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Building and Running the Pinball Autopilot on the Raspberry Pi

The source code lies and building happens inside the folder called pinballProject. For a fresh build, you need a not too old version of make, a C++ compiler (we only tested g++), an internet connection (for downloading the Kieler Compiler), the libraries wiringPi and opencv as well as the command-line tools mega-cmd and python2. The tool for (and also python2) can be omitted (see below on how to compile without them), everything else except for opencv comes pre-installed with Raspbian. For opencv you need a 4.x version, 4.2.0 ought to work for example. Make sure to enable the option that the entries for pkg-config get configured. It can be built from source on the Raspberry Pi in a few hours, make sure not to use too many threads for compilation because of limited RAM, also perhaps increase the swap.

With all the prerequisites met, you can use the Makefile to build everything.

CommandFunctionality (All the builds are incremental, i.e. only happen once when the source code is unchanged.)
makesame as make build_all
make build_allBuild the main executable as well as the tools video_capture and calibrate.
make buildBuild the main executable “main”.
make runBuild and execute the main executable.
make ...xyzMake file called “”, if a recipe exists. Most notably for ...xyzcalibrate
make capture

Build video_capture and execute it. This tool can only be executed on the Pi and can record a video
during manual gameplay which is then uploaded to with a new numerical file-name.

make get

Executes a python script that can (interactively) get a recorded video from the folder.
Intended for getting video input files transferred to a different machine (not the Pi) for testing the image detection.

make cleanRemoves all generated files except for _pi_logged_in, downloaded videos and the downloaded Kieler Compiler.
make clean_allLike make clean, but without the exceptions. This will delete everything in the folder video!

For instructions on how to use the ./calibrate, see World Coordinate System.

Working without (and python): On the pi, you need to create a file called _pi_logged_in (e.g. with touch _pi_logged_in) before calling make for the first time. On a different machine, you don’t need to do this. You cannot use make capture or make get without these command-line tools.

If future updates of mega-cmd or the command-line Kieler Compiler kico.jar include relevant breaking changes, you might need to resolve those problems (work without mega-cmd or acquire a kico.jar from around March 2020).

Setting up the Pi for Better Real Time Performance

The program will stick its latency-sensitive threads for controlling the IO pins and for image processing to the cores 3 and 4 of the 4-core Raspberry Pi. To ensure best real-time performance, please configure the kernel parameter isolcpus=2,3 (they count starting from 0) to the file /boot/cmdline.txt and reboot. This will make sure that the operating system doesn’t schedule any other tasks on those cores.

Building and Running on Any Other Linux Machine

The program can be built and partially run on other machines. There you potentially need to install all the requirements yourself. However, wiringPi is not needed. Also don’t use a machine where the current user is called pi, since that would confuse the compilation flags. We’ve observed problems with a too old version for make, without knowing the exact lower bound, 4.2.1 is definitely new enough. Possibly python2 needs to be installed on your machine. Compared to a Raspberry Pi, compilation of opencv on your machine is going to be a lot more fun (way faster and no issues with too little RAM). Regarding versions, see the relevant section above; note that pkg-config is needed, too, in case you don’t have that installed already.

Running the make commands works like on the Pi. Just make capture is not available. The main program will behave differently. It will prompt you for the name (without extension) of a video file in the video folder. Make sure to get some file in there; at the time of writing this, there is a file called 1 in the that you can get via make get, as well as a few more named video files that were created before we had the make capture command.

After choosing a video file, the program starts using the video input in “real time”; however, since things are not really real-time, the logic controller part does not work too well. (Simulating the flow of time properly is not fundamentally a problem but something we didn’t finish implementing.) This means you should mostly ignore the debug-printouts about ticks happening. What you can really test is the image processing / ball detection. This works better than on the Pi, because we are providing controls for pausing or changing the playback speed. Press a key while any of the windows opened by the main program is in focus.

KeyPlayback effect
+increase playback speed ×2
-decrease playback speed ×0.5
.while paused, advance by one frame

If you recalibrate the coordinate system on the Pi, you might want to transfer the config file for the coordinate system (however there is nothing really depending on the coordinate transformation being correct inside the image detection anyways).

The ability to compiler the whole project off the Pi allows for catching type errors etc. more quickly, since compilation on the Pi tends to be a lot slower and also there‘s not the option to use the Kieler IDE on it (so you’d maybe also need to transfer the code). The pinballProject folder contains an Eclipse project that can be used with Kieler. Building from the Kieler IDE still happens by invoking the Makefile. There should be a build configuration using make included in the project. (I’m only specifying “should” since we didn’t really test the experience of importing the project into a workspace too often.)

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