Forum: GNU Radio Behaviour of gs-osmosdr when multiple devices in the source

558c40b97bd1af8d912424757714bda9?d=identicon&s=25 Marcus D. Leech (Guest)
on 2013-10-23 21:59
(Received via mailing list)
I'm trying to understand the behaviour for gr-osmosdr when you have
multiple devices in the source -- does it start delivering samples
immediately,
   or is there a synchronization point, so that all devices start
delivering samples more-or-less at the same time?


--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org
68e4cb2871861bbe64d2eb3d42ca298e?d=identicon&s=25 Alexandru Csete (Guest)
on 2013-10-23 22:20
(Received via mailing list)
On Wed, Oct 23, 2013 at 9:58 PM, Marcus D. Leech <mleech@ripnet.com>
wrote:
> I'm trying to understand the behaviour for gr-osmosdr when you have multiple
> devices in the source -- does it start delivering samples immediately,
>   or is there a synchronization point, so that all devices start delivering
> samples more-or-less at the same time?

Hi Marcus,

I believe the behavior is different from source to source and
basically depends on whether the source block takes advantage of the
start/stop methods. For example, the Funcube Dongle Pro and Pro+
blocks are gnuradio audio source blocks that use the start and stop
methods and therefore will not start reading samples until the flow
graph is started. In other words, two funcube dongles will be more or
less synchronized, except for the clock differences. I think it is the
same for the UHD sources.

On the other hand, I have observed that if I create an rtlsdr source
block, after a few seconds it will start spitting OOOOOO out to the
terminal until I start the flow graph. This indicates that the rtlsdr
source is started as soon as it is created.

Alex
558c40b97bd1af8d912424757714bda9?d=identicon&s=25 Marcus D. Leech (Guest)
on 2013-10-23 22:35
(Received via mailing list)
On 10/23/2013 04:19 PM, Alexandru Csete wrote:
>
> On the other hand, I have observed that if I create an rtlsdr source
> block, after a few seconds it will start spitting OOOOOO out to the
> terminal until I start the flow graph. This indicates that the rtlsdr
> source is started as soon as it is created.
>
> Alex
Interesting.  I'll observe, out loud, that it would be useful for my
current coherence testing if the behaviour could be closer to "roughly
synchronized".
   Not sure how easy that is to do for RTLSDR.
68e4cb2871861bbe64d2eb3d42ca298e?d=identicon&s=25 Alexandru Csete (Guest)
on 2013-10-23 23:00
(Received via mailing list)
On Wed, Oct 23, 2013 at 10:33 PM, Marcus D. Leech <mleech@ripnet.com>
wrote:
>> less synchronized, except for the clock differences. I think it is the
> coherence testing if the behaviour could be closer to "roughly
> synchronized".
>   Not sure how easy that is to do for RTLSDR.

I think you can create one multi-channel source using 2 separate
devices. That may get you close. I haven't tried this feature though
so I don't know how it works.

Alex
558c40b97bd1af8d912424757714bda9?d=identicon&s=25 Marcus D. Leech (Guest)
on 2013-10-23 23:02
(Received via mailing list)
> Interesting.  I'll observe, out loud, that it would be useful for my current
> coherence testing if the behaviour could be closer to "roughly
> synchronized".
>    Not sure how easy that is to do for RTLSDR.
> I think you can create one multi-channel source using 2 separate
> devices. That may get you close. I haven't tried this feature though
> so I don't know how it works.
>
> Alex
>
That's the case I'm talking about...


--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org
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