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] >
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