Better Engine Control Software

ECS but better

This is a redesign of the current Engine Control System. In addition to the before aims of safety and reliability, this redesign focuses on better readability through object-oriented design.

Currently, we are using a RaspberryPi based electronics system to control the test stand. On the actual rocket, we will be using a custom PCB.

Pulling ECS Repository

From here, your first step should be to clone the most recent version of the Engine Control Software (ECS):

git clone --recurse-submodules https://gitlab.com/aeronu/dollar-per-foot/better-engine-control-software.git

if you forgot the --recurse-submodules flag (aka a regular git clone), you need to run

git submodule init
git submodule sync
git submodule update

as well.

The current working code should be in the main branch

General System Design

TODO: Add picture of the wiring system we have here

----------- IGNORE THIS SECTION FOR NOW IF YOU ARE NOT SETTING UP A PI FROM SCRATCH-----------

Getting Started with RaspberryPi

To get started you'll first need a Pi, a 5V, a 2-2.5A power supply, a micro-sd card (if not already in the pi), and an ethernet cable.

Flashing the OS

If the Pi has not been set up yet, you will need to flash the OS to the microSD card. We are currently using the default version of the RaspberryPi OS Lite (without Desktop).

Connecting to the Pi

Once the operating system has been flashed, the easiest way to connect to the Pi will be over ssh. Connect your laptop to the Pi via ethernet and run ssh [email protected]. The default password for any new Pi OS is raspberry.

If you are not cross-compiling, you will need to do the below as well

Pulling ECS Repository

From here, your first step should be to clone the most recent version of the Engine Control Software (ECS): git clone https://gitlab.com/aeronu/dollar-per-foot/better-engine-control-software.git. From here, switch to the appropriate branch (or use main if you're just testing the simulator).

Dependencies

Before building you'll need to install CMake: sudo apt-get install cmake. CMake is the build system we use for all of our C++ code. While it is generally bundled as part of certain operating systems or as part of IDEs, it is not installed by default on the Pi.

Before moving on you should check the version of cmake with cmake --version. If you have less than 3.16, run sudo apt-get update and then sudo apt-get upgrade to update your packages.

----------- END IGNORE -----------

Building ECS

Dependencies

To build this repo, you will need a C++ and C compiler, and CMake

Linux/Unix systems

Typically these systems will include a C++ and C compiler out of the box, usually GCC. However, it might be out of date because we are using C++20, one of the newest versions. Chances are CMake isn't included either.

To install, download using your distro's package manager. For Debian/Ubuntu this should be apt-get.

For example you will probably type

sudo apt-get install [WHATEVER THE NEWEST GCC COMPILER PACKAGE IS]
sudo apt-get install cmake

into the command line on a Debian/Ubuntu system

Mac systems

TODO: Apple's C++ compiler, AppleClang is really slow to implement new features. We have to install a newer one

Windows systems

The easiest way to build on Windows is probably to use Microsoft Visual C (MSVC), which comes with Visual Studio. It's really big but the only way I've found to make it actually work on Windows. CLion deals with all the cmake/make stuff for you, and allows for debugging.

• Download Visual Studio Commuinty, and run it
• Click 'Continue'
• We'll just want 'Desktop development with C++'.

Actually building

Through the command line/terminal

Now that you have the dependencies installed

• navigate to the ECS repository you cloned in the command line
• run the following command

cmake -S . -B build

This process will create a build directory that will house all of the build files and keep the clutter out of the source repository. CMake is responsible for creating the Makefile/Ninjafiles that will build the code.

There are three executables that can be built and used: ecs_sim, ecs_pi, and ecs_quick.

1. ecs_sim is an entirely simulated version of the control system. The simulator can be configured by modifying the simulator config (planned feature).
2. ecs_pi is the executable used to actively control relays and read sensors from the stand. Because of its dependencies it is likely impossible to build local, but should build fine on the pi. This is the executable that should be used on the test stand.
3. ecs_quick is if you want to quickly build and try a test script, just don't forget to tweak the CMake file!

