Embedded Systems: Cross Compilation

Using host machine to compile codes that is active on target machine.

Setup

• Host machine
  • OS: ubuntu 18.04 native
• Target machine
  • raspberry pi 3b+

Getting Toolchain

	sudo apt install gcc-arm-linux-gnueabihf

This command installs gcc working on:

• arm processor
• EABI is hard (gcc -mfloat-abi=hard)

Crosstool-NG

download

wget http://crosstool-ng.org/download/crosstool-ng/crosstool-ng-1.24.0.tar.xz

decompress by

tar -xvf crosstool-ng-1.24.0.tar.xz

for required packages

sudo apt install autoconfflex bison texinfohelp2man gawk libtool-bin

curses

sudo apt-get install libncurses5-dev libncursesw5-dev

configure by

./configure

in decompressed dir.

make by:

make
sudo make install

check configurations

list up

ct-ng list-samples

check specific configuration

ct-ng arm-unknown-linux-gnueabi

adjust configuration by

ct-ng menuconfig

build

ct-ng build

hello world

After finishing the process above, toolchain is located in:

~/x-tools/arm-unknown-linux-gnueabi/bin

so setup the path by:

export PATH=$PATH:~/x-tools/arm-unknown-gnueabi/bin

This exported path is initialized after logout. So if you want to permantly set path, you can add export command above to the ’~/.bashrc file. Just add the line above and save it.

and can create hello.c as:

#include <stdio.h>

int main(void){
	int value;
	printf("Hello Raspberry Pi!");
	printf("type an integer value:");
	scanf("%d", &value);
	printf("Input value: %d %x \n", value, value);
	return 0;
}

and compile by

arm-unknown-linux-gnueabi-gcc hello.c -o hello

However, this cannot be executed, as we are on host machine, not on target machine.

Enable SSH

In host machine, we do the followings.

Raspbian boot SD card is consist of two parts:

• FAT32 with bootloader, kernel.bin, Config.txt @ /dev/sdb1 for me
• ext4 with Raspbian File System @ /dev/sdb2 for me

For native ubuntu, plug in usb-sdcard adapter. and setup the first partition by:

mkdir sdcard1
sudo mount /dev/sdb1 sdcard1
echo "" > sdcard1/ssh
sudo umount sdcard1

second partition by,

mkdir sdcard2
sudo mount /dev/sdb2 sdcard2

and can edit by:

vim sdcard2/etc/dhcpcd.conf

and uncomment or add by:

interface eth0
static ip_address=192.168.1.10/24

and umount by

sudo umount sdcard2 

Host setup

I used ethernet cable / adapter to connect host and target machine.

Network for host machine: 192.168.1.1

Network for target machine: 192.168.1.10/24 as set in dhcpcd.conf

connect by ssh

ssh pi@192.168.1.10

and default password is raspberry.

Send files

scp hello pi@192.168.1.10:~/

Execute in target machine

Through ssh mode,

./hello