The EFIS of the Cesna Citation X consists in 2 PDF, 2 ND and 1 EICAS. All 4 screens have the same dimensions, appox. 160x190 cm (WxH in vertical orientation) according to my measurement on the cockpit drawings extracted from the 3D model (read more in [[the mechanical section|Mechanical-design]]).
Is is possible to get the real ratio by looking at the property tree (/canvas/by-id/canvas[X]) : 900x1024 px i.e.1:1.14.
There a plenty of small LCD screens on ebay. They cost approx. 20€ and have a display area that measures 86x154 mm. As the width is limited to 86 mm, the canvas will be 86x98 mm, only using 2/3 of the screen area.
In conclusion, if I use these 7-inch LCD, the canvas will be (ridiculously) small and use only 2/3 of the screen. For me, it does not worth spending 100 € for that result.
On this picture, the PFD are full-size because displayed by a computer screen, and the EICAS is smaller because rendered on a 7-inch LCD screen. ND displayed are not shown
The second solution is to use two computer screens bought at my local dump shop. With their size, each can cover a PFD and a ND. For the EICAS in the middle, I will temporally opt for the 7-inch screen.
James Turner alias zakalawe has developed a a standalone Qt program within the flightgear repository, that renders canvas. This program can be run on a separate computer, as long as it can connect to the computer running flightgear.
I have subtreed FGQCanvas here.
When I started my project, the latest available version of Raspbian was Stretch. Unfortunately, this version only shipped Qt 5.7 while FGQCanvas requires Qt 5.9 minimum since it calls QWindow.setFlag. I tried to cross-compile Qt 5.9, as James Turner did, following these instructions but I did not succeded.
I waited July 2019 and the release of Raspbian Buster, shipping Qt 5.11.3. Here is what I did:
- Download the Raspbian Buster with desktop image from Raspbian webpage.
- Copy the image using
sudo dd bs=1M if=2019-07-10-raspbian-buster.img of=/dev/sde conv=fsync
beware that I have used a 1Mb block, 4M did not work for me, the card was not booting - Copy my private ssh keys in order to be able to clone my subtree of the fgqcanvas util of flightgear
git clone git@github.com:adessein/fgqcanvas.git - In order to be able to compile I had to install the following packages
sudo apt-get install qt5-default qtdeclarative5-dev libqt5websockets5-dev qtdeclarative5-private-dev qtbase5-private-dev - And then
qmake fgcanvas.pro && make
The mockup/configurations are saved as JSON files in the folder ~/.local/share/FlightGear/FGCanvas
Start the application using ./fgqcanvas your_config.json