Re: [Paparazzi-devel] Support for multiple communication links

[Chris Gough]

Hi Cameron,

If you going to add multiple serial modems directly to an existing
autopilot, you might need to find a way to free up some serial IO (i2c
GPS?).

We did this by cheating; inserting a linux computer between the
autopilot and modems. This was required because our ubiquity link
(bullet/rocket) is only accessible via ethernet, but it would allow an
arbitrary number of serial modems to be added (we use one or two).

It's not a very elegant solution though (or cheap, or light, or
compact), ethernet/usb connectors don't tolerate vibrations very well
so the whole thing requires a lot of hot glue to make it reliable.

Chris Gough


On Mon, Oct 29, 2012 at 6:58 AM, Cameron Lee <address@hidden> wrote:
> Hello everyone,
>
> I'm a fourth year Electrical Engineering student interested in working on an
> aspect of Paparazzi for a class of mine. I'm planning on adding support for
> multiple communication links at both the GCS and on the autopilot. Similar
> to item 6 in the wishlist
> (http://paparazzi.enac.fr/wiki/Software_Wish_List):
>
>
> The possibility to use multiple ground modem connected to a single ground
> station. The RSSI could be use to dynamically choose which currently has the
> best signal. This would allow the use of different antennas on each of the
> modems or have antenna pointing in different directions(?Possibly more
> hardware related)
>
>
>
> Here's a description I've written up:
>
> The goal is to improve the open source Paparazzi autopilot by adding support
> for multiple communication links to provide redundancy and increased
> flexibility. Currently, a single bi-directional serial data link enables the
> autopilot to provide telemetry to the ground station and the ground station
> to provide commands to the autopilot. This serial data link is usually
> created using RF radios and if it’s lost for any reason, all communication
> with the autopilot is lost. If two data links can be created, then
> communication can be maintained even if one of the links is lost. Typically,
> the two links would be of different varieties: two different frequencies, or
> a short-range high-throughput link and a long-range low-throughput link, or
> the same type of radio, but with different types of antennas, other
> combination.
> This project will involve enabling the autopilot and the ground station to
> each transmit their data through multiple links as well as receive data
> through multiple links. Receiving data through multiple links will involve
> deciding which link to take as correct based on the data coming in through
> all available links.
>
>
>
> Before I start working on this, I figured that I should ask for feedback -
> is this functionality indeed useful? Is this the best way to go about it? Is
> this project achievable (in particular on the autopilot side - will it take
> too much system resources)? Any tips or advice would be appreciated. Also,
> how difficult would it be to have different telemetry sent out over each
> link?
>
> Thanks,
>
> Cameron
>
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>



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