We have updated our git repository with python code for the BerryIMU.
This is specific for the BerryIMU, however the math and code can be applied to any digital IMU, just some minor modifications need to be made. E.g Pololu MinIMU, Adafruit IMU and Sparkfun IMUs
Git repository here The code can be pulled down to your Raspberry Pi with;
We have left the code as simple as it can be to make it easier to understand.
The code currently performs angle measurements using the gyroscope and accelerometer , which are fused using a complementary filter. The heading is also calculated using the magnetometer, without tilt compensation. To view pressure;
This guide covers how to use an Inertial Measurement Unit (IMU) with a Raspberry Pi . This is an updated guide and improves on the old one found here.
I will explain how to get readings from the IMU and convert these raw readings into usable angles. I will also show how to read some of the information in the datasheets for these devices.
This guide focuses on the BerryIMU. However, the theory and principals below can be applied to any digital IMU, just some minor modifications need to be made.
Git repository here The code can be pulled down to your Raspberry Pi with;
When using the IMU to calculate angles, readings from both the gyro and accelerometer are needed which are then combined. This is because using either on their own will result in inaccurate readings. And a special note about yaw.
Gyros – A gyro measures the rate of rotation, which has to be tracked over time to calculate the current angle. This tracking causes the gyro to drift. However, gyros are good at measuring quick sharp movements. Accelerometers – Accelerometers are used to sense both static (e.g. gravity) and dynamic (e.g. sudden starts/stops) acceleration. They don’t need to be tracked like a gyro and can measure the current angle at any given time. Accelerometers however are very noisy and are only useful for tracking angles over a long period of time.
Accelerometers cannot measure yaw. To explain it simply, yaw is when the accelerometer is on a flat level surface and it is rotated clockwise or anticlockwise. As the Z-Axis readings will not change, we cannot measure yaw. A gyro and a magnetometer can help you measure yaw. This will be covered in a future guide.
The IMU used for this guide is a BerryIMUv3 which uses a LSM6DSL, that consists of a 3-axis gyroscope plus a 3-axis accelerometer and a LIS3MDL which is a 3-axis magnetometer.
LSM6DSL – Accelerometer and gyroscope datasheet can be found here.
LIS3MDL – Magnetometer datasheet can be found here
This IMU communicates via the I2C interface.
The image below shows how to connect the BerryIMU to a Raspberry Pi
An accelerometer, gyroscope and magnetometer which is specifically designed for the Raspberry Pi.
What is it?
BerryIMU is an inertial measurement unit, or IMU, that measures and reports on velocity, orientation and gravitational forces, using a combination of an accelerometer, gyroscope and a magnetometer.
IMUs can be found in devices like, quad copters, smart phones, segways, Wii Remote etc.. and are used to sense movement and orientation.
Adding BerryIMU to your Pi will open up a whole new world of possibilities.
BerryIMU is specifically designed for the Raspberry Pi and is designed to take some of the complexity out of IMUs and to try and make them more enjoyable to use. BerryIMU includes the latest and greatest sensor ICs.
I have spend the last month creating a new version of PiBBOT (PiBalancing roBOT) , PiBBOT V2.
This version has a sturdier frame and a LCD display. I replaced the 1.8″ TFT with a LCD as the TFT was causing delays in the main loop timing. I also added a very slim battery for the Raspberry Pi.
A lot of people have asked how I got the readings from the Gyro, Accelerometer, and Compass inertial measurement unit(IMU) which is used to keep PiBBOT upright.
UPDATEDAnd updated guide has been published here, with cleaner and simpler code.
In this guide I will explain how to get readings from the IMU and convert these raw readings into usable angles. I will also show how to read some of the information in the datasheets for these devices. The theory and principals below can be applied to any digital IMU, just some minor modifications need to be made. Eg register values, sensitivity level…
When using the IMU to calculate angles, readings from both the gyro and accelerometer are needed, which are then combined. This is because using either on their own will result in inaccurate readings.
Here is why; Gyros – A gyro measures the rate of rotation, which has to be tracked over time to calculate the current angle. This tracking causes the gyro to drift. However, gyros are good at measuring quick sharp movements. Accelerometers – Accelerometers are used to sense both static (e.g. gravity) and dynamic (e.g. sudden starts/stops) acceleration. They don’t need to be tracked like a gyro and can measure the current angle at any given time. Accelerometers however are very noisy and are only useful for tracking angles over a long period of time.
