Thanks EJ and Nick, I hadn't thought about the propagation of the streaming command occurring in UHD rather than on the FPGA. I was thinking that after issuing the rx_streaming start command to the downstream-most block in the chain, some magic was happening on the FPGA to get the upstream blocks started. However, I think this makes more sense that there is some magic happening in UHD such that the upstream blocks get the command to start streaming. I will let you know if I figure anything out. Rob
On Mon, Mar 25, 2019 at 12:37 PM Nick Foster <bistrom...@gmail.com> wrote: > I can tell you the answer to #3 off the top of my head: the two streams > will be sample-aligned, and if you use timed start commands, they will be > time-aligned. > > The other two are probably best answered by trying it out. Maybe someone > from Ettus can chime in. > > Nick > > On Fri, Mar 22, 2019 at 7:09 AM Rob Kossler via USRP-users < > usrp-users@lists.ettus.com> wrote: > >> Any suggestions? >> >> On Wed, Mar 20, 2019 at 9:49 PM Rob Kossler <rkoss...@nd.edu> wrote: >> >>> Yes, the example was for illustration only. You can throw a couple of >>> DDCs in between the radio and add/sub block to slow the rate down. But, >>> the questions are still the same. >>> >>> On Wed, Mar 20, 2019 at 7:49 PM Nick Foster <bistrom...@gmail.com> >>> wrote: >>> >>>> First things first. The flow graph you're describing don't work because >>>> the two radio blocks will saturate the bus going into the addsub block. You >>>> will need to decimate the streams going into the addsub block. >>>> >>>> I don't have a ready answer to your question about the streamers, but >>>> I'd suggest using timed commands to align the two radio streams, if UHD >>>> isn't smart enough to recognize the two radios and propagate the stream >>>> command accordingly. >>>> >>>> Nick >>>> >>>> On Thu, Mar 21, 2019, 6:46 AM Rob Kossler via USRP-users < >>>> usrp-users@lists.ettus.com> wrote: >>>> >>>>> Hi, >>>>> I am starting to develop more complicated RFNoC graphs and several >>>>> questions occurred to me. I am using my own C++ application with the UHD >>>>> RFNoC-enabled library. >>>>> >>>>> Consider a receive-only RFNoC graph with 2 radio blocks feeding a >>>>> 2-input, 2-output Add/Sub block. Also, assume there are two rx_streamers >>>>> connected to the 2 output ports of the Add/Sub block. Note that these >>>>> streams are no longer independent or one-to-one matched with the radio >>>>> channels. >>>>> >>>>> 1) How does an "issue_stream_cmd()" to one of the Add/Sub block ports >>>>> propagate back to the radio block? Actually, it would need to propagate >>>>> back to both Radio blocks no matter which rx_streamer I used since they >>>>> are >>>>> no longer independent streams. Does this make sense? >>>>> 2) What happens if I only call "issue_stream_cmd()" for one of the >>>>> rx_streamers instead of both? Perhaps since the other streamer isn't >>>>> running, it backpressures the streaming such that it eventually quits and >>>>> thus quits for the other port as well? >>>>> 3) Do I have to do anything in the Add/Sub block to sync up the >>>>> streams or can I rely on the first sample from Radio 0 being time-aligned >>>>> with the first sample from Radio 1 (assuming I issued timed start >>>>> commands)? >>>>> >>>>> Rob >>>>> _______________________________________________ >>>>> USRP-users mailing list >>>>> USRP-users@lists.ettus.com >>>>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >>>>> >>>> _______________________________________________ >> USRP-users mailing list >> USRP-users@lists.ettus.com >> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >> >
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