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Re: Synchronizing PPS pulse at specific moment

From: Marcus D. Leech
Subject: Re: Synchronizing PPS pulse at specific moment
Date: Mon, 22 Nov 2021 19:47:28 -0500
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.2.1

On 2021-11-22 17:37, isaac mario tupac davila wrote:
Hello everyone

My name is Isaac. I'm doing some probes of synchronization between two USRP's N200 and a trimble. What I'd like to do is the USRP's wait a specific time (3-5 seconds) before starting to send and receive data synchronize. So, I run my GRC flowgraph but I don't put the PPS pulse in the USRP's  for that "wait" time. But what I see is:

[32;1m[INFO] [UHD] [39;0mlinux; GNU C++ version 7.5.0; Boost_106501; UHD_3.14.0.HEAD-0-g6875d061
[32;1m[INFO] [USRP2] [39;0mOpening a USRP2/N-Series device...
[32;1m[INFO] [USRP2] [39;0mCurrent recv frame size: 1472 bytes
[32;1m[INFO] [USRP2] [39;0mCurrent send frame size: 1472 bytes
[33;1m[WARNING] [UHD] [39;0mUnable to set the thread priority. Performance may be negatively affected.
Please see the general application notes in the manual for instructions.
EnvironmentError: OSError: error in pthread_setschedparam
[32;1m[INFO] [MULTI_USRP] [39;0m    1) catch time transition at pps edge
Traceback (most recent call last):
  File "/home/soporte/Isaac/PruebaParaUSRP/TransmisiónUSRP/top_block.py", line 145, in <module>
  File "/home/soporte/Isaac/PruebaParaUSRP/TransmisiónUSRP/top_block.py", line 133, in main
    tb = top_block_cls()
  File "/home/soporte/Isaac/PruebaParaUSRP/TransmisiónUSRP/top_block.py", line 79, in __init__
  File "/usr/local/lib/python2.7/dist-packages/gnuradio/uhd/uhd_swig.py", line 4814, in set_time_unknown_pps
    return _uhd_swig.usrp_sink_sptr_set_time_unknown_pps(self, time_spec)
RuntimeError: RuntimeError: Board 0 may not be getting a PPS signal!
No PPS detected within the time interval.
See the application notes for your device.

It seems the UHD:USRP sink and UHD:USRP source have a short wait time for the PPS pulse.
¿ Is there a way to get a longer wait time for the PPS pulse in GNU Radio?....If it is not possible, any advice or idea to deal with it will be appreciated.

Isaac T.
Are both of these N210 in the same flow-graph, in a multi-Usrp object?

You might try "Next PPS" instead of "Unknown" PPS.

But you may still need to modify the code generated by GRC for this particular app, and it's unclear to me why you need to delay the PPS pulse.

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