This directory contains the applications for embedded Linux systems such as the Raspberry Pi and Intel Edison. This description assumes that the Edison image was built using the meta-edison-rt layer, available on the GitHub repo.
The RTIMULibvrpm demo app, which shows how to integrate RTIMULib with vrpn, has its own build and run instructions in a README.md within the RTIMULibvrpn directory.
The easiest way to connect the IMU to the Raspberry Pi is to use something like the Adafruit Pi Plate (http://www.adafruit.com/products/801) as it makes it obvious where the I2C bus 1 pins are and where to pick up 3.3V. Basically, you need to connect the I2C SDA, I2C SCL, 3.3V and GND to the IMU breakout board you are using. Take care with these connections or else disaster may follow!
Add the following two lines to /etc/modules:
i2c-bcm2708
i2c-dev
Then, comment out the following line in /etc/modprobe.d/raspi-blacklist.conf:
# blacklist i2c-bcm2708
Restart the Raspberry Pi and /dev/i2c-0 and /dev/i2c-1 should appear. It’s also useful to install the I2C tools:
sudo apt-get install i2c-tools
Then:
sudo i2cdetect -y 1
will detect any devices on /dev/i2c-1. If you have the MPU9150 wired up, you should see it at address 0x68. This is the default address expected by the demo programs. If it is at 0x69, the address expected by the demo programs will need to be changed (there's a settings file for doing things like that so it's easy to do).
By default, the I2C devices are owned by root. To fix this, reate a file /etc/udev/rules.d/90-i2c.rules and add the line:
KERNEL=="i2c-[0-7]",MODE="0666"
The Raspberry Pi will need to be rebooted to implement this change.
Another thing worth doing is to change the I2C bus speed to 400KHz. Add the following line to /boot/config.txt:
dtparam=i2c1_baudrate=400000
Simplest thing is then to reboot to make this change.
The I2C bus should now be ready for operation.
The Raspberry Pi requires that cmake is installed. Enter:
sudo apt-get install cmake
If the Qt-based GUI programs are to be compiled, also install Qt:
sudo apt-get install libqt4-dev
It's necessary to add an extra directory to ldconfig. Create /etc/ld.so.conf and add the line:
/usr/local/lib
Then run ldconfig so that the RTIMULib libraries will be found.
Go to the directory where RTIMULib was cloned and enter:
mkdir build
cd build
cmake ..
make -j4
sudo make install
sudo ldconfig
This will build and install all of the libraries and demo programs. Note that the Intel Edison does not need the "sudo" since the default user is root. The "-j4" part indicates how many cores should be used and will considerably speed up the build on the Pi2 and Edison.
Makefiles are provided for RTIMULibCal, RTIMULibDrive, RTIMULibDrive10 and RTIMULibDrive11. To build, navigate to the directory for the app and enter:
make -j4
sudo make install
.pro files are included for RTIMULibDemo and RTIMULibDemoGL. To build using qmake, navigate to the RTIMULibDemo or RTIMULibDemoGL directory and enter:
qmake
make -j4
sudo make install
The .pro files can also be used with QtCreator if desired.
RTIMULibCal can either add calibration data to an existing RTIMULib.ini or else create a new one with the calibration data. RTIMULib.ini is used/created in the working directory.
If magnetometer ellipsoid fit isn't required, RTIMULibCal can be run anywhere. If ellipsoid fit is required, then the program assumes that the RTEllipsoidFit directory is at the same level as the working directory so that "../RTEllipsoidFit" refers to the directory holding the RTEllipsoidFit.m octave program. If not, ellipsoid fitting will fail. Note - ellipsoid fit is not supported on the Intel Edison.
The normal process is to run the magnetometer min/max option followed by the magnetometer ellipsoid fit option followed finally by the accelerometer min/max option. The program is self-documenting in that the instructions for every option will be displayed when the option is selected.
The resulting RTIMULib.ini can then be used by any other RTIMULib application.
RTIMULibDrive is a simple command line program that shows how simple it is to use RTIMULib. RTIMULibDrive10 extends this to also support 10-dof IMUs with pressure/temperature sensors. RTIMULibDrive11 adds humidity sensor support to RTIMULibDrive10.
You should be able to run the program just by entering RTIMULibDrive(10/11). It will try to auto detect the connected IMU If all is well, you should see a line showing the sample rate and the current Euler angles. This is updated 10 times per second, regardless of the sensor sample rate. By default, the driver runs at 50 samples per second in most cases. So, you should see the sample rate indicating around 50 samples per second. The sample rate can be changed by editing the .ini file entry for the appropriate IMU type.
The displayed pose shows the roll, pitch and yaw seen by the IMU. Using an aircraft analogy, the roll axis points from the pilot towards the nose, the pitch axis points from the pilot along the right wing and the yaw axis points from the pilot down towards the ground. Right wing down is a positive roll, nose up is a positive pitch and clockwise rotation is a positive yaw.
Various parameters can be changed by editing the RTIMULib.ini file. These are described later.
Take a look at RTIMULibDrive.cpp. Quite a few of the code lines are just to calculate rates and display outputs!
To run the program, the Raspberry Pi needs to be running the desktop. To do this (if it isn't already), enter:
startx
Then open a command window and enter:
RTIMULibDemo
You should see the GUI pop up and, if everything is ok, it will start displaying data from the IMU and the output of the Kalman filter. If the MPU9150 is at the alternate address, you'll need to edit the RTIMULib.ini file that RTIMULibDemo generated and restart the program.
To calibrate the compass, click on the "Calibrate compass" tab. A new dialog will pop up showing the maximum and minimum readings seen from the magnetometers. You need to waggle the IMU around, ensuring that each axis (roll, pitch and yaw) point straight down and also straight up at some point. You need to do this in an area clear of magnetic fields otherwise the results will be distorted. Eventually, the readings will stop changing meaning that the real max and min values have been obtained. Click on "Ok" to save the values to the RTIMULib.ini file. Provided this .ini file is used in future (it just has to be in the current directory when RTIMULibDemo is run), the calibration will not have to be repeated. Now that RTIMULibDemo is using calibrated magnetometers, the yaw should be much more reliable.
The .ini file created by RTIMULibDemo can also be used by RTIMULibDrive - just run RTIMULibDrive in the same directory and it will pick up the compass calibration data.
Running RTIMULibDemoGL is exactly the same except that it takes place in the RTIMULibDemoGL directory.