synchronize

[jansel086]

Hello,

I am trying to synchronize two USRP 2940Rs and phase align their LOs for transmission.  We would calibrate the phase However, we have encountered the problem where one of the channels would have a 180 degree phase shift when we would rerun the VI.  The channel with a 180 degree phase shift is random and can't be predicted. 

I thought the SBX boards does not have the 180 degree phase ambiguity.  Is there something that we are missing?

[Sarah_Y]

Hey jansel086,

Do you have a 2940R or a 2942R?  The 2940R has WBXs and the 2942R has SBXs inside.  If you have the 2940, this is expected behavior for the WBX.

[jansel086]

Hi we have the USRP 2942Rs. 

I was reading that the process for synchronizing 294x/295x are different in comparison to the 292x/293x.

294x/295x

http://zone.ni.com/reference/en-XX/help/373380D-01/usrphelp/synchronization/

292x/293x

http://zone.ni.com/reference/en-XX/help/373380D-01/usrphelp/mimo_sync/

We are currently applying our method using the 292x/293x examples for 2942r.  The blocks used for the 294x/295x appears to be in the communication toolbox which we don't have.  Could that be the reason?

Also, will I be able to load an FPGA firmware that allows me to use the 2942r in Ubuntu and be able to revert back to the NI fpga image? 

- Jan

[Sarah_Y]

Hey Jan,

There are 2 different driver APIs for the 294x/295x.  You can either use the host based NI-USRP API with LabVIEW, or you can use LabVIEW FPGA and our instrument design library (IDL).  The link you posted for synchronizing the 294x/5x is specific to the LabVIEW FPGA IDL.  If you are using the host based NI-USRP API, the same software sync technique can be used for the 294x/5x as you previously used for the 292x/3x.  The hardware set up might be a bit different, the 294x/5x does not have a MIMO connector.  To sync multiple 294x/5x units, you will need to provide a shared 10 MHz reference clock and a shared PPS clock.

I think I already answered this on another post you made, but yes, you can go back and forth between different FPGA images to use your 294x/5x with LabVIEW and UHD.