Part of the good news there is I'm utilizing the full 200 Msps clock speed so I've been skipping both duc on TX and ddc on RX, thus hopefully minimizing any front end delays to be measured
I'm slightly confused about the Rx metadata portion: I know in the uhd namespace there is the rx_metadata_t struct, but as far as I can tell, I as the user have been setting those values in the code in an effort to help synchronize both Tx and Rx. Are you saying this value I've been setting for time_spec will be the most accurate approximation of the first received sample (and when first sample was tx'd for that matter?) Thanks as always, Casey -----Original Message----- From: Marcus D Leech <patchvonbr...@gmail.com> Sent: Tuesday, July 6, 2021 5:25 PM To: Wolsieffer, Carl L. ERDC-RDE-CRL-NH CIV <carl.l.wolsief...@erdc.dren.mil> Cc: usrp-users <usrp-users@lists.ettus.com> Subject: Re: [USRP-users] UHD Transmit and Receive times The RX metadata includes time stamps. The time stamp clocks (and this event timing) will be as good as your common reference clock. There will be an inevitable latency due to the DSP group delay inherent in the DUC, which you will have to measure. It’s usually on the order of 10s of sample times but can vary from version to version of the FPgA code and sample rate settings. Sent from my iPhone > On Jul 6, 2021, at 5:16 PM, Wolsieffer, Carl L. ERDC-RDE-CRL-NH CIV via > USRP-users <usrp-users@lists.ettus.com> wrote: > > Hello, > > I am using two x310s both hosted from a common PC. I've stitched together a > few UHD examples to transmit a pre-recorded waveform from one x310 and > receive at the other at the exact same time. I'm using an FMCW waveform and > would like to run a correlation on the received signal to make an attempt at > measuring distance between the Tx and Rx. I used a common reference and PPS > between the two x310s and scheduled a transmit and receive by passing a > time_spec in the tx_metadata variable for the tx_stream->send() function as > well as the time_spec variable of the rx_stream->issue_stream_cmd function. > > My question is: how much stock do I put in these time_spec values? Is there > some timestamp I can retrieve that will tell me something closer to the truth > about when the first sample was emitted from the transmitter or was recorded > at the receiver? Or can I rely on the SDR adhering pretty strictly to the > time_spec value it was passed provided it was set sufficiently far in future > to give SDR time to schedule commands? > > > Thanks! > Casey > _______________________________________________ > USRP-users mailing list -- usrp-users@lists.ettus.com To unsubscribe > send an email to usrp-users-le...@lists.ettus.com _______________________________________________ USRP-users mailing list -- usrp-users@lists.ettus.com To unsubscribe send an email to usrp-users-le...@lists.ettus.com
