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

From: Cameron Lee
Subject: Re: [Paparazzi-devel] Support for multiple communication links
Date: Sun, 28 Oct 2012 17:38:38 -0600

That was the other thing I meant to ask about. I completely forgot to though.

We have a TWOG. It has two UART connections, but one is used for GPS. I figured that I could develop on it and test it while the GPS is not connected.

The Lisa M seems to have more UART connections though. If you use a PPM encoder instead of directly connected satellite receivers, does that give you two UART connections? Or not because they only have an Rx pin, not a Tx pin? Also, isn't there a way to get another UART from the last two PWM connections?

Whatever the case, for us, the primary use would be to have two links from the autopilot the the groups station but only one from the ground station to the autopilot. We can split the Tx of the TWOG in two and send one over 900 MHz and the other over WiFi.

Also, future hardware could have more UARTs for this, couldn't it?


On Oct 28, 2012 5:20 PM, "Chris Gough" <address@hidden> wrote:
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

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
> (
> 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
> _______________________________________________
> Paparazzi-devel mailing list
> address@hidden


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