Xenomai on the Beaglebone Black in 14 easy steps


EDIT: Mark wrote an updated guide here.

The BeagleBone Black is an amazingly cheap and powerful development platform that is being used by many people in a lot of projects. That was intentionally vague, because I know that if you ended up here you already know what a BeagleBone Black is.

In this post I’ll explain how I got Xenomai to run on my BeagleBone.

First of all I tried these instructions, but couldn’t get past the kernel compilation step. I believe that this is due to the instructions being six months old, which are like two and a half centuries in computer time. So I continued searching and found a post in a Japanese blog. Using my fluent Japanese Google Translator I could understand what was going on and could successfully reproduce the steps and get Xenomai up and running (big thanks to the author!). Here I’ll reproduce the steps. I’m assuming that you are on a computer running Ubuntu (like mine) and are familiar with the command line.

Getting the tools

Step 0: Get all the tools that will be needed (cross-compiler and dev libraries).

sudo apt-get install build-essential libncurses5{,-dev} gcc-arm-linux-gnueabi

Building the Kernel

Step 1: First of all, make a directory to hold all of our development files. I’ll call mine bbb.

mkdir bbb
cd bbb
export BBB=$(pwd)

Step 2: Get the Linux kernel for the BeagleBone and the Xenomai sources. This might take a while.

git clone http://github.com/beagleboard/kernel.git beagle-kernel
wget http://download.gna.org/xenomai/stable/xenomai-2.6.3.tar.bz2
tar xvjf xenomai-2.6.3.tar.bz2

Step 3: Checkout kernel 3.8 version branch. Apply BeagleBone’s patches.

Note: In this step I revert to a specific commit because newer ones are known to cause problems.

cd beagle-kernel
git checkout origin/3.8 -b 3.8
git reset --hard eae56c3
./patch.sh

Step 4: Get a firmware that the kernel config will need (I’m not sure whether this firmware is really needed).

wget "http://arago-project.org/git/projects/?p=am33x-cm3.git;a=blob_plain;f=bin/am335x-pm-firmware.bin;hb=HEAD" -O kernel/firmware/am335x-pm-firmware.bin

Step 5: Copy the BeagleBone default config as the running config.

cp configs/beaglebone kernel/.config

Step 6: Apply I-pipe patches to the BeagleBone kernel.

cd kernel
patch -p1 < ../../xenomai-2.6.3/ksrc/arch/arm/patches/beaglebone/ipipe-core-3.8.13-beaglebone-pre.patch
patch -p1 < ../../xenomai-2.6.3/ksrc/arch/arm/patches/ipipe-core-3.8.13-arm-3.patch
patch -p1 < ../../xenomai-2.6.3/ksrc/arch/arm/patches/beaglebone/ipipe-core-3.8.13-beaglebone-post.patch

Step 7: Run the Xenomai prepare-kernel  script for the BeagleBone kernel.

cd ../../xenomai-2.6.3/scripts
./prepare-kernel.sh --arch=arm --linux=../../beagle-kernel/kernel

Step 8: Configure the kernel to be built.

cd ../../beagle-kernel/kernel
make ARCH=arm menuconfig

Under CPU Power Management --->  CPU Frequency scaling, disable [ ] CPU Frequency scaling(Note: Don’t know if it’s better to leave it enabled, read the comments!)

Under Real-time sub-system  ---> Drivers ---> Testing drivers, enable everything.

Step 9: Compile the kernel.

Note: I chose 16 to the -j  option, because my computer has 8 cores. Choose a value appropriate to your computer. I read somewhere that 2 times the number of cores is a good number.

Note: If there were errors in the compilation, the messages will probably be lost among all other output. To see them, simply run the command again.

make -j16 ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- LOADADDR=0x80008000 uImage dtbs modules

Preparing an SD Card

Now let’s get an SD Card ready with the Angstrom distribution and our kernel. If you want to use this kernel with the distribution on the eMMC memory, just put it in the appropriate place.

Step 10: Download and copy the default Angstrom distribution to your SD Card. Replace /dev/sdX  with the path to your SD Card. sudo fdisk -l  is your friend. Note: I used a SanDisk 4GB SD Card.

CAUTION: YOU WILL LOSE ALL YOUR PREVIOUS DATA ON THE DEVICE /dev/sdX !

cd $BBB
wget https://s3.amazonaws.com/angstrom/demo/beaglebone/Angstrom-Cloud9-IDE-GNOME-eglibc-ipk-v2012.12-beaglebone-2013.06.20.img.xz
sudo -s
xz -dkc Angstrom*img.xz > /dev/sdX
exit

Step 11: Mount the Angstrom partition. Copy kernel and kernel modules (thanks for your comment, Jurg Lehni!), Xenomai modules and source folder to that partition. Replace /dev/sdX2 with your actual path to the partition.

mkdir sd
sudo mount /dev/sdX2 sd
sudo cp beagle-kernel/kernel/arch/arm/boot/uImage sd/boot/uImage-3.8.13
cd beagle-kernel/kernel
sudo make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- INSTALL_MOD_PATH=$BBB/sd modules_install
cd -
mkdir sd/home/root/xeno_drivers
cp beagle-kernel/kernel/drivers/xenomai/testing/*.ko sd/home/root/xeno_drivers/
cp -r xenomai-2.6.3 sd/home/root
sudo umount sd

Testing

Now put the SD card on the BeagleBone, boot it, ssh into it and test Xenomai.

