Creating a minimal Raspbian based LinuxCNC image for Raspberry Pi

1. Prerequisites

This build is based on the assumption that the host is running on a Debian based system or its derivatives. This procedure was created and tested on a Debian Wheezy host.

2. Build Xenomai kernel

The following steps were performed on a host computer. The kernel can also be built natively, in this case skip the installation of the cross compiler.

2.1. Install cross compiler

Download and untar the crosscompiler from https://github.com/raspberrypi/tools/archive/master.tar.gz

	cd <working dir>
	wget https://github.com/raspberrypi/tools/archive/master.tar.gz
	tar xzf master.tar.gz

2.2. Download source files and patches

Download kernel

	git clone -b rpi-3.2.27 --depth 1 git://github.com/raspberrypi/linux.git linux-rpi-3.2.27

Download firmware

	git clone https://github.com/raspberrypi/firmware.git

Download Xenomai

	wget http://download.gna.org/xenomai/stable/xenomai-2.6.1.tar.bz2
	tar xjf xenomai-2.6.1.tar.bz2

Download patches

	mkdir patch
	wget http://www.cim.mcgill.ca/~ian/rpi-linux-3.2.21-xenomai-2.6.1.patch -P patch
	wget http://dl.dropbox.com/u/17024524/linuxcnc/rpi-3.2.27-xenomai.patch -P patch

2.3. Apply patches

Apply 3.2.27 patch

	patch -p0 < patch/rpi-3.2.27-xenomai.patch

Apply Xenomai 2.6.1 patch

	xenomai-2.6.1/scripts/prepare-kernel.sh --arch=arm --linux=linux-rpi-3.2.27 --adeos=xenomai-2.6.1/ksrc/arch/arm/patches/ipipe-core-3.2.21-arm-1.patch

Apply Raspberry Pi Xenomai patch

	(cd linux-rpi-3.2.27; patch -p1 < ../patch/rpi-linux-3.2.21-xenomai-2.6.1.patch)

2.4. Compile kernel

Create build directory

	mkdir linux-rpi-3.2.27/build

Configure kernel

	cd linux-rpi-3.2.27
	make mrproper
	make ARCH=arm O=build menuconfig

Or download and use a minimal configuration file

	wget http://dl.dropbox.com/u/17024524/linuxcnc/config.rpi-3.2.27-xenomai%2B -O linux-rpi-3.2.27/build/.config
	cd linux-rpi-3.2.27
	make mrproper
	make ARCH=arm O=build oldconfig

Compile

	make ARCH=arm O=build CROSS_COMPILE=../../tools-master/arm-bcm2708/arm-bcm2708hardfp-linux-gnueabi/bin/arm-bcm2708hardfp-linux-gnueabi-

Install modules

	make ARCH=arm O=build INSTALL_MOD_PATH=dist modules_install

Install headers

	make ARCH=arm O=build INSTALL_HDR_PATH=dist headers_install
	find build/dist/include \( -name .install -o -name ..install.cmd \) -delete

The linux-rpi-3.2.27/build/dist directory contains the kernel headers and modules while the kernel image is at linux-rpi-3.2.27/build/arch/arm/boot/ .

3. Create minimal Raspbian image

The Raspbian image is created using debootstrap and QEMU. These steps can also be performed on a Raspberry Pi.

3.1. Install required packages

On host PC

	sudo apt-get install qemu qemu-user qemu-user-static binfmt-support debootstrap

Or on RPi

	sudo apt-get install debootstrap

3.2. Build image using debootstrap

Select an appropriate Raspbian mirror at http://www.raspbian.org/RaspbianMirrors

On host PC

	cd <working dir>
	sudo debootstrap --foreign --no-check-gpg --include=ca-certificates --arch=armhf wheezy rootfs <Raspbian mirror>

Edit /etc/qemu-binfmt.conf, add the following line:

