Thanks Wade and Marcus – I appreciate the insights and will make some tweaks on my end as a workaround.
Best, David From: Wade Fife <wade.f...@ettus.com> Sent: Wednesday, April 27, 2022 1:21 PM To: Marcus D. Leech <patchvonbr...@gmail.com> Cc: usrp-users@lists.ettus.com Subject: [USRP-users] Re: Programmatic determine rfnoc_chdr_clk from UHD? Hi David, I'm not super familiar with the software, but get_tick_rate() returning 0 might be because something's not implemented in the block controller software. You could look at some other blocks to see how that's handled (maybe the DDC/DUC). But I would expect get_tick_rate() to return the sample rate, which isn't the same as the rfnoc_chdr_clk rate. The way we typically track time in an RFNoC block is by counting samples. Each sample corresponds to one master clock tick (or a ratio of that if there's a DDC/DUC). We aren't usually very concerned with the absolute time, we usually care about the time to which a sample corresponds, which you can get from the timestamp in the packet and the sample count. If you need the absolute time, you can connect the radio time to your block. Just keep in mind that crossing the radio time to the rfnoc_chdr_clk requires a clock crossing, with special logic to handle that and a bit of added delay. The rfnoc_chdr_clk can drift relative to the master clock over time, so we don't usually use it for tracking time. There is a BUS_CLK_RATE register on the FPGA that has this information, but I don't see it exposed anywhere in the API. So, as it is now, it might be easier to just do a lookup based on the type of USRP. I don't know if there's an easy way to get to that register. Wade On Wed, Apr 27, 2022 at 9:57 AM Marcus D. Leech <patchvonbr...@gmail.com<mailto:patchvonbr...@gmail.com>> wrote: On 2022-04-27 09:53, David Raeman wrote: Hi all, Is it possible to programmatically determine the "rfnoc_chdr_clk" rate from a UHD application? More specifically, I have a custom RFNoC block clocked from rfnoc_chdr_clk, and I’d like to programmatically determine its clock rate from the associated custom software driver so I can convert tick rate to physical units of time. I know it varies by radio model [1], and I’d like the driver code to be portable across a few models. I’ve poked around quite a bit in the docs and code, and I haven’t found an obvious solution in UHD 4. I guess I could dump it into a register within my RFNoC block, but I wanted to make sure I’m not missing something in the existing framework. Calling get_tick_rate() on the block control object just returns 0. Thanks! David [1] https://kb.ettus.com/RFNoC_Frequently_Asked_Questions#What_are_the_clock_frequencies.3F _______________________________________________ USRP-users mailing list -- usrp-users@lists.ettus.com<mailto:usrp-users@lists.ettus.com> To unsubscribe send an email to usrp-users-le...@lists.ettus.com<mailto:usrp-users-le...@lists.ettus.com> Hmmm. The docs do suggest that "get_tick_rate()" on the *block* object should work, since it exists in the block base class. I'm not an RFNOC programmer, so just guessing... _______________________________________________ USRP-users mailing list -- usrp-users@lists.ettus.com<mailto:usrp-users@lists.ettus.com> To unsubscribe send an email to usrp-users-le...@lists.ettus.com<mailto:usrp-users-le...@lists.ettus.com>
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