nanopb exploration

• This repository is a sandbox for exploring nanopb's functionalities and getting a better grasp on how it works.
• The exploration happens through the implementation of a handful of very verbose examples
• Each Example is a slightly more complex usecase then the previous one.
  • Even if your use case is simple, it's recommended to check the later examples for they might use more elegant and better fitting approaches for your usecase.
• All examples, when executed, generate binary files whose content represent the protobuf payload.
  • These files can be used with protoc --decode option to debug as is explained in section Usage and troubleshooting

Examples:

• ExampleA: Simplest example;
• ExampleB: Streams custom callbacks;
• ExampleC: Fields callbacks for repeated fields;
• ExampleD: Fields callbacks for repeated fields + repeated sub messages;
• ExampleE: Protocol.options file + usage of fixed size char field;
• ExampleF: Use HDLC protocol to control message framing where the message payload is protobuf encoded;

This project uses:

• cmake & make are used as build system
  • cmake version 3.22.1
  • GNU Make 4.3
• clang-format is used as formatter/code beautifier
  • Ubuntu clang-format version 14.0.0-1ubuntu1
• yahdlc is used as HDLC protocol library (already contained in the 'external' folder)
  • 1.1
• nanopb is used as a C implementation of Google's protobuf (already contained in the 'external' folder)
  • nanopb-0.4.5
• An NXP ring_buffer implementation is also imported into the workspace (already contained in the 'external' folder)

How to compile and run the examples

• If you wish to use docker, build the image and launch it using the helper scripts inside of the docker folder
• The repository can be operated outside of the docker container if all the dependencies are met
• To format the complete code base with clang-format:

./bbuild.sh -f

• To build the exampleA:

./bbuild.sh -b exampleA

• To rebuild the exampleA:

./bbuild.sh -r exampleA

• To execute the built binary of the exampleA:

./bbuild.sh -e exampleA

• To format, build and execute the exampleA:

./bbuild.sh -f -b -e exampleA

• Examples:

./bbuild.sh -v -f -b -e exampleA # To format, build and execute the exampleA with verbose

• To check all options available:

./bbuild.sh --help

Dealing with nanopb and protobuf

Installation

• Installs nanopb generator script and protoc

sudo apt-get update
sudo apt-get install nanopb
which protoc
which nanopb_generator.py 

Usage and troubleshooting

• protoc usage:

protoc --python_out=. protocol.proto
protoc --decode Sample exampleC/protocol.proto < protobuf_payload.bin

• nanopb usage:

nanopb_generator.py protocol.proto

• Helper tool to debug protobufs:
  • https://protobuf-decoder.netlify.app/