Is there support for Google's Common Types (e.g. timestamp.proto) for nanopb in Zephyr?

[Aaron F]

I am wondering about the common types defined by google and available as part of the standard protoc compiler. I would like to use the Timestamp and Duration types. I have added the following line to my .proto file.

import "google/protobuf/timestamp.proto";

Running protoc from the command line handles this just fine, even though there is no "timestamp.proto" in the project. Running the build for the nRF5340 from VS Code however fails with the message "fatal error: google/protobuf/timestamp.pb.h: No such file or directory".

The CMakeLists.txt is set up the same as in zephyr/samples/modules/nanopb.

find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})

project(NONE)

#NANOPB

# Note that here, we're adding CMAKE_SOURCE_DIR to the include path for nanopb.

# This is needed because the below call to nanopb_generate_cpp() is using

# 'RELPATH .'

set(NANOPB_OPTIONS "-I${CMAKE_SOURCE_DIR}")

nanopb_generate_cpp(proto_sources proto_headers RELPATH .

    src/interface.proto

)

Is this simply not possible, or do I need to do something different with the CMake?

[Naeem Maroof]

Hello Aaron,

I will look into this and will come back once I have more information.

Regards, Naeem

[Naeem Maroof]

Hi Aaron,

I was able to see the same issue as you have described, and I was not able to resolve it.

Maybe you can ask at Zephyr discord group.

[Aaron F]

Hi Naeem,

I had a thought about this. With protobuf, you have to explicitly list each file you want compiled. That includes things like the Google Common Types. I realized when compiling the same files for Python using the protoc compiler that it got the same error and that google/protobuf/timestamp.proto has to be compiled explicitly. It's the same with nanopb.

In this case nanopb is working fine, but the build fails in compilation because the compiled form of timestamp.proto doesn't exist.

I'm not sure how to give nanopb the path to the built-in common types. Perhaps it's just google/protobuf/timestamp.proto? I've already worked around this by copy-pasting the desired message definitions into the project's proto file.

However it's done, it's probably through the nanopb_generate_cpp() function. The only documentation I could find for it is in the source code here.