Nanopb - Protocol Buffers for Embedded Systems

Nanopb is a small code-size Protocol Buffers implementation in ansi C. It is especially suitable for use in microcontrollers, but fits any memory restricted system.

• Homepage: https://jpa.kapsi.fi/nanopb/
• Documentation: https://jpa.kapsi.fi/nanopb/docs/
• Downloads: https://jpa.kapsi.fi/nanopb/download/
• Forum: https://groups.google.com/forum/#!forum/nanopb

Using the nanopb library

To use the nanopb library, you need to do two things:

1. Compile your .proto files for nanopb, using protoc.
2. Include pb_encode.c, pb_decode.c and pb_common.c in your project.

The easiest way to get started is to study the project in "examples/simple". It contains a Makefile, which should work directly under most Linux systems. However, for any other kind of build system, see the manual steps in README.txt in that folder.

Using the Protocol Buffers compiler (protoc)

The nanopb generator is implemented as a plugin for the Google's own protoc compiler. This has the advantage that there is no need to reimplement the basic parsing of .proto files. However, it does mean that you need the Google's protobuf library in order to run the generator.

If you have downloaded a binary package for nanopb (either Windows, Linux or Mac OS X version), the protoc binary is included in the 'generator-bin' folder. In this case, you are ready to go. Simply run this command:

generator-bin/protoc --nanopb_out=. myprotocol.proto

However, if you are using a git checkout or a plain source distribution, you need to provide your own version of protoc and the Google's protobuf library. On Linux, the necessary packages are protobuf-compiler and python-protobuf. On Windows, you can either build Google's protobuf library from source (see section below) or use one of the binary distributions of it. In either case, if you use a separate protoc, you need to manually give the path to the nanopb generator to the protoc-gen-nanopb plugin, as follows:

protoc --plugin=protoc-gen-nanopb=nanopb/generator/protoc-gen-nanopb --nanopb_out=. myprotocol.proto

Note that the above protoc-based commands are the 1-command versions of a 2-command process, as described in the "Nanopb: Basic concepts" document under the section "Compiling .proto files for nanopb". Here is the 2-command process:

protoc -omyprotocol.pb myprotocol.proto
python nanopb/generator/nanopb_generator.py myprotocol.pb

Building Google's protobuf library from source

When building Google's protobuf library from source, be sure to follow both the C++ installation instructions and the Python installation instructions, as both are required:

1. Protobuf's C++ build & installation instructions
2. Protobuf's Python build & installation instructions

• See additional reading here and here.

Running the tests

If you want to perform further development of the nanopb core, or to verify its functionality using your compiler and platform, you'll want to run the test suite. The build rules for the test suite are implemented using Scons, so you need to have that installed (ex: sudo apt install scons on Ubuntu). To run the tests:

cd tests
scons

This will show the progress of various test cases. If the output does not end in an error, the test cases were successful.

Note: Mac OS X by default aliases 'clang' as 'gcc', while not actually supporting the same command line options as gcc does. To run tests on Mac OS X, use: "scons CC=clang CXX=clang". Same way can be used to run tests with different compilers on any platform.

Build systems and integration

Nanopb C code itself is designed to be portable and easy to build on any platform. Often the bigger hurdle is running the generator which takes in the .proto files and outputs .pb.c definitions.

There exist build rules for several systems:

• Makefiles: extra/nanopb.mk, see examples/simple
• CMake: extra/FindNanopb.cmake, see examples/cmake
• SCons: tests/site_scons (generator only)
• Bazel: BUILD in source root
• PlatformIO: https://platformio.org/lib/show/431/Nanopb

And also integration to platform interfaces:

• Arduino: http://platformio.org/lib/show/1385/nanopb-arduino