		EXTRA_OPTS="-L/usr/lib/arm-linux-gnueabihf"

	sudo cp $(which qemu-arm-static) rootfs/usr/bin
	sudo chroot rootfs/ /debootstrap/debootstrap --second-stage --verbose

add the raspbian mirror used to /etc/apt/sources.list

	sudo sh -c 'echo deb <Raspbian mirror> wheezy main > rootfs/etc/apt/sources.list'

Or on RPI

	cd <working dir>
	sudo debootstrap --no-check-gpg --include=ca-certificates wheezy rootfs <Raspbian mirror>

3.3. Configure Raspbian

Edit /etc/hostname

	sudo sh -c 'echo rpi-linuxcnc >rootfs/etc/hostname'

Edit /etc/hosts

	sudo sh -c 'echo -e 127.0.0.1\\trpi-linuxcnc >> rootfs/etc/hosts'

Edit network interface

	sudo sh -c 'cat> rootfs/etc/network/interfaces << EOF
	auto lo
	iface lo inet loopback

	auto eth0
	iface eth0 inet dhcp
	EOF
	'

Edit /etc/fstab

	sudo sh -c 'cat> rootfs/etc/fstab << EOF
	proc /proc proc defaults 0 0
	/dev/mmcblk0p1 /boot vfat defaults 0 0
	EOF
	'

Create /etc/resolv.conf

	sudo cp /etc/resolv.conf rootfs/etc

Chroot

	sudo chroot rootfs /bin/bash

Set locale to ignore warnings

	LC_ALL=C
	LANGUAGE=C
	LANG=C

Install required packages

	apt-get update
	apt-get install --no-install-recommends locales sudo xauth bc openssh-server ntp gettext autoconf \
		libpth-dev gcc g++ make git libncurses5-dev libreadline-gplv2-dev tcl8.5-dev tk8.5-dev bwidget \
		blt libxaw7-dev libglu1-mesa-dev libgl1-mesa-dev libgtk2.0-dev python python-dev python-support \
		python-tk python-lxml libboost-python-dev yapps2-runtime libtk-img python-imaging python-imaging-tk \
		libgl1-mesa-swx11 python-xlib python-gtkglext1 python-configobj python-glade2 python-numpy build-essential

Cleanup Apt cache

	apt-get clean

Create xenomai group

	addgroup xenomai
	addgroup root xenomai

Create new user

	adduser rpi
	usermod -a -G xenomai,sudo,staff,kmem rpi

Configure udev rules

	cat >/etc/udev/rules.d/xenomai.rules<<EOF
	# allow RW access to /dev/mem
	KERNEL=="mem", MODE="0660", GROUP="kmem" 
	# real-time heap device (Xenomai:rtheap)
	KERNEL=="rtheap", MODE="0660", GROUP=="xenomai"
	# real-time pipe devices (Xenomai:rtpipe)
	KERNEL=="rtp[0-9]*", MODE="0660", GROUP="xenomai"
	EOF

Exit chroot

	exit

Install Xenomai kernel modules and headers

	sudo cp -a linux-rpi-3.2.27/build/dist/lib/modules rootfs/lib/
	sudo cp -a linux-rpi-3.2.27/build/dist/include/* rootfs/usr/include
	sudo cp linux-rpi-3.2.27/build/.config rootfs/boot/config-3.2.27-xenomai+

4. Build LinuxCNC

Compiling is done under the chroot environment. These steps are the same for both host PC and RPi.

Copy sources

	sudo cp -a xenomai-2.6.1 rootfs/usr/src
	git clone -b rtos-integration-preview3 --depth 1 git://git.mah.priv.at/emc2-dev.git
	sudo cp -a emc2-dev rootfs/usr/src/

Chroot

	sudo chroot rootfs

Ignore locale warnings

	LC_ALL=C
	LANGUAGE=C
	LANG=C

Compile and install Xenomai

	cd /usr/src/xenomai-2.6.1
	./configure
	make DESTDIR=$(pwd)/rpi install
	tar cf - -C rpi usr/xenomai/{bin,lib,sbin,include} | tar xvf - -C /
	echo /usr/xenomai/lib/ > /etc/ld.so.conf.d/xenomai.conf
	ldconfig -v

