gr-ais with osmosdr

Nick Foster nick at ettus.com
Sun Aug 5 21:13:14 UTC 2012


On Sun, Aug 5, 2012 at 11:45 AM, Christian Gagneraud <chris at techworks.ie>wrote:

> Hi there,
>
> I saw a message in the July archive (I wasn't subscribed yet at that date)
> about updating gr-ais with osmosdr support.
> I was working on the same thing recently, so i decided to publish my fixes
> on top of Antoine's one.
> The result can be found here:
> https://github.com/chgans/gr-**ais <https://github.com/chgans/gr-ais>
>
> I got it working with both an FCD and an RTL:
> ais_rx.py --rate 96e3 --gain 30 --error -17 -d -D fcd=0
> ais_rx.py --rate 1024e3 --gain 30 --error -110 -d -D rtl=0
>

Thanks for doing this. I haven't been looking at gr-ais lately as I've been
doing gr-air-modes development in anticipation of our DefCon talk. Now that
that's over, I'll have some time to integrate these changes and hopefully
modernize a few things in gr-ais which I've been putting off.


>
> Strangely passing freq_err=XX parameter to the source (using -D), doesn't
> work, the use of --error is thus needed (which will do a set_freq_corr()).
>
> Antoine, if you want sample file, just let me know.
>
> Nick, are you willing to integrate these changing back in gr-ais, Apart
> from the added automatic decimation filter, the changes are not intrusive
> at all.
>

Yep, I'll pull it back in. I'm also going to need your help vetting the
changes against the FCD, as I don't have one. I do have an RTL dongle I can
do some testing with. Have you had much success with AIS on RTL?

--n



>
> The default settings for UHD are 256Khz sampling with decimation filter 4,
> with this change, the decimation is one when using FCD (96KHz fixed
> frequency) and 16 for RTL when used at 1.024MHz (this was the minimum
> working frequency for me).
> Or maybe would you prefer to allow the user to set it manually, and use
> this technique as a fall back only.
>
> Please let me know what you guys think.
>
> Thx,
> Chris
>
> --
> Christian Gagneraud,
> Embedded systems engineer.
> Techworks Marine
> 1 Harbour road
> Dun Laoghaire
> Co. Dublin
> Ireland
> Tel: + 353 (0) 1 236 5990
> Web: http://www.techworks.ie/
>
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