MPU6050

Arduino library for the MPU6050 accelerometer and gyroscope sensor with I2C interface from InvenSense.

Introduction

The MPU6050 is a motion tracking device from InvenSense. It is I2C controlled, contains a 3-axis gyroscope and a 3-axis Accelerometer (and a thermometer). InvenSense has published a datasheet but for driver development, the register map is also crucial.

Background

An accelerometer is a device that measures acceleration. For example, an accelerometer at rest on the surface of the Earth will measure an acceleration due to Earth's gravity of g ≈ 9.81 m/s². In a typical implementation a mass is hung with one degree of freedom; it moves due to acceleration. The displacement (u) of the mass is linear with the force (F/u=C) on it, so displacement gives force (F). The force (F) is linear with the acceleration (F=m×a), so the force gives the acceleration (a). Integrating acceleration in time gives speed (v) and integrating speed in time gives traveled distance. Accelerometers are used in mobile phones and digital cameras so that images on screens are always displayed upright. Accelerometers are used in drones for flight stabilisation and for drop detection.

A gyroscope is a device used for measuring or maintaining orientation. A typical implementation is a spinning wheel in which the axis of rotation is free to assume any orientation by itself. Applications of gyroscopes include navigation systems.

Gyroscope suffer from drift; accelerometers are used to compensate for that.

Acknowledgements

This project was built upon

• Simple-MPU6050-Arduino
• Direction
• NXP app note

This project

This project implements an Arduino library for the MPU6050. It comes with some examples.

Note that the MPU6050 requires a supply voltage of 3.3V. So, Arduino's 5.0V is not OK. However, some boards, like the GY521 have an on-board voltage regulator and level shifter.

Getting started

These steps are discussed in details below

• Hardware: make sure you have a microcontroller and a sensor, and wire them together
• Software: make sure you have the Arduino IDE and install this library
• Example: open, compile, flash and run one of the library examples

Hardware

The hardware steps to take

• You need an Arduino, e.g. an Arduino Nano. I got a cheap clone with a USB micro plug.
• You need an MPU6050. I got a GY521 breakout board with a 5V to 3V regulator.
• You need to connect them. This library is simple; it only uses the I2C lines. So 4 wires are needed. I did not add pull-ups, the ones inside the Nano appear sufficient.

Software

The software steps to take

• It is assumed that you have the Arduino IDE installed. If not, refer to "Install the Arduino Desktop IDE" on the Arduino site. If you follow the default install, libraries will install here C:\Users\maarten\Documents\Arduino\libraries (for me, Maarten).
• Install this library
  • Visit the project page for the Arduino MPU6050 library.
  • Click the green button Clone or download on the right side, and from the pop-up choose Download ZIP.
  • Start Arduino, select from menu Sketch > Include Library > Add .ZIP Library... and select the just downloaded ZIP file.
  • An alternative to the last step is to manually add the library: Unzip the file "Here", and copy the entire tree to the Arduino library directory. This README.md should be located at e.g. C:\Users\maarten\Documents\Arduino\libraries\MPU6050\README.md.
• Somehow, I have quite some I2C trouble (communication errors) between the Nano and the MPU6050. Unfortunately, some of the issues cause the Nano I2C library to hang: there is a while loop without time-out. If you suffer from I2C hangs, you could consider adding the timeout patch.

Example

Running the example

• Restart the Arduino IDE and Open File > Example > Examples from Custom Libraries > MPU6050 > basic.
• Make sure Tools > Board has Arduino Nano, Tools > Processor has the right bootloader (old for me), and Tools > Port has the correct COM port.
• Select Sketch > Upload to compile and upload the example to the Nano.
• Open the Tools > Serial Monitor (at 115200 baud) and see the output

