Re: [Discuss-gnuradio] Syncronising multiple USRP2 boards

[Tom Gross]

Marc (to answer your question about synchronizing 4 usrp2s, to the
whole list, not just a private message :-) ),

I guess you'll need that MIMO hub that is supposed to be in the works.

I imagine you saw this thread:

http://old.nabble.com/USRP2-questions-td19522195.html

the mimo "synchronization" we use with the cable, such as it is, works
with consumer off-the-shelf firmware.

I am however tinkering with the firmware and host software to try to
expose support for two receiver channels in the USRP2 largely so we
can avoid having to go with 4 synchronized USRP2s, which is I believe
the configuration that the genius who is designing this system, (not
me!), would like to do.  We haven't quite reached that point in our
development.


On Wed, Jan 27, 2010 at 10:57 AM, Tom Gross <address@hidden> wrote:
> actually with our configuration we simply synchronize using the MIMO
> cable and setting one of the USRP2s to slave its clock to whatever the
> other one is using (I forget exactly how this is done but we do pretty
> much everything with GRC, so I think it's just in the source block for
> the USRP2 - I am not at the location with our system at the moment so
> I can't give you a better answer).
>
> I'm pretty sure we are not using an external clock at all.  of course
> our configuration is specific to our application requirements - we use
> the second (slave) usrp2 to read a signal which is a function of the
> master's receive signal and its transmit signal (I am being
> deliberately vague).  I know that if I transmit from the master our
> system doesn't work (because I tried it).
>
> -Tom
>
>
> On Wed, Jan 27, 2010 at 9:21 AM, MarcW <address@hidden> wrote:
>>
>> I would like to synchronise multiple USRP2 boards together. I know I need a
>> 10Mhz reference clock and a synchronous 1PPS signal but have a few questions
>> regarding the specifics of this,
>>
>> 1.) The USRP2 FAQ suggests to use a GPS clock but has anybody managed to
>> successfully use anything else such as a function generator or other common
>> lab equipment?
>> 2.) Does the reference clock need to be a sine wave or can it be square
>> etc...?
>> 3.) What function should the PPS signal be?
>> 4.) Do I need to modify the FPGA firmware to enable locking from the
>> external signal?
>> 4.) Is an active splitter absolutely necessary to use or can i get by with
>> passive?
>> 5.) Is there a good way to test whether I have correct synchronisation?
>>
>> Marc.
>> --
>> View this message in context: 
>> http://old.nabble.com/Syncronising-multiple-USRP2-boards-tp27338003p27338003.html
>> Sent from the GnuRadio mailing list archive at Nabble.com.
>>
>>
>>
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