Thanks for the reply. Another thought I had on the topic was whether it would make sense for this info (sample rate) to be embedded in one of the metadata words of the streaming packets. And, not just this data but perhaps additional data such as the LO frequency and DSP frequency. With this information, the receiver would know which part of the RF spectrum was associated with the given baseband samples. But, I recognize that the metadata may be for more general advanced user purposes such that effectively reserving a few of these words for items like sample rate might be out-of-bounds. Rob
On Wed, Oct 8, 2025 at 5:23 AM Martin Braun <[email protected]> wrote: > Hey Rob, > > this is a great question. The short answer is: You don't have access to > the info, even though the Streamer is a node in the RFNoC graph. I believe > that would be a great API extension, but I would have to think about how to > cleanly integrate that without breaking any other APIs. > > You may have noticed we extended the streamers with the > post_input_action()/post_output_action() APIs that add RFNoC-features to > the streamers, and they don't do anything for non-RFNoC devices (like the > B2xx). Something like this may be the solution. But as of now, there's no > solution for you. > > --M > > On Fri, Sep 26, 2025 at 9:37 PM Rob Kossler via USRP-users < > [email protected]> wrote: > >> Hi, >> I have a custom c++ application that uses UHD to connect to RFNoC USRPs >> and tries to behave appropriately for arbitrary graphs. I'm most interested >> in directed graphs that go from the Rx radio to Rx streamers through some >> series of blocks including rate changing blocks such as DDC. I'm wondering >> if there is a generalized approach that would allow me to know the sample >> rate of the samples coming through a given streamer. >> >> Specifically, I just built an RFNoC image where the one Rx radio output >> was connected to a 1:2 SplitStream block and then to a 2-channel DDC which >> would allow me to downconvert 2 areas of the instantaneous spectrum from a >> single radio channel (e.g., GPS at 1176 and 1226 MHz). The DDC outputs >> then go to 2 Rx streamers. >> >> My understanding is that property propagation would cause the DDC to >> notify downstream blocks of the change to the EDGE property "samp_rate" or >> something like that. But, how can the UHD API user get access to this >> info. I realize that the rx_streamer is not actually an RFNoC block but it >> is conceptually similar in many ways. If I could call a function on the >> rx_streamer such as "get_input_rate()" (as I can using the DDC block >> controller), I would have a generic way to know the sample rate of the >> incoming stream. >> >> Let me know if there is some way to obtain this information from UHD. >> Thanks. >> Rob >> >> _______________________________________________ >> USRP-users mailing list -- [email protected] >> To unsubscribe send an email to [email protected] >> > _______________________________________________ > USRP-users mailing list -- [email protected] > To unsubscribe send an email to [email protected] >
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