NOT CURRENTLY IN THE REDESIGN: ecs_hybrid is a mix of ecs_sim and ecs_pi. It runs two versions of the control software simultaneously and is used for actively controlling the stand while providing synthetic data from the simulation. This is ideal for training scenarios as it can be treated as a real test where the operator is actuating valves and reading real-looking values. Because this executable has the same dependencies as ecs_pi it will not be able to be built locally.

• If we see a need for it, we can add it

Once you have determined which executable you would like the build, you can run the command

cmake --build build -t [EXECUTABLE NAME]

where [EXECUTABLE NAME] is replaced with the appropriate executable name.

some highlights you will probably be running are

cmake --build build -t ecs_sim # our simulated ecs binary
cmake --build build -t all_tests # our test suite

If you would like to build all executables at once (again, only possible on the pi itself and will take some time), you can just run

cmake --build build

All executables will be placed inside the build/ directory. Inside the build directory you should be able to find your [executable name] executable, it might be buried in some folders though.

Through an IDE

If you don't want to build through the cmdline, you can use your IDE.

I don't have a runthrough for VSCode, but it should be easy enough to search up

Here are some directions for CLion:

We can now import our project into CLion. In CLion, go to "Open" -> "better-engine-control-software/CMakeLists.txt" -> "Ok" -> "Open as Project"

In the Open Project Wizard, add our MSVC "toolchain" with "Manage toolchains" -> + sign -> Visual Studio. Click OK and OK

Navigate to src/main_sim.cpp, click the green arrow next to int main() and click Run.

Cross compiling for Pi using Docker

Cross-compiling is when you build a program on one kind of computer, but make it run on another. In our case, we can cross compile for Raspbian (the Pi os) from Ubuntu pretty easily.

We use docker for this, because I found a Docker image (sorta like a VM) for Ubuntu that has everything set up for us already. However, note that you can't actually run the executable on your computer, even in the Docker container. That's because Docker isn't really a fully fledged virtual machine. For example, if your computer's architecture differs (RPi is ARM, if your computer is x86 for instance), Docker doesn't abstract over than, your binary will fail to run.

Here's the steps to cross-compile the ecs_pi executable, which you run from the root directory of this project:

You may need to follow these Docker install instructions if sudo apt install docker.io doesn't work. Then, add yourself to the docker group:

# Probably unneeded, it makes one automatically
sudo groupadd docker
sudo usermod -aG docker $USER
# Run this, or log out and then in, to register changes
newgrp docker 

To actually build, use ./cross_compile_ecs_pi_debug.sh or ./cross_compile_ecs_pi_release.sh. The debug variation will spit out more helpful data in case of a crash, the release variation will be more efficient

How it works (from Matt): I copied a bunch of toolchain file stuff from wpilib (thanks wpilib!). The script above starts a docker container, creates the cmake makefile stuff with cmake -B build-pi -DCMAKE_BUILD_TYPE=Release -DCMAKE_TOOLCHAIN_FILE=CMake/arm-pi-gnueabihf.toolchain.cmake, and then builds it.

To then copy to the Pi, run ./install_docker.sh. For convienence, you can install your SSH key onto the Pi:

• If you don't yet have a id_rsa.pub in ~/.ssh, create it with ssh-keygen
• Install with ssh-copy-id [email protected]

Connecting a GUI to the ECS

If running the ECS locally, connect the GUI to localhost:9002

If running the ECS on the pi with a laptop connected via ethernet, connect the GUI to raspberrypi.local:9002

Get up to speed

This project uses C++ for implementation, CMake for building, and Catch2 for unit-testing. Below are some tutorial links if you want to get a idea of how these tools work.

C++

C++ is a FAMOUSLY hard language to learn. And unfortunately, most of the online tutorials are DOGSHIT. I'll probably run through some basic C++ classes during some meetings. But I've also started a folder of references/tutorials in the c++_tutorial_markdowns folder, take a look!

Catch2:

• Note: We are not using the latest version of Catch2. Newer versions have abandoned the single-header include. As we do not currently need sophisticated features for our tests, we use the older single header-file due to its convenience
• A pretty in-depth tutorial
• The official quick tutorial
  • just ignore the "Getting Catch2" section because we are using the old versions

CMake:

• A tutorial that goes over common terms and functions
• A tutorial that goes a bit more in depth, this is the one you want to study if you actually want to know CMake
• Another one