Re: [Discuss-gnuradio] USRP2 PPS and REF

[Matt Ettus]

Suprin, Charles E. wrote:
> Doug,
>
> Working only on my single channel setup, what appears to happen is
> that there is the time stamp for the first sample in the frame. The
> frame alignment seems to remain a function of when the device was
> turned on.


NO.  Frame alignment is under explicit control from the host, as long as 
you do a "receive at" request.  That will allow you to specify EXACTLY 
when you want your samples.  If you do a "receive now" request, which is 
what you're doing, you'll get samples starting right away, which will be 
a function of host computer latency.

> Now if sync_every_pps worked with the 31 December 2008 firmware.  I
> think I need to wait for a newer FPGA/VHDL firmware release for that
> to happen.


Honestly, sync_every_pps is a hack and I don't know why you would want 
it.  It causes you to not know what second it is, since the clock is 
reset every second.

The normal "sync at next pps" makes more sense.  Since all the 
oscillators are locked, you only need to sync once, and everyone will 
remain in sync forever.

Matt