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Re: [Discuss-gnuradio] Synchronization issue with multiple USRPs

From: Khalid Jamil
Subject: Re: [Discuss-gnuradio] Synchronization issue with multiple USRPs
Date: Tue, 26 Apr 2011 21:22:00 +0300

Please correct me if I am wrong. I think that this random channel-channel phase offset at each acquisition depends on when each usrp 100MHz LO locks to 10MHz external frequency reference by PLL. How PPS will help in that case? Unless PPS is locked somehow to 10MHz clock?

Is there a good example to follow, may to start with 2 or 4 channels?

So grateful for your kind help.


On Tue, Apr 26, 2011 at 8:23 PM, Josh Blum <address@hidden> wrote:

On 04/26/2011 09:36 AM, Khalid Jamil wrote:
> The GRC file is attached. Here i am showing it scope sink with six
> channels.

The trouble is that you need to synchronize the time across all N
devices, and tell them to start streaming at a specified time.

So, if you want to synchronize N devices in GRC, every device needs to
all go into the same "uhd usrp" block; and specify the "sync unknown
pps" and "external reference" options.

Outside of GRC, if you wanted to use multiple device handles, you can
accomplish this by catching the pps edge and calling set_time_next_pps
for each handle.


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