This was an experiment with nix/c++ and opencv. I wanted to see if nix could be a useful solution for big projects on embedded systems. Nix has support for some popular embbeded boards, so I thought it was worth pursuing.
- Add multithread support for camera streams.
- Working camera stream.
- Display image segmentation masks from pytorch models.
- Optimize the ML segmentation camera stream for realtime speeds.
- Improve segmentation accuracy. (Current masks are not useable for navigation)
- Modularize codebase to allow seperation of tasks amongst threads and classes.
The libraries are added via nix packages housed inside the libraries folder. The libraries folder current has three libraries residing in it. Pytorch and httplib, while spdlog is included it is not integrated with the main flake.nix file. (Due to some compile errors) The reasoning behind using nix for dependencies instead of the countless other package managers for c++ or any other language. Is reliability and cross-compliation, by building the source code for each library we can avoid the massive headache of sourcing binanaries and dependencies for libraries when deploying to arm based systems.
First, because nix is awesome you don't need to download anything (except for nix). After cloning the repo make sure you have nix flakes enabled. Make sure that a camera is on /dev/video0 then execute this command ./build-run.sh it will take some time. But when its finished the camera server will be running on http://localhost:8080/stream!
There are three main nix commands that you will need to know to develop with nix. It's the build and develop commands prefixed with nix like so: nix develop or nix run. Now for the next question what do all three really do?
It will compile the project according to the nix configuration files like flake.nix or and other .nix file. CMake is used for building the raw executable, but nix manages the steps and environment that cmake receives to build the binaries in. When its completed a new folder named result will be available with the compiled binary ready.
Cannot use nix run because the ros libraries are not packaged into the binary. This means you need to build the program and then execute it in the shell provided by nix develop. There is a script to make this easier called build-run.sh
It will compile the devshell which is a custom development environment with all the libraries and headers necessary to develop this project. Its nice when executed you have a full fledged dev environment without any configuration necessary as a new developer.
I decided to use valgrind for memory debugging since its reliable and its been around for awhile. Use the command below to execute teleop-control with valgrind. Make sure you run nix build before using valgrind since it doesn't compile the binary by itself.
valgrind --leak-check=yes ./result/bin/teleop-controlWrite something saying how wsl is not plug and play for this project and that native linux is much easier to configure.