# BerryIMU Python Code Update - Kalman Filter and More

We have updated to the python code in our git repo.

It now includes;

• The elusive Kalman filter.
• Math needed when the IMU is upside down
• Automatically calculate loop period.

What is a Kalman filter?  In a nutshell;
A Kalman filter is, it is an algorithm which uses a series of measurements observed over time, in this context an accelerometer and a gyroscope. These measurements will contain noise that will contribute to the error of the measurement. The Kalman filter will then try to estimate the state of the system, based on the current and previous states, that tend to be more precise that than the measurements alone.

A Kalman filter is more precise than a Complementary filter. This can be seen in the image below, which is the output of a complementary filter (CFangleX) and a Kalman filter (kalmanX) from the X axis plotted in a graph.

The red line (KalmanX) is better at filtering out noisep;

The code can be found here in our Git repository here
And  can be pulled down to your Raspberry Pi with;

pi@raspberrypi ~ \$ git clone https://github.com/mwilliams03/BerryIMU.git

A summary of the code;

def kalmanFilterY ( accAngle, gyroRate, DT):
y=0.0
S=0.0

global KFangleY
global Q_angle
global Q_gyro
global y_bias
global XP_00
global XP_01
global XP_10
global XP_11
global YP_00
global YP_01
global YP_10
global YP_11

KFangleY = KFangleY + DT * (gyroRate - y_bias)

YP_00 = YP_00 + ( - DT * (YP_10 + YP_01) + Q_angle * DT )
YP_01 = YP_01 + ( - DT * YP_11 )
YP_10 = YP_10 + ( - DT * YP_11 )
YP_11 = YP_11 + ( + Q_gyro * DT )

y = accAngle - KFangleY
S = YP_00 + R_angle
K_0 = YP_00 / S
K_1 = YP_10 / S

KFangleY = KFangleY + ( K_0 * y )
y_bias = y_bias + ( K_1 * y )

YP_00 = YP_00 - ( K_0 * YP_00 )
YP_01 = YP_01 - ( K_0 * YP_01 )
YP_10 = YP_10 - ( K_1 * YP_00 )
YP_11 = YP_11 - ( K_1 * YP_01 )

return KFangleY

# Arduino -The Difference between delay() vs millis()

Luca has written up a great tutorial on the differences between delay() and millis() on the Arduino, which i think is worthwhile to share.   He also presents it in a very easy to understand format.

# Raspberry Pi 3 + LED Cube + Spectrum Analyzer = Awesome Audio Visualizer!

To create an awesome audio visualizer, using a spectrum analyzer( C.A.V.A:  Console-based Audio Visualizer for ALSA ), all you need is a Raspberry Pi 3 and a RGB LED cube - VoxCube!

# C.A.V.A

CAVA was created by Karl Stavestrand and it is a  great tool to create an audio visualizer in the console.

# How to Program an AVR/Arduino using the Raspberry Pi GPIO

In this tutorial I am going to show you how to program an AVR(ATmega328) and an Arduino UNO using the GPIO on the Raspberry Pi.

Adding an Arduino or an AVR to your projects will give you much greater flexibility.

# Hook up the Raspberry Pi to the Arduino UNO or AVR.

The image below shows how to connect a Raspberry Pi 2 and an  Arduino UNO. click the image to make it larger

# Raspberry Pi controlling a LED cube with Python

The above LED cube [VoxCube] is being controlled via a Raspberry Pi, using python and the official Raspberry Pi display.

Buttons were setup using the Kivy. Kivy is a Python library which makes creating buttons and events with a touchscreen very easy.

Here is a very good guide on how to get Kivy setup on a Raspberry Pi.
Continue reading Raspberry Pi controlling a LED cube with Python

# New Kickstarter - VoxCube - 8x8x8 RGB LED Cube for the Raspberry Pi

We have been busy over the last 6 months creating something special!
We have always liked the idea of LED cubes, however there was no easy way to drive these LED cubes with a Raspberry Pi.... until now.

VoxCube is an 8x8x8 RGB LED Cube which has been specifically designed for the Raspberry Pi, however it is also compatible with other microcontrollers. E.g. Arduino

Cubes can also be chained together, the image below is four VoxCubes being controller via a Raspberry Pi.

Head over to the Kickstarter page for more details.

# Super low cost VGA output for the Pi Zero • Hackaday.io

Here is a great post by mincepi which shows how to enable VGA output on a Pi Zero for less than \$5

The vga666 by Gert is already a low cost VGA output option for the Pi. But we can do better with the Zero! We'll use 16 bit output instead of 18 bit: this frees up the SPI and I2C ports with little loss in quality. The resistors can be soldered between the Zero and the adapter, making the PCB smaller and eliminating a connector. I've determined that 5% resistors are good enough: no need for higher cost 1% units. By not using the middle row of pins in the HD15 connector, we can straddle-mount it on the PCB edge. Finally, the connector can be male, so the Zero will connect to the monitor ChromeCast style: no VGA cable needed. (This connector could even be scrounged from an old VGA monitor cable for free!) If you order the boards from OSHPark, it will cost \$4.95 for three copies. Enough resistors and connectors to build three will cost \$5.92 from Digi-Key. That works out to \$10.87 to build three, or \$3.62 each!

# Self Driving RC Car with a Raspberry Pi and Arduino

Here is a great project by Zheng Wang, which uses a Raspberry Pi and an Arduino to create a self driving car.

"Objective Modify a RC car to handle three tasks: self-driving on the track, stop sign and traffic light detection, and front collision avoidance."

# BerryIMU and Pi Zero

BerryIMU is a perfect companion for Pi Zero.

We have confirmed that BerryIMU is 100% compatible with the Pi Zero. BerryIMU can sit right on top of Pi Zero header pins while still maintaining a very low profile.

# BerryIMU code for Arduino - Accelerometer, Gyroscope and Magnetometer

Our GIT repository has been updated with an Arduino sketch which calculates angles using a complementary filter.  The heading is also calculated using the magnetometer.

## Detailed Guides and Tutorials

These cover both BerryIMU and displaying graphics with SDL on a Raspberry Pi;
How to Create an Inclinometer using a Raspberry Pi and an IMU