[USRP-users] Sequence Errors on USRP N200

Jahshan Bhatti jabhatti91 at gmail.com
Sun Jun 24 20:06:45 EDT 2012

On Sun, Jun 24, 2012 at 6:08 PM, Josh Blum <josh at ettus.com> wrote:
> On tx, the timespec is converted to an absolute tick count. When the
> USRP gets a packet with a timestamp, it waits waits until that time in
> the packet matches its current time. All subsequent data is
> backpressured the timestamp'd packet in the front.
> Since N200 has a 100 MHz clock, the timespec can specify a clock cycle,
> which is on the order of 10 nanoseconds.
> -josh
> _______________________________________________
> USRP-users mailing list
> USRP-users at lists.ettus.com
> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com

Hmm. I've issued a stream command with a certain timestamp and as soon
as the rx data comes in, I send the data (with appropriate buffering).
The first packet of my tx burst has a timestamp that is some delay
later (10 ms, 100 ms, or 1000 ms). Yet I don't seem to get the delay
I'm expecting (which varies with different delays). As a test, I'm
delaying the GPS signal and feeding the authentic and delayed signal
into two timing receievers and monitoring the PPS. Is there some delay
inside the USRP that isn't accounted for?


More information about the USRP-users mailing list