On 11/19/2018 06:35 AM, Fabian Schwartau via USRP-users wrote:
Anyone? This is a quite annoying bug and I am having trouble working
around it as I cannot meet my timing requirements.
I'm only about 50% certain that sample-rate setting is covered by timed
commands. I'll talk to R&D and get back to you on this.
Am 20.07.2018 um 11:05 schrieb Fabian Schwartau via USRP-users:
Hello everyone,
I am experencing some issues when switching the sample rate.
I have two synchronized USRP X310 with a total of 4 TwinRX. I am
doing timed commands to jump around in the spectrum with all
receivers at the same frequency (SIMO stuff).
I also need to switch sample rates in between. When I keep the sample
rate constant, everything works fine, but once I switch it between
two timed receptions, I get very strange errors. Like I get an
end-of-frame after just a part of the samples I requested.
It seems like it is not possible to time the sample rate switch
command. Here is a debug output of my code which makes it quite clear
what happens:
(1) Changed sample rate from 1e+07 to 5e+07
(2) Requested 32768 Samples
(3) Requested 32768 Samples
(4) Requested 32768 Samples
(5) Changed sample rate from 5e+07 to 1e+07
(6) Reading 32768 Samples
(7) Got only 6553 of 32768 samples at EOF
Commands 1-5 are transmitted to the USRP right away using its command
buffer. Then my program starts reading the first requested 32768 but
gets only 6553, which is precisely 1/5th of the requested samples. I
guess this is because he switched sample rate to 1/5th right before
executing the first stream command. But the sample rate switch is
also timed and should be executed after the three stream commands.
I attached the part of the code which is responsible for sending the
timed commands to the USRPs. This runs basically in a while(1) in a
seperate thread, while there is a seconds thread receiving the data
blocks, which produced the lines 6-7 of above output.
Is this a bug or feature I don't get? Are set_rx_rate commands not
timed when using set_command_time? How can I solve this isse? I need
very precise timing and also fast switching between frequencies and
sample rates.
Best regards,
Fabian
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