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 extrated, e.g. RBMTX_SDK.
Open a terminal in the folder you created folder 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 library. 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 Makfile file to build your custom package. Exmaple Makefile shown below.
- It is important to change all modbus_server string with your package name.
- In the SOURCE_DIR section add path to your package sources.
- If you use 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 command:
```
 make menuconfig
```
You should see a view like in the picture below.
Then turn off in the Global build settings option Cryptographically sign package lists
Then go to the Libraries section and make sure the libraries you want to use are checked.
Next go to the section where you pleaced the package to compliation. The name of section depends on the name that was placed in the CATTEGORY: option in the package's Makefile. In our case, it is Example section. Make sure that your castom package is checked.
At the end, save all settings - leave the default name of the configuration.
Exit the menuconfig.
Now, we are ready to complie our custom package. Type comamnd make in the terminal and wait for compilation finish. You should see the output like in the picture below:
Once the compilation process is complete, the package can be found in the directory bin/packages/arm_cortex-a7_neon/base.
```
cd bin/packages/arm_cortex-a7_neon/base
```