Tutorial on how to write an OSD plugin

A tutorial by Alexey Belyaev.

A short instruction on how to assemble plugins, using the example of OSD Plugin for RubyFPV

Ideally, it is better to use Linux or Darvin for assembly, but it also builds perfectly on Windows.

For assembly we need:

1.       Source code RubyFPV (https://github.com/PetruSoroaga/RubyFPV)

2.       Source code of OSD Plugin (https://github.com/.../code/r_plugins_osd/my_plugin_source.cpp)

3.       Make tool packet for build control (for Windows: https://gnuwin32.sourceforge.net/packages/make.htm)

4.       GCC for ARM AArch32 target with hard float arm-none-linux-gnueabihf (for Widows: https://developer.arm.com/downloads/-/gnu-a)

5.       Developer IDE VSCode (https://code.visualstudio.com/download)

That seems to be all.

Note: I've heard a lot of opinions and seen a lot of instructions where the authors claim that a “special” compiler is needed to build for Raspberry, but in practice everything is much simpler. Suitable universal for ARM.

I will not tell you how to install the packages described above, this is not what this instruction is about. They are assumed to be installed.

The minimum set of source code consists of 2 files of the plugin itself and the RubyFPV source code:


The file my_plugin_source.cpp contains the code of the plugin itself, in this case it is completely the same code from the “RubyFPV source package”

But the Makefile file requires special attention, its contents are the following:



PREFIX := arm-linux-gnueabihf-

GPP := $(PREFIX)g++

GCC := $(PREFIX)gcc

PLATFORM = -march=armv7-a -mfloat-abi=hard -mfpu=neon-vfpv4


INCLUDES += -I../../RubyFPV/code


LDFLAGS= -lrt -lpthread -lc -shared $(LIBS)

CFLAGS += $(PLATFORM) -fno-stack-protector -Wall -O0 -D _GNU_SOURCE -Wno-address-of-packed-member $(INCLUDES)

CPPFLAGS= $(PLATFORM) $(CFLAGS) --std=gnu++17


OUTPUT := build


.PHONY: clean all

all: my_plugin


$(OUTPUT)/%.o: %.cpp mk-dirs

    $(GPP) $(CPPFLAGS) -c -o $@ $<


my_plugin: $(OUTPUT)/my_plugin_source.o mk-dirs

    $(GCC) $(CFLAGS) $(LDFLAGS) $(OUTPUT)/my_plugin_source.o -Wl,-soname, my_plugin.so.$(VER_MAJOR) -o $(OUTPUT)/my_plugin.so.$(VERSION)



    mkdir ./$(OUTPUT)



    rm -fr $(OUTPUT)


Note: I do not pretend that the example has the only one correct solution.

Let's take a closer look at the important points:

1.       VER_MAJOR and VERSION variables for easy maintenance of the plugin version

2.       PREFIX it is necessary to set the “prefix” of the GCC executable files for assembly for the ARM platform, for the case of Raspberry Pi this is AArch32 with hard float

3.       PLATFORM compiler switches, specifying the hard float option and the architecture of a specific processor.

The above keys will allow you to collect the “correct” binary code from any system.

1.       -Wno-address-of-packed-member key required to hide warnings when building mavlink (https://mavlink.io/en/mavgen_c/#waddress-of-packed-member) in case your plugin will use its functionality.

The plugin is built normally using the make all commands, there are no special features here.
Now a little about the ease of development. VSCode and several plugins will help us with this.

In my opinion the minimum set is:

1.       C/C++ (https://marketplace.visualstudio.com/items?itemName=ms-vscode.cpptools)

2.       C/C++ Extension Pack (https://marketplace.visualstudio.com/items?itemName=ms-vscode.cpptools-extension-pack)

3.       Makefile Tools (https://marketplace.visualstudio.com/items?itemName=ms-vscode.makefile-tools)

4.       Better C++ Syntax (https://marketplace.visualstudio.com/items?itemName=jeff-hykin.better-cpp-syntax)

Also in the project you need to create a file .vscode/c_cpp_properties.json with the following contents:


    "configurations": [


            "name": "Raspberry",

            "includePath": [




            "defines": [



            "compilerPath": "arm-linux-gnueabihf-g++.exe",

            "cppStandard": "gnu++17",

            "intelliSenseMode": "linux-gcc-arm",

            "configurationProvider": "ms-vscode.makefile-tools",

            "cStandard": "gnu17",

            "mergeConfigurations": false,

            "browse": {

                "path": [




                "limitSymbolsToIncludedHeaders": true




    "version": 4



The result should look something like this:

You can see that code addition works and you can move on to methods from the main RubyFPV code