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Re: [Paparazzi-devel] First power-up of Autopilot OK, some questions

From: David Carlson
Subject: Re: [Paparazzi-devel] First power-up of Autopilot OK, some questions
Date: Sun, 17 May 2009 23:18:25 +0300
User-agent: Thunderbird (X11/20090318)


I did test the modems, and they did work fine. I'm currently working on "stress testing" them to run into the 10% duty-cycle that people seem to be running into. So I know the modems work. As has been stated, it is very important to note that the 868 are not 5V tolerant, they need to be powered either with an adapter board or from the 3.3V bus (less desirable)

The USB board that comes with the 868s can be used as an "FTDI cable" to communicate directly with the board. I am going to sleep shortly, but can send instructions tomorrow if that is necessary.


Martin P wrote:
Tried again. Tried directly connecting the ground station adapter to the autopilot (pins 2 to 3 and 3 to 2 and connecting ground, pin 10 to 10): nothing. Same as trying with the modems. Made sure if the ground station adapter can work without a modem by locally connecting pin 2 to pin 3 and doing a loopback test in the xctu software. The messages window is empty. The strange thing: On the very first try, the ground station was populated and I saw the red/green flashing link indicator with increasing numbers. Ever since: nothing. The 868's were part of the "everything you need kit" by Cehbuzz. He wrote that he tried the modems and they work. Greetz, Martin
-------- Original-Nachricht --------
Datum: Fri, 15 May 2009 10:33:14 +0100
Von: Gareth Roberts <address@hidden>
An: address@hidden
Betreff: Re: [Paparazzi-devel] First power-up of Autopilot OK, some     

Sorry if I wasn't clear!

If the duty cycle is the problem, increasing the baud rate of either paparazzi or the modems will not help, at best it'll just stretch the time until they stop working to maybe 10 minutes. There is basically nothing you can do to fix this. The XBee needs to only transmit 10% of it's time. Paparazzi telemetry is a continuous stream of messages, and so it won't work with the 868's (unless you do something like resetting them every few minutes).

As for the 1mW thing, you are right, I talked to Digi live chat a while back and the chap definitely recommended that (said I'd get a few miles @ 1mW as well) until he found out I was trying to stream data, at which point he said it wouldn't work at all.

The idea about connecting the boards is very cunning, and should work (although you will need a common ground as well). I would recommend a serial cable though, I don't have an FTDI one, I use a Brainstem (though any 3V tolerant TTL level convertor will work), a power supply made from an LM78 and paperclips, a dodgy old USB->Serial adapter and a spare molex connector and some loose wires to connect to the paparazzi. Not that I'm on a budget or anything...If you are at a university or large org, it's exactly the kind of stuff someone will have in a cupboard somewhere.

As for the GCS view, if you are wondering whether it's your GCS or modem, go Tools -> Messages. If you get a tiny window you can't see, and it doesn't fill with tabs that flash green, you're problem is outside the computer.

As I said originally, I bought a pair of 868's, but they just don't work (at least not without the reset hack). Certainly while you are starting, try and get a set of XBee Pro 2.4GHz (they even play ok with video with some fiddling, I promise).


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