Re: [Discuss-gnuradio] zero crossing detection. parallel inputs to USRP

[Eric Blossom]

On Mon, Aug 09, 2010 at 04:42:58AM -0700, Phong Do wrote:
> 
> Hello,
> 
> I have once post this message. Please help me cause its very urgent. 

Generally when there's no response, it's an indication that the way
you asked your questions failed to attract the attention of people who could 
help.
Try following the suggestions in here:

  http://gnuradio.org/redmine/wiki/gnuradio/ReportingErrors
  
> I now have a project with the following specifications:
> I need to send 2 input-signals parallel over USRP, then find out the
> zero-crossings (time) of each signal so I can calculate the phase difference
> of them.
> The 1st signal S1 is up to 1MHz
> The 2st signal S2 is about 50 Hz
> 
> 1. Sending 2 input signals parallel to USRP:
>    My idea is:
>    - Sending these 2 Signals in 2 separate daughter-boards LFRX

That could work.

>    - (Or) Put them two on only one LFRX through the 2 SMA connectors. 

That could work too.

>    - How about using digital I/O pins ?

Not recommended.

>    - What is the maximum voltage can I feed the daughter-board through SMA ?

I'm not sure.

>    - Will the inputs be synchronously sent and sampled ?

Yes.

> 2. Zero-crossings detection: 
>    - How can I find out the zero-crossing time, esp. of the signal S2 ? 

What have you tried so far?

Eric