In this project I am responsible for the communications (both, hardware and software/firmware) and most of the electronics (e.g. control boards, custom motor drivers). Unfortunately I can not share any source code or technical details about it, what I would really love to do, we do have a trac set up, so keep checking out here, as we might be allowed to publish them in the future, in meantime here is what I can say: the control boards are powered by an at91sam7 series uC, using Ethernet technology with a custom protocol for fully deterministic communications (i.e. communications are designed in a way that frame collisions can not occur) . Everything runs in real-time using linux-rt kernel on fit-pc2i box.  By now it already has walked (limped?) about two kilometers without any  technical difficulties!

Also, notice it is missing feet and in general a lot of mechanical parts, it is because we assembled it only three days ago, and we are still waiting for some parts to be manufactured. See: newest image

Pics or it didn’t happen (TL; DR;):

Stiffness Adjusters in Action:

[Show as slideshow]

Offtopic: There was a flashmob in The National Museum of Scotland during our presentation, links to follow

Installation

• Installing required packages:

# apt-get install bridge-utils debootstrap

• Setting up a bridge interface:

As I already had bridge set up for OpenVPN, so I skipped this step.
For the most basic bridge add following configuration to /etc/network/interfaces:

# Bridge setup
iface br0 inet static
        bridge_ports eth0 eth1
        address 192.168.0.2
        broadcast 192.168.0.255
        netmask 255.255.255.0
        gateway 192.168.0.1

bridge_ports – specify physical interfaces to be added to br0. You should not put any lines to configure the interfaces that will be used by the bridge, as this will be setup automatically by the scripts when bringing the bridge up.

• Installing LXC:
  Assuming you’re running Debian Stable (squeeze (v6.0) at the time of writing), then the candidate LXC version should be <0.7.3:

  apt-cache policy lxc | grep -i candidate

  All versions up to 0.7.3 (see: bug #601422) by default uses debian lenny distribution for the VM containers. If you are ok with that, go directly to “Using lenny for the container”, otherwise, see below “Using squeeze for the container”.

  • Using squeeze for the container:

The one possible way to get LXC >=0.7.3 with squeeze is to use testing repository, as backports do not include LXC yet. This is more a hack, than a good solution, but because LXC does not have many dependencies it works just fine for our purposes.
Add default release parameter for apt:

# echo "echo "APT::Default-Release \"stable\";" >> /etc/apt/apt.conf.d/70debconf

Add testing repositories to your sources list:

# echo "deb ftp://ftp.lt.debian.org/debian/ testing main non-free contrib" >> /etc/apt/sources.list
# echo "deb-src ftp://ftp.lt.debian.org/debian/ testing main non-free contrib" >> /etc/apt/sources.list

Alternatively you can use any testing mirror. Now all is left to do, is to install LXC itself:

# apt-get update && apt-get -t testing install lxc

Just to be sure your stable system does not “drift” into testing packages, you can remove the testing repositories from sources.list. As newer LXC package moves into stable, apt should automatically catch that and update accordingly without breaking any dependencies.

• Using lenny for the container:

For using lenny as a VM container simply install LXC tools from stable repository:

# apt-get update && apt-get install lxc

After isntalling LXC tools, it is time to set up cgroups:

# echo "cgroup /sys/fs/cgroup cgroup defaults 0 0" >> /etc/fstab
# mount cgroup

And a quick check to ensure everything is ok so far:

# lxc-checkconfig

In output you should see everything enabled apart “Cgroup memory controller”. If you want memory control via cgroups then the Kernel recompilation is needed, which is beyond the scope of this tutorial.

Creating your first VM

• Creating root filesystem:
  Create directory for VM and install Debian base system using lxc template:

  # mkdir -p /lxc/vm0
  # /usr/lib/lxc/templates/lxc-debian -p /lxc/vm0/

  This will take longer to complete only the first time you run it, as the subsequent template creations will use debootstrap’s cache.

