 sensor with ESP32. These include the VCC, GND, SCL, and SDA pins. The VCC will be connected with the 3.3V pin from the ESP32 board. GND of both the devices will be in common. The default I2C GPIO pins of ESP32 are being used to connect with each of the remaining I2C terminals of the MUP9250 module.

The figure below shows the default I2C pins of ESP32.

• GPIO21 is the default SDA pin.
• GPIO22 is the default SCL pin.

The table below shows the connections between ESP32 and MPU9250 sensors:

Now follow the connections between the two devices and connect them accordingly. We have used the same connections as specified above. All devices will have their grounds in common.

• Connect the power supply pins of the module to the ground and the 3.3 volts pin of the ESP32.
• Connect the SDA and SCL pins of the Sensor module to default I2C communication pins of ESP32
• Make sure to use long jumpers to avoid disturbance because we would rotate the module three-dimensionally to observe the result.

MPU9250 ESP32 Code

For the MPU9250 code for ESP32, we will use an Arduino library. First, let’s see how to install the MPU9250 library in Arduino IDE.

Install MPU9250 Library

First, download the MPU9250 and install it to the Arduino IDE. Restart the Arduino IDE. It is easy to use the library written specifically for the module. After installation, include the library to sketch the code. Download the zip file of MPU9250 then follow these steps to install the library: Sketch >Include Library> Add .ZIP Library.

To see the example codes follow these steps: File>Examples>MPU9250_Master.

The library has six example codes i.e.

• Advanced_I2C
• Basic_I2C
• FIFO_SPI
• Basic_SPI
• Interrupt_SPI
• WOM_I2C

Example I2C Sketch

#include "MPU9250.h"

// an MPU9250 object with the MPU-9250 sensor on I2C bus 0 with address 0x68
MPU9250 IMU(Wire, 0x68);
int status;

void setup() {
  // serial to display data
  Serial.begin(115200);
  while (!Serial) {}

  // start communication with IMU
  status = IMU.begin();
  if (status < 0) {
    Serial.println("IMU initialization unsuccessful");
    Serial.println("Check IMU wiring or try cycling power");
    Serial.print("Status: ");
    Serial.println(status);
    while (1) {}
  }
}

void loop() {
  // read the sensor
  IMU.readSensor();
  // display the data
  Serial.print(IMU.getAccelX_mss(), 6);
  Serial.print("\t");
  Serial.print(IMU.getAccelY_mss(), 6);
  Serial.print("\t");
  Serial.print(IMU.getAccelZ_mss(), 6);
  Serial.print("\t");
  Serial.print(IMU.getGyroX_rads(), 6);
  Serial.print("\t");
  Serial.print(IMU.getGyroY_rads(), 6);
  Serial.print("\t");
  Serial.print(IMU.getGyroZ_rads(), 6);
  Serial.print("\t");
  Serial.print(IMU.getMagX_uT(), 6);
  Serial.print("\t");
  Serial.print(IMU.getMagY_uT(), 6);
  Serial.print("\t");
  Serial.print(IMU.getMagZ_uT(), 6);
  Serial.print("\t");
  Serial.println(IMU.getTemperature_C(), 6);
  delay(100);
}

Code Explanation

Include Library

To program a code in Arduino IDE, the first is always to add the header files. Include the concerned header file, to interface the MPU9250 9-DOF MEMS Sensor Module to the ESP32. It has already written codes for reading the values of the accelerometer, gyroscope, and magnetometer. Through these inbuilt codes, it will take in, process, and output the acceleration, angle, and magnetic field to determine the position and orientation of the module.

#include "MPU9250.h"

IMU Object

An object “IMU” is created with an address i.e. 0x68 on the I2C Bus. It is done with the help of the MPU9250 sensor to store and act on the data and return the respective measurements.

// an MPU9250 object with the MPU-9250 sensor on I2C bus 0 with address 0x68
MPU9250 IMU(Wire, 0x68);

void Setup

The void setup block executes two conditions. First, it initializes the Serial monitor at a baud rate of 11520 bps. If the Serial monitor does not launch and no values are displayed then the execution cycle halts and the code will be stopped. Next a variable “status” is declared that checks the status of the IMU object. If the status is less than 0 i.e no voltage is received then the Serial monitor will display the messages “IMU initialization unsuccessful”, “Check IMU wiring or try cycling power” and then prints the value stored in status. As this is a forever condition because of the while(1) statement , the code will not go further unless the status value is greater than 0.

// serial to display data
  Serial.begin(115200);
  while (!Serial) {}

  // start communication with IMU
  status = IMU.begin();
  if (status < 0) {
    Serial.println("IMU initialization unsuccessful");
    Serial.println("Check IMU wiring or try cycling power");
    Serial.print("Status: ");
    Serial.println(status);
    while (1) {}
  }

void loop

The execution cycle enters the void loop block when the status of IMU is more than 0. The loop will read the IMU through readSensor(). They read the values of the accelerometer, gyroscope, and magnetometer.

The value of acceleration in mG in x-axis, y-axis and z-axis is read through getAccelX_mss(), getAccelY_mss() and getAccelZ_mss() respectively and displayed in Serial monitor. The value will be displayed upto 6 decimal places.

The measurement of angle in radians per second in x-axis, y-axis and z-axis is read through getGyroX_rads(), getGyroY_rads() and getGyroZ_rads() respectively and displayed in Serial monitor. The value will be displayed up to 6 decimal places as well.

Similarly, the value of magnetic field strength in Tesla in x-axis, y-axis and z-axis is read through getMagX_uT(), getMagY_uT() and getMagZ_uT() respectively and displayed in the Serial monitor. The value will also be displayed up to 6 decimal places.

Finally, it will get the value of temperature through getTemperature_C() up to 6 decimal places.

 // read the sensor
  IMU.readSensor();
  // display the data
  Serial.print(IMU.getAccelX_mss(), 6);
  Serial.print("\t");
  Serial.print(IMU.getAccelY_mss(), 6);
  Serial.print("\t");
  Serial.print(IMU.getAccelZ_mss(), 6);
  Serial.print("\t");
  Serial.print(IMU.getGyroX_rads(), 6);
  Serial.print("\t");
  Serial.print(IMU.getGyroY_rads(), 6);
  Serial.print("\t");
  Serial.print(IMU.getGyroZ_rads(), 6);
  Serial.print("\t");
  Serial.print(IMU.getMagX_uT(), 6);
  Serial.print("\t");
  Serial.print(IMU.getMagY_uT(), 6);
  Serial.print("\t");
  Serial.print(IMU.getMagZ_uT(), 6);
  Serial.print("\t");
  Serial.println(IMU.getTemperature_C(), 6);
  delay(100);

Upload the code to the ESP32. The MEMS Sensor module will take up the values. As soon as the Serial monitor is launched, the position and orientation is displayed like

•  “AccelX    AccelY:    AccelZ:    ”
•  “GyroX:    GyroY:    GyroZ:    ”
•  “MagX:    MagY:    MagZ:”
•  “Temperature in C:  ”

Rotate the sensor module in three dimensions as you like. The values at that particular time are shown on the Serial monitor. We can interface an LCD or an OLED to present the measurement. The example codes are flexible. They can be used as it or can be calibrated as per the requirement of the user.

 Alternate Options

• ADXL335
• MPU6050

Applications

• Joysticks controllers
• Medical Systems
• 3D remote controls
• Set top boxes
• Orientation Detection
• Wearable sensors for health, fitness and sports
• Location based services
• VR Gaming
• Robotics

2D Diagram

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