esp-idf-protocol-buffer

Example of Google Protocol Buffers Serialize and Deserialize with ESP-IDF.

In MQTT for IoT devices, JSON is used as the serialization format of the message.
However, for low-performance hardware, JSON parsing in C is a heavy load.
So when I was looking for a good serialized format that could be implemented in C, I found protobuf.

ESP-IDF includes this Google Protocol Buffers library.
You can use Protocol Buffers components as standard.
But there is no example code in ESP-IDF.

I ported from this.

Software requirements

esp-idf v4.4/v5.x.

Installation

git clone https://github.com/nopnop2002/esp-idf-protocol-buffer
cd esp-idf-protocol-buffer
idf.py flash monitor

• Serialize

I (328) MAIN: Writing 4 serialized bytes
I (338) MAIN: 0x3ffaff78   08 0a 10 02                                       |....|

• DeSerialize

I (338) MAIN: deserialize: a=10
I (348) MAIN: deserialize: b=2

How to use Protocol Buffers

Install protobuf-c-compiler and c-library in ubuntu

$ sudo apt install protobuf-c-compiler libprotobuf-c-dev
$ protoc-c --version
protobuf-c 1.3.3
libprotoc 3.6.1

Make message define file

$ cat amessage.proto
syntax = "proto2";

message AMessage {
  required int32 a=1;
  optional int32 b=2;
}

Compile message define file

protoc-c generates header files and source code.

$ protoc-c --c_out=. amessage.proto

$ ls amessage.*
amessage.pb-c.c  amessage.pb-c.h  amessage.proto

Copy header files and source code to your project

$ cp amessage.pb-c.* /your_project/main/

Include header files to your source

#include "amessage.pb-c.h"

Add source file to your CMakeLists.txt

set(component_srcs main.c amessage.pb-c.c)

About proto3 description format

proto3 is not supported.
An error occurs while building the firmware.

../main/main.c:23:12: error: 'AMessage' {aka 'struct _AMessage'} has no member named 'has_b'
   23 |         msg.has_b = 1;
      |            ^
../main/main.c:41:17: error: 'AMessage' {aka 'struct _AMessage'} has no member named 'has_b'
   41 |         if (msg2->has_b) // handle optional field