Category Archives: Computers

Web Interface of the Dalek

So… controlling the Dalek over the web.

I decided that the target device was to be a Tesco HUDL2, so the layout was to fit on that size screen without scrolling.

It decided it would need a virtual key pad,  enough to give basic control and some spare buttons, and that I would need a feed from the camera.

So, a little bit of design fettling, image searching and pissing about, I came up with this control panel (caution: may include Dalek POV of beardy halfwit):

Obviously its not perfect (the wonky looking buttons are a design choice to reflect the general wonkiness of the whole thing though) and spaces have been left for other bits, but it will do for now.

I’ll put up the code behind it once i’m finished and happy with it (which might me another year or three). Ask me for it and I might send it you though…

Camera of the Dalek

I wanted to stream video from the Dalek camera to whatever browser was looking at it.  I asked t’Internet and it provided the answer.  Mr Miguel Grinberg has provided a nice tutorial on the matter, which I’ll now rip the bits I need from.

Install what you need and link header file.

$ apt-get install libjpeg8-dev imagemagick libv4l-dev
$ ln -s /usr/include/linux/videodev2.h /usr/include/linux/videodev.h

As an ex-Unix admin  who spent 10 years with a root prompt without anything going wrong, I fail to see the point of “sudo”. Just go to root and save the typing. You can be just as destructive either way.

Anyway, rant over.

Download, build and install  MJPG-Streamer

$ wget http://sourceforge.net/code-snapshots/svn/m/mj/mjpg-streamer/code/mjpg-streamer-code-182.zip
$ cd mjpg-streamer-code-182/mjpg-streamer
$ make mjpg_streamer input_file.so output_http.so $ sudo cp mjpg_streamer /usr/local/bin
$ sudo cp output_http.so input_file.so /usr/local/lib/
$ sudo cp -R www /usr/local/www

Thats it all done. To start it up, run the code snippet from rc.local below.

And to get the streaming running from boot time, you’ll need this is /etc/rc.local before the exit 0:

# start camera module for web server
mkdir /tmp/stream
/usr/bin/raspistill --nopreview -w 320 -h 240 -q 5 -o /tmp/stream/pic.jpg -tl 100 -t 9999999 -th 0:0:0 &
LD_LIBRARY_PATH=/usr/local/lib mjpg_streamer -i "input_file.so -f /tmp/stream -n pic.jpg" -o "output_http.so -w /usr/local/www" &

So far so good.  You can view the video streaming from your camera by pointing your browser thusly:

http://servername:8080/stream_simple.html

You will have to put the ip address of your pi in there if you haven’t fettled your DNS/hosts file to refer to it.

Next comes some hardware work on the case to get all the bits bolted/glued into place.

Ports of the Dalek

I’ve decided on what interfaces the Pi-Dalek will mounted on the rear of the case.

  • USB-B socket to accept power for charging the internal battery (a mobile phone emergency charger. Internally the socket offers a USB-A socket which is connected to the Pi with a short USB-A-to-microUSB-B cable, then the emergency charger, then another short USB-A-to-microUSB-B cable.
  • USB-A socket for memory sticks etc. Connected to the UTG socket with a short UTG cable.
  • HDMI socket. Connected to the miniHDMI socket on the Pi with a short adapter cable.

These will be mounted on the arse-end of the Dalek.  Two on the 3rd row up of the Dalek-bumps on the rear panel (both USB ports), with the HDMI socket on one of the rear flank quarters (3rd row up).

Ideally I’d like them all on the back, but the bumps on row 1 are blocked by the motor housing, while rows 2 and 4 have far too many structual bits behind it.

This still leaves me with the issue of mounting the camera. While I’d love to have the camera mounted to the eyestalk, this is impractical.  Mainly as the eyestalk is missing, but also because the camera module is a huge square blob that wouldn’t look right.

The best I can hope is to mount the camera on the Glacis, between the Whisk and Plunger, just above the top of the skirt. It will still mean that some cutting will have to be done, but it will probably not look as awful.

I’ve also decided that instead of mounting the Pi and Motozero directly to the base chassis, I’ll mount them upside down hanging from the internal ceiling at the top of the skirt. This shortens the distance to where I want the camera to be, and means only 6 wires need to be run down to the base (motor power +/-, motor left +/- and motor right +/-). Everything else will be skirt mounted. So the 40pin GPIO header connection twixt Pi and Motozero forms the split in the arrangement.

A sort of split between the head and body, if you want to make up some sort of analogy up.

I’m sure there’ll be some photos of it when its done.