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.
- A lot more comments.
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):
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 )
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.
Source: lucadentella.it – Arduino, delay() vs millis()
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!
CAVA was created by Karl Stavestrand and it is a great tool to create an audio visualizer in the console.
Continue reading Raspberry Pi 3 + LED Cube + Spectrum Analyzer = Awesome Audio Visualizer!
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
Continue reading How to Program an AVR/Arduino using the Raspberry Pi GPIO
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
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.
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!
Source: Super low cost VGA output for the Pi Zero • Hackaday.io