[Battlemesh] FCC Contacts about Wifi Regulations

Paul Gardner-Stephen paul at servalproject.org
Fri Aug 5 04:27:09 CEST 2016


On Fri, Aug 5, 2016 at 10:53 AM, Juliusz Chroboczek <
jch at pps.univ-paris-diderot.fr> wrote:

> > So what we are planning to do is to have the power lead include several
> > additional pins, where the power cable indicates the regulatory regime
> > that applies to the unit, and also whether 3rd party firmware can be
> > loaded.
> If even the Serval project collaborates, then we are truly fucked.
> Has the FCC actually refused certification to hardware that allowed
> third-party images?  The mixed signals we are getting indicate either that
> the FCC realise that they have made a mistake and are looking for an
> honourable way out, or that the FCC is divided on the subject of
> third-party firmwares.

So our motivation is coming from a different direction than the FCC.
We need to be able to have Mesh Extenders imported into practically any
country at short notice, e.g., if we succeed in having the Red
Cross/Crescent movement adopt them.

The FCC is an easy player in this space, because we are only working on
900MHz and 2.4GHz ISM bands.

Where it gets complicated is if we have the <insert random small pacific,
african, european, south american, middle-eastern or other country here>
regulator and customs people want a rapid assurance that the devices cannot
be operated except on some band (which they might authorise for us at short
notice to meet a humanitarian need). (We are also negotiating with some
countries to ask them to open up the 915MHz ISM band, or some slice of it,
ahead of disasters, so that they can benefit, but that takes a lot of
effort per country, and success is not certain).

Also, it isn't economically possible for us to consider having stock of
versions for different regions/countries.  Just getting the IP66-rated
housing etc designed is stretching our little budget to the limits, but we
are determined to make a nice robust little product, that is strong enough
to be used in all sorts of horrible environments, such as tropical-maratime
and the rigours of the Australian Outback.

So we needed a way to have a single Mesh Extender Unit that can be used
anywhere, without having to open it (and potentially damage the IP66
seals).  We were also already forced from having a standard USB power
connector, partly by the IP66 requirements, but also because the new Mesh
Extender will accept 9V - 36V automotive power or a solar panel directly
(with the MPPT etc built into the Mesh Extender).  Similarly, we have a
2-cell LiFePO4 charge controller in there, so that you can just wire up two
cells, if they want it to work at night etc.

(We didn't put any batteries inside, because international freight of
lithium containing batteries is now a total pain in the butt, with DHL etc
charging an extra 90€ just to consider carrying a shipment of any size
containing any lithium batteries, even the LiFePO4 ones that you can shoot,
crush, feed to sharks etc, without them exploding or catching fire)

What we have done is to try to use common connectors, so that you can just
make your own cable if you need.  The ability to flash arbitrary firmware
will be via two options with the cable:

1. The serial console for the Ath9k module is routed via the cable to the
RFD900 UHF radio inside the unit.  Thus you can just break-out the serial
console, and use the bootloader to start TFTP booting a new image on. This
is probably how we will "factory" flash units.

2. If you ground a certain pin, it will tell the unit that it is allowed to
flash any firmware via other interfaces.

In other words, the only hardware restriction is you need the serial port,
which is the case on various other routers anyway, but we make the serial
port accessible on the outside of the unit.

> Please build a router that can be reflashed with third-party firmware
> without hardware modifications -- anything less, and you're unfaithful to
> your mission.  If you don't get certification, make a big fuss.

I think we are doing this, as described above, but please let me know if
you think that we are still barking up the wrong tree.

> (Something acceptable might be a web interface that only allows signed
> images, and a bootloader with a tftp server that allows third-party
> images.  Document in BOLD LETTERS that the tftp server is UNDOCUMENTED,
> that using it will VOID YOUR WARRANTY, that it will require RECERTIFYING,
> that using it might be ILLEGAL in your locale, and that it might cause
> As to using a non-standard power supply (or power cables) -- that's
> a horrible idea.  Power supplies get lost and power supplies get damaged.
> I am not buying any hardware unless the power supply is of a standard type
> that I can easily find at my local electronics shop.

(and also in reply to Mitar's comment along the same lines)

We are using DA-15 and DB-15 connectors for the power and utility (i.e. for
GPIO, and also to make USB charging ports if required) connectors, so that
people can chop up old PC joystick and VGA cables if they need to.  Since
the intention is that Mesh Extenders will often be running from solar(+
optional battery), there is already no "standard" connector that we could
be using.

We could, in theory, add a micro USB port as well, but given we already
need the other ports, this will increase the cost (since we need an IP66
USB connector), and probably also the size of the unit (its currently only
~10cm x 10xm).

Does this sound reasonable, or do you still have concerns, or ways that we
can improve this?

On a related note, does anyone have any experience with the Domino Core
board?  This is what we are planning to use as the Ath9k board.  Part of
our reasoning is we want 2 physical RJ45 connectors, but to use a 3rd
ethernet interface from the Ath9k board to connect to a (yet to be
designed) FPGA crypto accelerator board.

(Something else that we are doing is adding a bit-bashed microSD card
interface, and working to make the units so that they can have the power
cut at any time, without risking file system corruption while running
Serval, by making a simple copy-on-write Rhizome store that will use bare
SD card storage.  USB storage has proven to be totally evil in this role,
with USB memory sticks internal micro-controllers placing the sticks
permanently into a read-only "safe mode" when their internal memory
management data gets upset due to power being lost while it is being

Anyway, please keep up with the feedback, as it is extremely helpful.


> -- Juliusz
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> Battlemesh at ml.ninux.org
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