Step 12: Configure the date and compile Xenomai

Note: an example for the date command would be date -s "21 May 2014 13:25 GMT-3" 

date -s "DD MMM YYYY HH:MM TZ"
cd ~/xenomai-2.6.3
./configure CFLAGS="-march=armv7-a -mfpu=vfp3" LDFLAGS="-march=armv7-a -mfpu=vfp3"
make
make install

Step 13: Load the testing driver

cd ~/xeno_drivers
insmod xeno_klat.ko

Step 14: Run some tests!

User-mode latency:

# /usr/xenomai/bin/latency
== Sampling period: 1000 us
== Test mode: periodic user-mode task
== All results in microseconds
warming up...
RTT|  00:00:01  (periodic user-mode task, 1000 us period, priority 99)
RTH|----lat min|----lat avg|----lat max|-overrun|---msw|---lat best|--lat worst
RTD|      6.916|      7.083|     11.708|       0|     0|      6.916|     11.708
RTD|      6.874|      8.041|     22.708|       0|     0|      6.874|     22.708
RTD|      8.749|      9.041|     28.333|       0|     0|      6.874|     28.333
RTD|      8.791|      9.041|     22.583|       0|     0|      6.874|     28.333
RTD|      8.791|      9.083|     26.499|       0|     0|      6.874|     28.333
RTD|      8.791|      9.041|     24.541|       0|     0|      6.874|     28.333
RTD|      8.708|      8.999|     25.208|       0|     0|      6.874|     28.333
RTD|      8.833|      9.041|     24.041|       0|     0|      6.874|     28.333
RTD|      8.749|      9.041|     26.291|       0|     0|      6.874|     28.333
RTD|      8.791|      8.999|     22.416|       0|     0|      6.874|     28.333
^C---|-----------|-----------|-----------|--------|------|-------------------------
RTS|      6.874|      8.708|     28.333|       0|     0|    00:00:10/00:00:10

In-kernel Latency:

# /usr/xenomai/bin/klatency
== Sampling period: 100 us
== Test mode: in-kernel periodic task
== All results in microseconds
warming up...
RTT|  00:00:00  (in-kernel periodic task, 100 us period, priority 99)
RTH|-----lat min|-----lat avg|-----lat max|-overrun|----lat best|---lat worst
RTD|      -3.250|      -0.846|       3.791|       0|      -4.250|       5.167
RTD|      -0.917|      -0.800|       4.041|       0|      -4.250|       5.167
RTD|      -0.917|      -0.801|       4.333|       0|      -4.250|       5.167
RTD|      -1.084|      -0.806|       1.499|       0|      -4.250|       5.167
RTD|      -1.043|      -0.788|       3.999|       0|      -4.250|       5.167
RTD|      -3.335|      -0.794|       3.624|       0|      -4.250|       5.167
RTD|      -0.918|      -0.744|       4.707|       0|      -4.250|       5.167
RTD|      -0.919|      -0.803|       4.581|       0|      -4.250|       5.167
RTD|      -0.877|      -0.797|       4.581|       0|      -4.250|       5.167
RTD|      -0.919|      -0.804|       3.373|       0|      -4.250|       5.167
RTD|      -0.919|      -0.802|       4.622|       0|      -4.250|       5.167
RTD|      -0.920|      -0.804|       3.372|       0|      -4.250|       5.167
^CRTD|      -0.920|      -0.801|       3.622|       0|      -4.250|       5.167
---|------------|------------|------------|--------|-------------------------
RTS|      -4.250|      -0.744|       5.167|       0|    00:00:06/00:00:06

Poke around:

# cat /proc/xenomai/version
2.6.3
# cat /proc/ipipe/version
3

Change parameters:

# cat /proc/xenomai/latency
4999
# echo "0" >> /proc/xenomai/latency
# cat /proc/xenomai/latency
0
# rmmod xeno_lat
# cd ~/xeno_drivers
# insmod xeno_klat.ko
# /usr/xenomai/bin/klatency
== Sampling period: 100 us
== Test mode: in-kernel periodic task
== All results in microseconds
warming up...
RTT|  00:00:01  (in-kernel periodic task, 100 us period, priority 99)
RTH|-----lat min|-----lat avg|-----lat max|-overrun|----lat best|---lat worst
RTD|       4.041|       4.190|       9.958|       0|       4.041|      10.166
RTD|       3.582|       4.205|      10.374|       0|       3.582|      10.374
RTD|       4.082|       4.191|       8.957|       0|       3.582|      10.374
RTD|       4.082|       4.182|       9.665|       0|       3.582|      10.374
RTD|       4.082|       4.197|       8.373|       0|       3.582|      10.374
RTD|       3.623|       4.193|       8.457|       0|       3.582|      10.374
RTD|       3.915|       4.184|       9.040|       0|       3.582|      10.374
RTD|       4.081|       4.184|       8.206|       0|       3.582|      10.374
RTD|       0.456|       4.180|       8.664|       0|       0.456|      10.374
RTD|       0.455|       4.196|       8.831|       0|       0.455|      10.374
RTD|       4.080|       4.182|       8.997|       0|       0.455|      10.374
RTD|       4.080|       4.197|       9.622|       0|       0.455|      10.374
RTD|       4.038|       4.187|       9.913|       0|       0.455|      10.374
RTD|       4.079|       4.194|       8.788|       0|       0.455|      10.374
RTD|       4.079|       4.181|       8.538|       0|       0.455|      10.374
RTD|       4.079|       4.175|       8.579|       0|       0.455|      10.374
^CRTD|       0.704|       4.195|       9.079|       0|       0.455|      10.374
---|------------|------------|------------|--------|-------------------------
RTS|       0.455|       3.967|      10.374|       0|    00:00:17/00:00:17

Great, huh? Now go develop something real time =)

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