RBMTX-Lite OpenWrt SDK Exmaple

Prerequisites

You will need:

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

Preparation

1. Create directory, where the SDK will be extrated e.g RBMTX_SDK.
2. Open terminal in created folder and unpack SDK.

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

3. Go to the SDK directory.

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

4. 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 base on the simple Modbus client and server application.

1. To create custom package, when you are in the SDK directory go to the package directory.

   cd package

2. Make new directory where the package Makefile should be placed.

    mkdir modbus_server
    cd modbus_server

3. Create the Makfile file to build your custom package. Exmaple Makefile shown below.

include $(TOPDIR)/rules.mk

# Name, version and release number
# The name and version of your package are used to define the variable to point to the build directory of your package: $(PKG_BUILD_DIR)
PKG_NAME:=helloworld
PKG_VERSION:=1.0
PKG_RELEASE:=1

# Source settings (i.e. where to find the source codes)
# This is a custom variable, used below
SOURCE_DIR:=/home/build/helloworld

include $(INCLUDE_DIR)/package.mk

# Package definition; instructs on how and where our package will appear in the overall configuration menu ('make menuconfig')
define Package/helloworld
  SECTION:=examples
  CATEGORY:=Examples
  TITLE:=Hello, World!
endef

# Package description; a more verbose description on what our package does
define Package/helloworld/description
  A simple "Hello, world!" -application.
endef

# Package preparation instructions; create the build directory and copy the source code. 
# The last command is necessary to ensure our preparation instructions remain compatible with the patching system.
define Build/Prepare
		mkdir -p $(PKG_BUILD_DIR)
		cp $(SOURCE_DIR)/* $(PKG_BUILD_DIR)
		$(Build/Patch)
endef

# Package build instructions; invoke the target-specific compiler to first compile the source file, and then to link the file into the final executable
define Build/Compile
		$(TARGET_CC) $(TARGET_CFLAGS) -o $(PKG_BUILD_DIR)/helloworld.o -c $(PKG_BUILD_DIR)/helloworld.c
		$(TARGET_CC) $(TARGET_LDFLAGS) -o $(PKG_BUILD_DIR)/$1 $(PKG_BUILD_DIR)/helloworld.o
endef

# Package install instructions; create a directory inside the package to hold our executable, and then copy the executable we built previously into the folder
define Package/helloworld/install
		$(INSTALL_DIR) $(1)/usr/bin
		$(INSTALL_BIN) $(PKG_BUILD_DIR)/helloworld $(1)/usr/bin
endef

# This command is always the last, it uses the definitions and variables we give above in order to get the job done
$(eval $(call BuildPackage,helloworld))