Generating code

Introduction

Generating code may be straightforward but involves downloading software, updating your compiler, and getting the command just write for your language. To ease this pain:

• CLI scripts are pushed to the Protobuf repository with the exact command for each language

• Generated code is pushed to shared repositories (by language)

Together, this means that only a handful of people need to be educated on how to generate code, and they can push it for others to use without requiring everyone to download Protobuf.

Getting set up

You can find the Protobuf compiler (protoc) here. The compiler only supports a few languages by default and needs special setup for some languages

Dart

To setup your Dart installation, install the protoc-plugin package to your computer:

dart pub global activate protoc_plugin

The compiled code will import the protobuf package, which you need to add to each project:

dart pub add protobuf

Nanopb (C++)

The protoc compiler has C++ support out-of-the-box, but it's not fit for microcontrollers like Arduino. Instead, we use another toolchain called nanopb, which both provides the compiler and the libraries that it will import. The libraries are already included in the Firmware-Utilities repository, but you'll need to install the Python-based compiler yourself:

pip install nanopb

Nanopb has many differences compared to the standard Protobuf, especially when comparing C++ to more modern languages, but so long as you follow the Guidelines, the code should be compatible.

Compiling code

Recall that we push our code to a shared repository for each language (Generated code). For the firmware, we need to generate code in each repository as well.

Git Submodule

We first need to include the Protobuf code in each repository so we can compile it. Instead of cloning the Protobuf repository, include it as a submodule, a nested library.

git submodule add https://github.com/BinghamtonRover/Protobuf

A submodule is a whole other repository, so to make changes to Proto files, cd into it, make a new branch and test your changes. When you're ready push and open a PR. Whenever you pull or change commits, you'll need to git add that to the parent repository as well.

Using our build scripts

Once you have the desired compiler in your path, you can use our build scripts in the Protobuf repository to handle the build for you. These scripts are written in a language you'll already have.

Dart

At the root of your Dart project, the following comand compiles all Protobuf files

dart gen_dart.dart

Nanopb (C++)

In a firmware repository, first submodule the Proto files as explained above, then run:

python generate_arduino.py -s SKETCH_NAME -p PROTO_NAME

Unlike Dart, Arduino will compile all available source code. To avoid compiling code we do not need, use this command with just the name of the Protobuf file you need. core.proto is already compiled in firmware-utilities.

More resources

• The Protobuf Dart tutorial

• The Nanopb docs

• The Protobuf Wire Format