[Commotion-dev] RPi & Commotion

[Dan Staples]

Moving this to the dev list, so other folks can benefit from the 
discussion :)

Hi Zach,

Currently, Raspberry Pi + Commotion is uncharted territory. What I did 
at the National Conference on Media Reform (NCMR) was simply use some 
RPis with wifi cards, put them in ad-hoc wireless mode, and then run 
OLSR to allow them to mesh multi-hop. I also had them running from 
battery packs I got from Radio Shack :)

Using the same wireless settings as the Commotion nodes (SSID, BSSID, 
channel, encryption), they were able to mesh with the Commotion network. 
However, they lacked the rest of the Commotion features. It is on our 
roadmap for the near future to add the rest of the features, and release 
a custom Commotion Raspbian image that you can put on an SD card and 
boot your RPi from.

As for wifi cards, I recommend any USB cards that use the ath9k_htc 
driver. My top choices for cards are:

1. TP-Link TL-WN821N (300 Mbps, MIMO)
2. TP-Link TL-WN822N (300 Mbps, high gain dual 3 dBi antennas)
3. TP-Link TL-WN722N (150 Mbps, with 4 dBi detachable antenna)
4. Ubiquiti WifiStation EXT (super powerful with 6 dBi detachable 
antenna, but much larger than the others)

I have only tested #1 with the RPi. I am worried about #4 working with 
the RPi, in terms of its power consumption. But in general, the 
ath9k_htc devices have great linux compatibility, and Ben West has done 
some great work getting them to do multiple virtual interfaces under 
OpenWRT. I hope to get this working under Debian as well.

The biggest challenge I foresee, besides running multiple virtual 
interfaces on a USB wifi card, is power. The RPi doesn't like to give 
more than 500 mA to USB peripherals, and wifi cards love to gobble up 
power! So stability can be an issue if the wifi card is drawing too much 
current...the RPi can start to act flaky or crash. I noticed stability 
issues at NCMR, but didn't have time to look into it.

Hope this is helpful...

-Dan

On Sun 21 Apr 2013 07:50:32 PM EDT, Zachary Menegakis wrote:
>
> Hi Dan,
>
> Good to meet you. I thought I'd follow-up on this email from Georgia.
>
> Would you be able to point us to any Raspberry Pi + Commotion projects?
>
> I've joined the distro lists and I'm interested in finding out some of
> the development challenges/pros/cons in this regard.
>
> Thanks,
> Zack
>
>
>
>
>
>
>
> On Tue, Apr 9, 2013 at 12:05 PM, Georgia Bullen
> <georgia at opentechinstitute.org <mailto:georgia at opentechinstitute.org>>
> wrote:
>
> Hey Dan!
>
> You mentioned in a recent thread that you got a RPi meshing with a
> network at NCMR. Bryan and Zack have been thinking about doing
> that too, so I just wanted to reconnect after the previous intro.
>
> Bryan was wondering what wifi cards and chip sets you use and in
> general I think want to stay in touch about RPis and Commotion.
>
> Bryan & Zack - are you on the Commotion-dev
> (https://lists.chambana.net/mailman/listinfo/commotion-dev) or
> Commotion-Discuss
> (https://lists.chambana.net/mailman/listinfo/commotion-discuss)
> lists? Maybe the three of you can chat about this on there?
>
> -Georgia
>
> -- 
> Georgia Bullen
> Field Operations Technologist, Open Technology Institute
> <http://oti.newamerica.net/>
> New America Foundation
>
>