Testing different methods to interface with a MPU-6050 or MPU-9250 via I2C. All methods feature the extraction of the raw sensor values as well as the implementation of a complementary filter for the fusion of the gyroscope and accelerometer to yield an angle(s) in 3 dimensional space.
Values retrieved below come from the MPU-6050 and MPU-9250 registry maps and product specifications documents located in the \Resources folder. Configure the gyroscope on 0x1B and the accelerometer on 0x1C as per data sheets with the following values (the MPU-6050 and MPU-9250 are interchangeable and all registries are the same):
| Accelerometer | Sensitivity | Gyroscope | Sensitivity | Hexadecimal | Binary |
|---|---|---|---|---|---|
| +/- 2g | 16384 | +/- 250 deg/s | 131 | 0x00 | 00000000 |
| +/- 4g | 8192 | +/- 500 deg/s | 65.5 | 0x08 | 00001000 |
| +/- 8g | 4096 | +/- 1000 deg/s | 32.8 | 0x10 | 00010000 |
| +/- 16g | 2048 | +/- 2000 deg/s | 16.4 | 0x18 | 00011000 |
The slave address is b110100X which is 7 bits long. The LSB bit of the 7 bit address is determined by the logic level on pin AD0. This allows two sensors to be connected to the same I2C bus. When used in this configuration, the address of one of the devices should be b1101000 (pin AD0 is logic low) and the address of the other should be b1101001 (pin AD0 is logic high). Communication will typically take place over the 0x68 register.
Ensure that the proper logic (3.3V vs 5V) is being used so you do not fry your sensor
Connect the sensor to the microcontroller as outlined below.
- VCC --> 5V or 3.3V based on specific breakout board and logic levels
- GND --> GND
- SDA and SCL pins located in table below:
| Board | SDA Pin | SCL Pin |
|---|---|---|
| Uno | A4 | A5 |
| Mega2560 | 20 | 21 |
| Leonardo | 2 | 3 |
| Due | 20 | 21 |
Upload the main.ino sketch and observe the values in the serial port or serial plotter. The calibrateGyro.ino sketch can be used to retrieve the offset values which can be directly placed into the main.ino sketch to eliminate the need for calibration every time the microcontroller is started up. Note that this is at at the cost of performance as the sensors drift over time and between uses.
Connect an Arduino using the same wiring as outlined above. Run MATLAB\I2C\main.m and observe the values in the command line. MATLAB is extremely slow when using an Arduino/I2C connection.
A faster method is to read data through a serial connection. Using the same wiring connection, upload the sketch in Visualizer\arduinoSketch to the Arduino board. Adjust any desired parameters as outlined below in the MATLAB\serial\main.m file. Run and observe the values in the command line.
% Set up the class
gyro = 250; % 250, 500, 1000, 2000 [deg/s]
acc = 2; % 2, 4, 7, 16 [g]
tau = 0.98; % Time constant
port = '/dev/cu.usbmodem14101'; % Serial port name
Connect your IMU sensor to 5V or 3.3V based on specific breakout board and ground to ground. Refer to the pinout of your board using pinout.xyz and match SDA and SCL accordingly.
Setup as described here. First enter sudo raspi-config and enable SPI and I2C. Reboot the Pi.
Edit the modules file using sudo nano /etc/modules and ensure i2c-bcm2708 and i2c-dev are both in the file. Reboot again.
With the sensor correctly wired enter the following in the command line.
sudo apt-get install i2c-tools python-smbus
sudo i2cdetect -y 1
Which should yield the table below (possible to have the value 0x69) verifying a proper connection:
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- 68 -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --
Once verified run python3 main.py to observe the values.
Follow the same setup guide as in the RPi (Python) section, however an MPU-9250 must be used.
The code is based on Kriswiner's C++ MPU-9250 library located here and Sebastian Madgwick's open source IMU and AHRS algorithms located here. To run the program navigate to the \9DOF directory and run python3 main.py.
Before running the program and sensor fusion algorithms the magnetometer must be calibrated. Uncomment the second line below and the program will walk you through all the required steps. Once values have been retrieved enter them in lines three and four below.
# Calibrate the mag or provide values that have been verified with the visualizer
# mpu.calibrateMagGuide()
bias = [282.893, 300.464, -91.72]
scale = [1.014, 1.054, 0.939]
mpu.setMagCalibration(bias, scale)
To verify the results of the calibration refer to the two articles located here and here. Place the values from the calibration into data.txt and magCalVisualizer.py and magCalSlider.py as described in the program guide during calibration. The magCalVisualizer.py and magCalSlider.py script will provide all the required plots to aid in verifying the results as well as interactive sliders to optimize values.
Connect an IMU device as outlined in the Arduino section. Upload the sketch located in Visualizer/arduinoSketch. This sketch simply transmits the raw byte data from the sensor over a serial connection.
Next, perform the following commands to add the necessary server which makes a bridge between the microcontroller and web application.
cd MPU-6050-9250-I2C-CompFilter/
git submodule add https://github.com/vanevery/p5.serialport.git Visualizer/p5js/server
cd Visualizer/p5js/server/
npm install
Edit the file sketch.js file located in Visualizer/p5js/main to set the desired properties and correct serial port.
// Customize these values
var portName = '/dev/cu.usbmodem14101';
var tau = 0.98;
var gyroScaleFactor = 65.5;
var accScaleFactor = 8192.0;
var calibrationPts = 100;
Once all the values are customized start the serial port server by navigating to Visualizer/p5js/server/ and entering:
node startserver.js
Double click on the index.html file located in Visualizer/p5js/main and the program will begin in your default browser. Alternatively you can enter the file path in a browser as such file:///Users/MarkSherstan/Documents/GitHub/MPU-6050-9250-I2C-CompFilter/Visualizer/p5js/main/index.html
Ensure to hold the IMU device still until an object appears on the screen. This is the program performing a calibration for gyroscope offset.
- RPi C++ Version
- Add quaternion angle representation
- Stat analysis for mag calibration (9DOF)
- Detailed accelerometer and gyroscope calibration(s)