Re: [Discuss-gnuradio] Multi-N210 synchronization issue

[Marcus D. Leech]

On 11/06/2011 03:12 PM, Khalid Jamil wrote:
> Thanks Marcus. So, it is the "select" block that is causing UHD device
> to reset every time.
>
> The reason I am using "Select" block is to avoid large file sizes, as
> the interested signals can occur any time for short periods of time. So,
> I have to run the program all the time, record a calibrating signal and
> then wait for experiment data to occur and record this to file sinks.
> Continuous recording can fill the hard disk very quickly; 1MS/s for
> eight channels, something like 32MB/s or 2GB/min.
>
> Any ideas on how can I record IQ data for discrete non-continuous
> intervals of time without causing the system to re-tune.
>
>
> Thanks,
>
> Khalid.
Actually, this is entirely independant of UHD and the devices it 
connects to.  The selector() must necessarily disconnect then reconnect, and
  this must necessarily create a phase hit.  Near as I can tell, the 
selector object (which is a synthetic object defined in GRC, but not, as far
  as I can tell, available anywhere else in Gnu Radio) will case a 
phase-hit regardless of what the source is.

If this were my problem to solve, I might use the "record" button to 
drive an adder which when you're not recording, adds some large
  out-of-range value to the output data, otherwise the data is in 
{-1.0,1.0}.  Then I'd dump my data over a FIFO, and use a C/C++ program
  to do "data slicing" on the resulting data, then use the data 
magnitude to decide if it's "real" or not.  That is but one approach.

You could dump your "record" variable to an external file, and have your 
recording program look for the value of that variable, and start
  recording when it sees the variable set to True (or 1, or oranges, or 
kobe-beef, or battleships, or whatever).

Another way is to simply have your file-sink write to "/dev/null" until 
it's time to write real data.  The filename can be changed dynamically
  and it "just works".




--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org