[Commotion-dev] Android stick-PCs as a potential Commotion/FreedomBox/OpenWRT platform?

[Dan Staples]

The Android sticks certainly do make a tempting platform for some
experimentation. I wonder, however, how they compare in
capability-versus-price with the Raspberry Pi. An RPi by itself costs
US$35, and has ethernet, 2 usb, 512MB RAM, 700 MHz single core
processor, and draws b/w 500-1000 mA @ 5 V (= 2.5-5 W if my physics
degree serves me well ;) ). Attach to that a dual-antenna Atheros-based
USB wifi adapter (e.g.
http://www.tp-link.com/en/products/details/?model=TL-WN822N), which can
potentially do multiple virtual interfaces, one in ad-hoc and the other
in AP mode, and you got yourself a pretty capable gadget.

And at a recent conference, I powered some wifi-enabled, meshing RPis
with simple battery packs. I've even powered them from 2 D cells with a
proper voltage converter, which could potentially power a device for
more than a day.

Just another idea to throw into the mix...  I think experimenting with
the android sticks is a great idea.

cheers,
Dan


On 04/24/2013 05:28 PM, Paul Gardner-Stephen wrote:
> Hi all,
>
> Sorry if you have already thought about and discussed these devices,
> but they strike me as potentially very interesting for both
> communities, in addition to our own interest in them for the Serval
> Project.
>
> We have been looking at some of the cheap Android-based stick PCs as a
> possible platform for Serval Mesh Extenders, such as the MK802ii and
> more recent MK808B.  For more about the Mesh Extenders and their
> long-range UHF packet radios, refer to:
>
> http://developer.servalproject.org/dokuwiki/doku.php?id=content:meshhelper:main_page&#prototyping 
>
> or:
>
> http://servalpaul.blogspot.com/2013/02/building-serval-mesh-helper-device.html
>
> and subsequent posts to that blog.
>
> The newer generations of the Android stick-PCs have dual-core 1.5GHz
> ARM processors, 1GB of RAM and 16GB of flash, dual-antenna 802.11n
> Wi-Fi (although the firmware is not ideal, more on that later), USB
> host port, microSD slot, and HDMI out, all in a tiny thing about 80mm
> x 35mm x 15mm depending on the particular variant you get.  You get
> all that for under US$50, e.g., from geekbuying.com
> <http://geekbuying.com>.
>
> These typically come with a root-enabled ROM, and are very easy to
> flash with a complete new operating system.
>
> Thus compared with many wireless routers they have much greater CPU
> and memory resources, and similar or lower cost.
>
> What I wanted to discover what their power consumption was, because I
> want to run them off battery for really resilient deployments.  
>
> While I was initially concerned about the power consumption, I
> discovered that the later generation models can perform useful
> services, including running Wi-Fi for about 1W:
>
> http://servalpaul.blogspot.com/2013/04/comparing-energy-consumption-of.html
>
> The main issues that I have identified are likely to be:
>
> 1. The Wi-Fi antenna are little patch antenna, which probably don't
> have that great performance.  They could be replaced fairly easily
> though, I suspect.  On the up-side, they do have two antenna for doing
> clever 802.11n things.
>
> 2. The Wi-Fi firmware that comes with the ROMs I have found don't
> include simultaneous AP and ad-hoc capability, at least as far as I
> can tell.  This would need investigation.  They apparently use a
> Broadcom 8330 based Wi-Fi chipset in at least some variants, which
> leads to my next point.
>
> 3. The Wi-Fi chipset and design quality varies between suppliers of
> these, as it appears that they are all using a reference design of the
> RK3066 chipset, to which they add Wi-Fi.  Some use realtek or mediatek
> chipsets instead of broadcom.  Some implementations are better than
> others, e.g., some sub-optimal implementations seem to have a common
> ground-plane between the Wi-Fi and USB, which reduces the sensitivity
> of the Wi-Fi receiver. All this is both a negative and positive. On
> the negative side, some variants might be complete duds for our
> desired use-cases.  On the positive side, it might be possible to
> encourage one of these manufacturers to make one with, for example, an
> Atheros Wi-Fi chipset that is well supported by Linux, OpenWRT and
> Debian.  Related, I have yet to survey the complete OS image to see if
> there are any other closed binary blobs hiding around the place.
>
> 4. There is no on-board ethernet port on the cheaper models.  This
> could be solved with a USB ethernet adapter, or again, encouraging one
> of the manufacturers to make a variant that is better optimised for
> our communities needs.
>
> If anyone in the community is interested in working on porting OpenWRT
> and/or enabling simultaneous AP+ad-hoc Wi-Fi on these, we can probably
> arrange to provide a couple of MK808Bs to facilitate this.
>
> Paul.
>
>
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-- 
Dan Staples

Open Technology Institute
https://commotionwireless.net

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