[USRP-users] X310 scheduled issue_stream_cmd()

Richard J. Muri ri28856 at mit.edu
Wed Jan 15 15:09:45 EST 2020


Sam,


Thank you for the help. Is there somewhere where the command queue depth is documented?


Also is the same command queue used for both commands scheduled from rx_streamer and those scheduled with set_start_time()?


Thank you,

Richard

________________________________
From: Sam Reiter <sam.reiter at ettus.com>
Sent: Wednesday, January 15, 2020 11:55 AM
To: Richard J. Muri
Cc: usrp-users at lists.ettus.com
Subject: Re: [USRP-users] X310 scheduled issue_stream_cmd()

Richard,

I believe what you're looking for is the depth of the command queue. For the X310, this FIFO has a depth of 16. Any command that you issue to the X310 that has a command time set will be held in this FIFO until the radio's time matches the command time, at which point the command is executed.

You should definitely keep track of the state of the command queue - overflowing this FIFO will put the radio in a bad state, usually requiring a restart.

https://files.ettus.com/manual/classuhd_1_1usrp_1_1multi__usrp.html#a191b78b00d051d3d51c2f719361c1fb5

https://files.ettus.com/manual/classuhd_1_1time__spec__t.html

Sam Reiter

On Tue, Jan 14, 2020 at 2:01 PM Richard Joseph Muri via USRP-users <usrp-users at lists.ettus.com<mailto:usrp-users at lists.ettus.com>> wrote:

Hello,


I'm using an X310 with a number of scheduled receives. I suspect there is a FIFO on the USRP that holds the stream_cmd_t until it is time to collect the requested samples. I have not been able to find documentation about the size of this FIFO. Could anybody point me in the proper direction?


Do I need to keep track of the number of stream_cmds in the FIFO? Is there some kind of acknowledge I can use to know the stream_cmd has left the FIFO? At the moment I am running an C++ application with two threads, one to issue_stream_cmd(), and one to recv(). I loop each operation, posting a semaphore after each recv() and waiting on a semaphore before every issue_stream_cmd().


I found this thread about using set_start_time():

http://lists.ettus.com/pipermail/usrp-users_lists.ettus.com/2016-July/049022.html


Are these commands on the same FIFO issue_stream_cmd() uses?


Thank you!

Richard Muri


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