On 19/11/2024 11:02, Tim Vancauwenbergh wrote:
Dear,
I am revisiting an issue I encountered earlier. I have a flow that
generates pulses with spaces between them continuously. To switch
between the RX and TX paths on a single antenna, I tried utilizing
GPIO to control an RF switch.
Tests were conducted on a B210 and X310. Initially, I used GPIO tags
on a USRP sink, but this caused continuous underruns. A sample rate of
4 MHz was used. I then switched to using bursts in combination with
ATR, but the issue persists. The USRP is unable to keep up, resulting
in significant underruns.
My goal is to send pulses at specific times and have the GPIO state
follow accordingly. When sending 0s or no samples, the GPIO state
should be low; otherwise, it should be high.
Could you advise on how to achieve this? I have attached my embedded
Python block code, which is positioned just before the USRP sink
block. This block adds the tags for the start and end of bursts and
handles the initial GPIO setup. For reference, I have also included
the manual GPIO control block.
Thank you for your assistance.
Best regards,
Tim Vancauwenbergh
Generally "U" underruns are caused by your *host computer* being unable
to "keep up" with the USRP, NOT the other
way around. The USRP internal performance is entirely deterministic.
If you program it to take in 4Msps, it will
be able to do that forever.
I'll note that Python blocks DO NOT PERFORM at the same performance
level as C++ blocks. By a significant margin.
I note that in one of your blocks, you're individually iterating
through samples looking for some kind of trigger.
This is guaranteed to have very poor performance characteristics, and
is unlikely to be able to "keep up" at anything
beyond perhaps 1Msps, but that will depend very much on your computer.
Also, (and I don't know if this is your issue), you can't schedule timed
buffers hugely in advance of when they will
actually get scheduled on the hardware--the hardware has very little
buffering.
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