Welcome to the MPU6050 basic example
Driver version 1.0
MPU6050: sensor is ... present
MPU6050: success
 ae=0 ax=0.28 ay=-0.23 az=9.67 / ge=0 gx=0.05 gy=0.07 gz=0.00 / de=0 dx=0.23 dy=0.33 dz=0.01 / te=0 tt=23.35
 ae=0 ax=0.29 ay=-0.20 az=9.67 / ge=0 gx=0.15 gy=-0.01 gz=-0.07 / de=0 dx=0.23 dy=0.33 dz=0.01 / te=0 tt=23.35
 ae=0 ax=0.24 ay=-0.23 az=9.73 / ge=0 gx=0.09 gy=0.08 gz=-0.06 / de=0 dx=0.23 dy=0.34 dz=0.01 / te=0 tt=23.31
 ae=0 ax=0.28 ay=-0.26 az=9.73 / ge=0 gx=-0.04 gy=0.03 gz=0.06 / de=0 dx=0.22 dy=0.33 dz=0.01 / te=0 tt=23.35
 ae=0 ax=0.28 ay=-0.23 az=9.68 / ge=0 gx=0.07 gy=0.08 gz=-0.02 / de=0 dx=0.23 dy=0.33 dz=0.01 / te=0 tt=23.31
 ae=0 ax=0.28 ay=-0.19 az=9.69 / ge=0 gx=0.07 gy=-0.06 gz=0.06 / de=0 dx=0.24 dy=0.33 dz=0.01 / te=0 tt=23.26
 ae=0 ax=0.22 ay=-0.26 az=9.65 / ge=0 gx=0.03 gy=0.02 gz=-0.14 / de=0 dx=0.22 dy=0.35 dz=0.01 / te=0 tt=23.21
 ae=0 ax=0.26 ay=-0.25 az=9.69 / ge=0 gx=-0.08 gy=0.20 gz=0.14 / de=0 dx=0.22 dy=0.34 dz=0.01 / te=0 tt=23.35
 ae=0 ax=0.29 ay=-0.28 az=9.61 / ge=0 gx=-0.04 gy=-0.12 gz=-0.07 / de=0 dx=0.22 dy=0.33 dz=0.01 / te=0 tt=23.40
 ae=0 ax=0.26 ay=-0.26 az=9.67 / ge=0 gx=0.02 gy=-0.04 gz=-0.04 / de=0 dx=0.22 dy=0.34 dz=0.01 / te=0 tt=23.45
 ae=0 ax=0.21 ay=-0.26 az=9.59 / ge=0 gx=-0.05 gy=0.03 gz=0.07 / de=0 dx=0.22 dy=0.35 dz=0.01 / te=0 tt=23.45
 ae=0 ax=0.24 ay=-0.27 az=9.66 / ge=0 gx=0.00 gy=0.00 gz=0.13 / de=0 dx=0.22 dy=0.34 dz=0.01 / te=0 tt=23.40
 ae=0 ax=0.26 ay=-0.25 az=9.61 / ge=0 gx=0.02 gy=-0.01 gz=-0.13 / de=0 dx=0.22 dy=0.34 dz=0.01 / te=0 tt=23.31
 ae=0 ax=0.29 ay=-0.24 az=9.67 / ge=0 gx=0.07 gy=0.12 gz=-0.09 / de=0 dx=0.23 dy=0.33 dz=0.01 / te=0 tt=23.31

Notes on the example

• On the first line see a general banner for the example application
• On the second line see the actual version of this library (yours might be newer)
• On the third line, the application checks if the MPU6050 is present (correctly connected). Unfortunately, the Arduino I2C library does not feature a time-out (or a very long one) when an I2C device is not responding. So if it takes "forever" for the present to appear, you likely have a connection problem.
• The next line (with success) gives the status of the MPU6050.begin() call. This call wakes-up the device, configures it, calibrates it. If it does not say success you have a problem.
• Every next lines show feedback from one measurement, showing details of the 4 sensors inside the MPU6050.
• The first block shows the accelerator data.
  • ae should be 0, otherwise there was an I2C error when reading the accelerator data.
  • ax is the acceleration in x-direction (in m/s²).
  • similarly ay and az are the acceleration in y-direction respectively z-direction.
  • note that indeed az is about 9.81, earth's gravity.
• The second block shows the gyroscope data.
  • ge should be 0, otherwise there was an I2C error when reading the gyroscope data.
  • gx is the angular rate in x-direction (in °/sec).
  • similarly gy and gz are the angular rate in y-direction respectively z-direction.
  • note that all these are typical 0 (they are calibrated to be 0) as long as the sensor is stationary.
• The third block is computed from the previous two. It computes the roll, pitch, and yaw direction.
  • de should be 0, otherwise there was an I2C error when reading the accelerometer or gyroscope data.
  • dx is the pitch (in °).
  • similarly dy and dz are the roll and yaw.
  • note that all these are typical 0 (calibrated to be) as long as the sensor is stationary.
• The fourth block shows the temperature data.
  • te should be 0, otherwise there was an I2C error when reading the temperature data.
  • tt is the temperature (in °C).

Other examples

There are also three use-case examples.

The Rotate example shows how to keep track of your direction. For example in a robot with two independent (left and right) motors, it is hard to drive straight: the motors in practive have different speeds and different slip.

.

The Shake example shows how to detect shaking the sensor, by just looking at the accelorator data.

The most elaborate example is PID. It uses a PID controller to go straight. See this video for a demo. Or this one where the robot runs in "squares".

(end of doc)