Behaviour of gs-osmosdr when multiple devices in the source

GNU Radio
1

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 L.
Principal Investigator
Shirleys Bay Radio Astronomy Consortium

2

On 10/23/2013 04:19 PM, Alexandru C. 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.

3

On Wed, Oct 23, 2013 at 9:58 PM, Marcus D. Leech [email protected]
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

4

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 L.
Principal Investigator
Shirleys Bay Radio Astronomy Consortium

5

On Wed, Oct 23, 2013 at 10:33 PM, Marcus D. Leech [email protected]
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