Compiling programs for OpenWRT
When I was trying to compile my first OpenWRT program I searched around the web, but didn’t found any useful (at least to me) tutorials/guides that would help me. After spending a few hours behind a computer and figuring out how to do this I found the easiest way to do it.
The are two ways of compiling:
- simply compiling your application
- building a package for it
Differences? If you have a package it’s easier to install and uninstall it, and probably easier to update it. However, in most of my cases I just simply want to compile my source code to a single executable and copy it to the device. Here I will show you the easiest way to do it and go from source code to final executable in a few minutes.
What you need?
- Linux distribution
- OpenWRT Toolchain for processor which is in the target device
I’m currently focused on tiny routers called TP-Link WR703n, so my toolchain is available at: http://downloads.openwrt.org/attitude_adjustment/12.09/ar71xx/generic/ For others please visit www.openwrt.org and search for toolchain for your device.
Create folder and put create Makefile similar to this:
export STAGING_DIR= CC=gcc all: clean program cc: CC=$(STAGING_DIR)/bin/mips-openwrt-linux-gcc cc: clean program deploy deploy: scp program email@example.com:/path/to/where/you/want/to/put/your/executable/ program: main.o $(CC) main.o -o program main.o: $(CC) -c main.c clean: rm -rf *.o program
Change path to your toolchain, your device’s IP address, path to where you want to put your executable and name of your C file. If you want to include additional files just copy main.o to something.o, add it to program: section, and change the names accordingly.
If you need to link your program with additional library (e.g. pthread), you can add that to CC variable (e.g. gcc -lpthread).
What can I do with this Makefile?
- command make – compile program for your PC (compile with the toolchain available on your computer and be able to test it out on it)
- command make cc – compile program for OpenWRT device and deploy it to the device
- command make deploy – deploy compiled application to your device
Example file from one of my projects:
export STAGING_DIR=/home/dean/Downloads/OpenWrt-Toolchain-ar71xx-for-mips_r2-gcc-4.6-linaro_uClibc-0.9.33.2/toolchain-mips_r2_gcc-4.6-linaro_uClibc-0.9.33.2 CC=gcc -pthread all: clean lightning-service cc: CC=$(STAGING_DIR)/bin/mips-openwrt-linux-gcc -pthread cc: clean lightning-service deploy deploy: scp lightning-service firstname.lastname@example.org:/apps/ lightning-service: serial_port.o main.o $(CC) serial_port.o main.o -o lightning-service main.o: $(CC) -c main.c serial_port.o: $(CC) -c serial_port.c clean: rm -rf *.o lightning-service
This is an example of Makefile for a program that I use to control stairway lights at home. Lights are connected to my router via Launchpad MSP430 microcontroller, and I can communicate with them through TCP. I am also linking pthread library because I need threads (one for listening/communicating with serial port and one for TCP connections).
This is probably the simplest way you can compile your own programs without having to bother with creating your own packages.