  • Error “Failed getting release file”
    If you get this error during first install, simply change mirror in /usr/lib/lxc/templates/lxc-debian file and repeat steps, e.g.:

    MIRROR=${MIRROR:-ftp://ftp.lt.debian.org/debian/}

• Configuring VM:
  We are nearly done. The last step is to configure our VM container. Edit the file /lxc/vm0/config while taking special attention to parameters:

  lxc.network.ipv4 = 192.168.0.123/24
  lxc.network.hwaddr = 4a:59:43:49:79:bf
  lxc.network.link = br0
  lxc.network.type = veth
  lxc.network.veth.pair = veth_vm0

  Notes:

  1. IP (in lxc.network.ipv4) must end with CIDR notation of subnet. “/24″ means subnet mask of “255.255.255.0″
  2. MAC (in lxc.network.hwaddr) address must not be multicast
  3. Name of interface (in lxc.network.veth.pair) can be anything, but I prefer convention “veth_VM-NAME”

  Do not forget to configure VM’s interface in file /lxc/vm0/rootfs/etc/network/interfaces to something like:

  auto eth0
  iface eth0 inet static
          address 192.168.0.123
          netmask 255.255.255.0
          gateway 192.168.0.1

• Starting VM:
  Now the final step is to power on and start using your VM:

  lxc-start -n vm0 -f /lxc/vm0/config

  You will be attached to a VM console where you can login with user root:root. Do not forget to change the root’s password or disable the account altogether!

Other:

• Stopping VM:

lxc-stop -n vm0

• Attaching to VM’s console:

lxc-console -n vm0

• Auto-starting VMs when host starts:
  • LXC <0.7.5:
    Create config symlink:

    # ln -s /lxc/vm0/conf /etc/lxc/vm0.conf

    Then edit file /etc/default/lxc and include something like:

    RUN=yes
    CONF_DIR=/etc/lxc
    CONTAINERS="vm0"

  • LXC >=0.7.5:

    # ln -s /lxc/vm0/config /etc/lxc/auto/vm0.conf

• Cloning VM:
  This can be achieved by simply copying VM’s directory with:

  # cp -r /lxc/vm0 /lxc/new_vm

  After that do not forget to change /lxc/new_vm/config and /lxc/new_vm/rootfs/etc/network/interfaces files to reflect new changes of name, IP/MAC address and rootfs location.

• Sharing (binding) host’s directory in VM:
  In VM’s config include lxc.mount.entry, e.g. for VM running Apache:

  lxc.mount.entry = /var/www /lxc/vm0/rootfs/var/www none defaults,bind 0 0

References

1. http://wiki.debian.org/LXC
2. http://www.jotschi.de/?p=554
3. http://lxc.teegra.net/
4. http://nigel.mcnie.name/blog/a-five-minute-guide-to-linux-containers-for-debian#id3
5. http://jim.studt.net/depository/index.php/using-linux-containers-with-debian-lenny
   
6. http://alfie.ist.org/blog/2011/03/23
7. http...@lists.sourceforge.net/msg00783.html
8. http://ubuntuforums.org/showthread.php?t=1476832

Campus Party Europe: a special edition of what is considered the biggest event for technology, creativity and digital culture online in the world.

Intro:

I think this video says everything:

Invitation/Costs:

The invitation includes: the costs corresponding to travel to and from the event, accommodation (in the camping zone habilitated for the event) and maintenance. Yeah, I’m one lucky bastard ;]]

Updates:

You can follow official event feeds here:

• Youtube
• Facebook
• Twitter
• Flickr

P.S.

I’ll be updating (at least trying) every day’s impressions by new posts, and gallery dedicated to the CPE will be added, so stay tuned.

Content:

• UV box (THE box)
• Making board design
• Printing artwork
• Exposing unit to UV light
• Etching
• Source files

UV box:

Into word of home made  PCB’s I have stepped in with UV light.

• UV tubes: local store
• Sockets (G5): local store
• Box: local store

For starters I’ve scavenged “energy efficient fluorescence light bulbs” (the cheapest ones):

The pinout IMO is straight forward so no explaining here, unless you ask. Ok, the basic idea is to connect two grouped pins from the starter chip to one end of UV tube and other two grouped pins to the opposite end.

