Re: [Discuss-gnuradio] external 1pps pulse

[Hans Glitsch]

> > I currently have four complex input signals coming in through USB
> > and I have a 1pps timing pulse coming from a gps source that I need
> > to synchronize the 64MHz clock to and also pass on to the PC so that
> > I know exactly which sample it occurred on.  Can someone give me
> > some guidance as to how I might accomplish this?
> >
> > Thank you,
> > Hans
>
> Hi Hans,
>
> In the good news / bad news department, the good news is that this
> shouldn't be hard to do with the "inband signaling" work that's
> currently underway.  The bad news is that this work probably won't
> be ready for a couple of months.
>
> In the interim, if you're willing to steal an LSB, you could modify
> the verilog such that it reported the presence or absence of the 1pps
> in the LSB of say, the I component of the first channel.
>
> Eric

Hi Eric,

Thanks for the reply.  I could use an LSB on one signal, although I hate to 
lose a whole bit when I only have 12 to start with.  I was hoping there 
might be a way to interleave another signal in with the four complex ones 
I'm receiving in the PC.  My data rate is fairly low, so another signal 
would not hurt much.   I haven't looked at the Verilog code yet.  Would a 
fifth interleaved signal even be implement in the context of the verilog 
code?  Also, what method would you use to receive the 1pps signal so the 
verilog code could stick it into an LSB, or another signal?

The other issue is synchronizing the 64MHz clock to the 1pps.  Is there any 
way to do this synch with the usrp's onboard clock, or will I have to make 
an external clock?

Thanks,
Hans