RBMTX-Lite OpenWrt SDK Exmaple

Prerequisites

You will need:

A PC, laptop or virtual machine running Linux OS (preferably Debian/Ubuntu distro)
An SDK intended for your router, which can be downloaded here: Software Development Kit

Preparation

Create a directory where the SDK will be extracted, e.g. RBMTX_SDK.
Open a terminal in the folder you created and unzip the SDK.

tar -xf ~/Downloads/rbmtx3-owrt-sdk-....Linux-x86_64.tar.xz

Go to the SDK directory.

cd rbmtx3-owrt-sdk-22.10.14-rbmtx3_gcc-8.4.0_musl_eabi.Linux-x86_64/

Update the feeds.

./scripts/feeds update -a

Compiling a custom package

In this example, we are going to show you how to generate OpenWrt package based on the simple Modbus client and server application.

Install dependency library (in this example, it is libmodbus). To install library run:
```
./scripts/feeds install libmodbus
```
To create your custom package, when you are in the SDK directory go to the package directory.
```
cd package
```
Make a new directory where the package Makefile should be placed.
```
 mkdir modbus_server
 cd modbus_server
```
Create the Makefile file to build your custom package. Example Makefile is shown below.
- It is important to change all modbus_server strings with your package name.
- In the SOURCE_DIR section add path to your package sources.
- If you are using external library, it is important to complete the dependency sections e.g.:
```
TARGET_LDFLAGS=-lmodbus
DEPENDS:= +libmodbus
PKG_BUILD_DEPENDS+= libs/libmodbus
```
Now we are ready to select the packages and libraries which we want to compile. Return to the SDK root directory and execute the command:
```
 make menuconfig
```
You should see a view like the one below.
Then turn off the Cryptographically sign package lists option in the Global build settings
Then go to the Libraries section and make sure the libraries you want to use are checked.
Next, go to the section where you placed the package to compilation. The name of section depends on the name that was placed in the CATEGORY: option in the package's Makefile. In our case it is Example section. Make sure your custom package is checked.
At the end, save all settings - leave the default name of the configuration.
Exit the menuconfig.
Now, we are ready to compile our custom package. Type command make in the terminal and wait for compilation to finish. You should see the output like the one below:
Once the compilation process is complete, the package can be found in the bin/packages/arm_cortex-a7_neon/base directory.
```
cd bin/packages/arm_cortex-a7_neon/base
```