Cleanup Xenomai

	make clean
	rm -r rpi

Compile and install LinuxCNC

	cd ../emc2-dev/src
	./autogen.sh
	./configure --prefix=/usr/local --with-platform=raspberry --disable-build-documentation --with-kernel=/boot/config-3.2.27-xenomai+
	make
	make install

Cleanup LinuxCNC

	make clean

Exit chroot

	exit

Cleanup QEMU

	sudo rm rootfs/usr/bin/qemu-arm-static

5. Create SD card image

This section will create a 2GB SD image This section creates a 2GB SD image file

Create sparse file

	cd <working dir>
	dd if=/dev/zero of=rpi-lcnc.img count=0 bs=1 seek=2021654528

Create partitions

	sudo sh -c 'cat <<EOF | sfdisk --force rpi-lcnc.img
	unit: sectors

	1 : start=     2048, size=   204800, Id= c
	2 : start=   206848, size=  3741696, Id=83
	EOF
	'

Format partitions

	sudo losetup /dev/loop0 rpi-lcnc.img -o $((2048*512))
	sudo mkfs.vfat -F 32 -n BOOT /dev/loop0
	sudo losetup -d /dev/loop0
	sudo losetup /dev/loop0 rpi-lcnc.img -o $((206848*512))
	sudo mkfs.ext4 -L ROOT /dev/loop0
	sudo losetup -d /dev/loop0

Mount partitions

	mkdir -p mnt/{boot,root}
	sudo mount -o loop,offset=$((2048*512)) rpi-lcnc.img mnt/boot
	sudo mount -o loop,offset=$((206848*512)) rpi-lcnc.img mnt/root

Populate ROOT

	sudo rsync -a rootfs/ mnt/root/
	sudo cp -a firmware/hardfp/opt/vc mnt/root/opt/

Populate BOOT

	sudo mv rootfs/boot/* mnt/boot/
	sudo cp firmware/boot/{*bin,*dat,*elf} mnt/boot/
	sudo cp linux-rpi-3.2.27/build/arch/arm/boot/Image? mnt/boot/kernel.img
	sudo sh -c 'cat >mnt/boot/config.txt<<EOF
	kernel=kernel.img
	arm_freq=800
	core_freq=250
	sdram_freq=400
	over_voltage=0
	gpu_mem=16
	EOF
	'
	sudo sh -c 'cat >mnt/boot/cmdline.txt<<EOF
	xeno_nucleus.xenomai_gid=1000 dwc_otg.lpm_enable=0 console=ttyAMA0,115200 kgdboc=ttyAMA0,115200 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline rootwait
	EOF
	'

Unmount partitions

	sudo umount mnt/{boot,root}

Compress image

	bzip2 -9 rpi-lcnc.img

Install image

	sudo sh -c 'bzcat rpi-lcnc.img.bz2 > /dev/<sdcard>'

6. Post-install

Configure locale

	sudo dpkg-reconfigure locales

Configure timezone

	sudo dpkg-reconfigure tzdata

7. Testing

SSH to RPi

	ssh -X -l rpi <ip address>

Xenomai latency test

	sudo sh -c 'echo 3500 > /proc/xenomai/latency'
	/usr/xenomai/bin/latency

LinuxCNC latency test

	latency-test 100us 1ms

8. Pre-built image

Note: The first boot will take a while since the SSH keys are being generated

This pre-built image does not have libgl1-mesa-swx11 installed (this package is needed by Axis)

Download

       [rpi-lcnc.img]

or

	http://filecloud.io/_0vew6zmj

	Username: rpi
	Password: linuxcnc

9. References

http://wiki.debian.org/Debootstrap

http://www.blaess.fr/christophe/2012/08/27/xenomai-sur-raspberry-pi/

http://www.raspberrypi.org/phpBB3/viewtopic.php?f=41&t=12368

http://www.raspberrypi.org/phpBB3/viewtopic.php?f=37&t=14122

http://wrttn.in/59e640

RaspbianXenomaiBuild