Forum: GNU Radio How to repeatedly & continously transmit a signal from a file ?

3a628fcdecc4782a28225b07500f23fe?d=identicon&s=25 Rickard Radio (Guest)
on 2013-06-04 19:06
(Received via mailing list)
Hi

- How is it possible to transmit a file (as a signal source) repeatedly
and continously without interrupts (with gnuradio & uhd) ??

Even without the USRP (i.e. just simulating with throttle & graphical
sinks and a file source) interrupts occurs (time-periods of no samples)
for each time the file repeats (i.e. starts over from the beginning).
Same thing with transmitting with USRP as uhd-source (then without
throttling of course), however no underruns are reported.

I want to continuously send a prepared signal from a file over and over
again but can't accept the interrupts each time the file ends & starts
over. This happens even at slow sample rates and I want to transmit
really fast!

I might have found a solution to this about year ago but now I can't
remember what I did something simple...
Somehow read in the whole file into cached memory so it doesn't need to
be re-read from disk for each repetition (in Linux) but how?

Rickard
0d057c642b38689bfa090206eec844b8?d=identicon&s=25 Monahan-Mitchell, Tim (Guest)
on 2013-06-04 19:11
(Received via mailing list)
> - How is it possible to transmit a file (as a signal source) repeatedly and
continously without interrupts (with gnuradio & uhd) ??

> Even without the USRP (i.e. just simulating with throttle & graphical sinks and
a file source) interrupts occurs (time-periods of no samples) for each time the
file repeats (i.e. starts over from the beginning). Same thing with transmitting
with USRP as uhd-source (then without throttling of course), however no 
underruns
are reported.

> I want to continuously send a prepared signal from a file over and over again
but can't accept the interrupts each time the file ends & starts over. This
happens even at slow sample rates and I want to transmit really fast!

> I might have found a solution to this about year ago but now I can't remember
what I did... something simple...
> Somehow read in the whole file into cached memory so it doesn't need to be
re-read from disk for each repetition (in Linux)... but how?

Maybe create a small ram-disk outside of GNU Radio, then copy your file
to it, then use the new path for the file source block?

- Tim
2474e637cd95190b38f78b5655f795e2?d=identicon&s=25 Sean Nowlan (Guest)
on 2013-06-04 20:01
(Received via mailing list)
On 06/04/2013 01:09 PM, Monahan-Mitchell, Tim wrote:
>> - How is it possible to transmit a file (as a signal source) repeatedly and
continously without interrupts (with gnuradio & uhd) ??
>
>> Even without the USRP (i.e. just simulating with throttle & graphical sinks and
a file source) interrupts occurs (time-periods of no samples) for each time the
file repeats (i.e. starts over from the beginning). Same thing with transmitting
with USRP as uhd-source (then without throttling of course), however no 
underruns
are reported.
>> I want to continuously send a prepared signal from a file over and over again
but can't accept the interrupts each time the file ends & starts over. This
happens even at slow sample rates and I want to transmit really fast!
>> I might have found a solution to this about year ago but now I can't remember
what I did... something simple...
>> Somehow read in the whole file into cached memory so it doesn't need to be
re-read from disk for each repetition (in Linux)... but how?
> Maybe create a small ram-disk outside of GNU Radio, then copy your file to it,
then use the new path for the file source block?
Depending how big this file is and how much memory you're willing to
consume, you can read your file into a vector (from Python, this is
pretty easy with numpy.fromfile() or a simple for loop ) and use it to
initialize a vector source (with repeat=True).
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