And actual box:

Board design:

Thirst thing you always have to do prior you have desired PCB is to design it! (captain obvious :-)) I always make my designs (or at least until now I have) with EAGLE. I do not consider myself expert, more like novice so for simplicity reasons I use hobbyist design rules (see files section). Almost always manual routing is needed, but hey, it’s better than nothing. I won’t explain how make board from schematics, IMO pretty good job is already done by instructables: Turn your EAGLE schematic into a PCB

Printing artwork:

You need to generate positive (as in copper track == black ink) artwork. It’s important to print in the best possible quality, because PCB quality depends directly on the artwork quality. The printed side should “touch” the copper when under UV light to avoid blurring. As for medium it’s recommended to use translucent material but as I have figured out default ordinary paper will do the job, just exposure time from 2-5 min. rises up for about 30-45 min. It’s not bad considering the rarity and cost of this type of paper.

Exposing to UV light:

After printing is done secure printed artwork tightly on the copper fiberglass board. Exposure time may vary from 2 to 45 min. it depends a lot on material being used, power of UV tubes, et cetera… For me it’s 30 min. Timer is essential for this kind of work to avoid over-exposure/under-exposure and in both cases quality of PCB decreases dramatically. You have to try yourself to determine the right values for your rig… If exposure time is right you should see yellowish tracks.

Notes:

• Don’t use glass to hold your artwork, use organic glass instead because normal glass stops about 90% of UV light
• DO NOT use short-wave UV lamps (like EPROM eraser tubes) – these emit short-wave UV which can cause eye and skin damage, and are not suitable for PCB exposure
• You have to remove the protective layer from copper to expose photoresist, try to do it in as little direct sun light as possible, the best time to do it is in evening/night.

Etching:

I’ve only used DP50 for positive photoresist development and it worked great. This stuff has many advantages over other solutions, most importantly is is very hard to over-develop. Even then it’s without dramatic quality decrease. Also it’s not temperature critical. Solution has a very long shelf-life so it’s great for home use (although,  I would not recommend to store chemicals at home). Available at my local store: dp50

For actual etching I use chemical B327 (Sodium persulfate (Na2S2O8)). Why B327 over others?

1. Clean – Does not damage clothing or dishes;
2. The solution is clear – you can see etching process;
3. Uniform distribution and dissolve rate

So this is second time when you have to experiment, but after you define times according you it’s all worth it.

That’s it, enjoy Your PCB ;-)

Files:

• EAGLE design rules: hobbyist.dru

Intro:

Up to now I have used only atmel AVR microcontrollers, so this bot is no exception with: ATmega16. Firmware is written entirely in C, also avrlib library for timing/PWM/UART was used. Although program is written with wxWidgets (C++) library, it won’t compile under Windows because the system calls in serial communication part, thought if you remove it, it should build with no hassle.

In action:

The build:

Basic communication scheme: (USB-to-RS232 (PL-2303))->MAX232->UART

Power: for servos and logic I’ve used L7805 with big heatsink (and yes, at operation time it was necessity) and DSA-20R-12 switching adapter

Servos: 2xMG995‘s for main arms and  for 2xHXT900 “claws”

uC: atmega16; 7.3728Mhz; LF: 3f, HF: de

Other thoughts:

In order to use make with firmware you should export avrlib directory with:

export AVRLIB=/path/to/avrlib

Color recognition would be nice, but because it’s easy to do (as in: no challenge) and some cross platform problems (Unix/Linux) with webCAM I didn’t implement it (also partly because it’s not intended for daily use, and You should know that programmers are lazy)

Any questions? ASK!

Source files (tl;dr):

• Firmware: rdrk_fimware.2009-09-11.zip
• CAD: cdr+dwg

Extra:

• video: rdrk.mov
• soundtrack: deep skydivers – momentum.mp3 (official site)

P.S. everything is under GNU GENERAL PUBLIC LICENSE.