How to synchronized the Tx and Rx

[yh10915]

Hi all,

I am trying to build a radar system in LabVIEW Communication, so I need to synchronized the Tx and Rx in one USRP 2900. I have already build a synchronization system (attached below), and both the "Reference Frequency Source" and "Timebase Clock Source" were set to "internal" ,but the error "niUSRP Initiate.gvi<ERR>A stream command was issued in the past" was shown and it could not turn on the Rx. Does anyone  know how to solve this problem?

Best regards.

Thanks

Olivia

[mferguss · Accepted solution]

Hi yh10915,

I have come across an error code, I believe this could potentially be the source of your issue:

Error -107411864 "A stream command was issued in the past" occurs when you set Timebase Clock Source to PpsIn and do not provide a timebase clock source to the PPS IN port.
If you set Timebase Clock Source to PpsIn and do not provide a timebase clock source to PPS IN, the USRP device will revert back to its internal timebase clock source. This may result in error -1074118649 "A stream command was issued in the past."

Workaround: Provide a timebase clock source to the PPS IN port.

Kind regards, 

Matthew Fergusson

Applications Engineering 

National Instruments

[yh10915]

Hi Matthew Fergusson,

Thanks for your reply.

I used dual function generator to output same PPSin and REFin into two USRP. And it works very well in Labview, but when I try to run it in Labview Communication, the error of 'A stream command was issued in the past' was shown.

Best regards.

Olivia