Tutorial 1: Manually building a binary for the device

Overview

This tutorial will show you how to build classic "Hello world" application suitable to run on device and run it.

It is assumed that you've set up development environment as described in Documentation/BuildEnvironment.

Introduction

Unlike regular development when both compiler and program are run on same machine, embedded development uses cross-compilation — compiler is run on your PC, and it produces binaries for target platform.

GNU toolchain (in use by OpenInkpot) uses prefixes to distinguish native and cross-compilers: mipsel-ip-linux-gnu-gcc or arm-ip-linux-gnueabi-gcc, same applies to ld, ar and other tools.

Development environment

After setting up development environment you should have executable file enter in the root of directory you choose. Let's enter the development environment:

[user@host] $ cd $chroot # name of development environment directory
[user@host] $ ./enter
build@host:~$ 

As you see, the prompt has changed. You've been chrooted into a separated Linux environment (Debian stable) with a set of tools for cross-compilation and OpenInkpot-specific helpers.

Let's check that cross-compiler is here (use arm-ip-linux-gnueabi-gcc for V3 and other ARM-based devices):

build@host:~$ mipsel-ip-linux-gnu-gcc --version
mipsel-ip-linux-gnu-gcc (Debian 4.3.2-1.ip2) 4.3.2
...
build@host:~$

If there is no cross-compiler, then install it (armel-cross-toolchain for ARM-based devices):

build@host:~$ sudo apt-get install mipsel-cross-toolchain
...
build@host:~$

Hello world

Using your favorite editor, create helloworld.c with the famous content:

#include <stdio.h>

int main()
{
    printf("Hello world!\n");
    return 0;
}

Compilation

Copy the helloworld.c to home directory of build user in development environment:

[user@host] $ cp helloworld.c $chroot/build

Compile helloworld (again, use arm-ip-linux-gneabi-gcc for ARM-based devices):

build@host:~$ mipsel-ip-linux-gnu-gcc -o helloworld helloworld.c
build@host:~$ file helloworld
helloworld: ELF 32-bit LSB executable, MIPS, MIPS-I version 1 (SYSV), dynamically linked (uses shared libs),
for GNU/Linux 2.6.8, with unknown capability 0xf41 = 0x756e6700, stripped
build@host:~$

Running

As you see, helloworld is a binary for MIPS (or ARM) architecture. Copy it to device and run:

[user@host] $ rsync $chroot/build/helloworld 192.168.111.1:
[user@host] $ ssh root@192.168.111.1
/mnt/storage/.home/user # ./helloworld
Hello world!
/mnt/storage/.home/user #

It works!

Further reading

Proceed to next tutorial for learning how to deal with shared libraries on OpenInkpot.