Thanks for pointing that out Jeff. The way the usrp_packet_rx example works is with a multiply_const block just before the packet_rx (where the corr_est block lives) that by default is multiply by zero. So wouldn't we automatically get that /0?
Is divide by zero a common cause for flowgraphs to freeze? Is that what return code -15 is? Thanks, Cameron On Thu, Jul 2, 2020 at 4:07 PM Jeff Long <willco...@gmail.com> wrote: > If work() can reach this line: > > > https://github.com/gnuradio/gnuradio/blob/maint-3.8/gr-digital/lib/corr_est_cc_impl.cc#L311 > > with an all-zero signal, there could be a /0 error. > > On Thu, Jul 2, 2020 at 4:04 PM Cameron Matson <ncmatso...@gmail.com> > wrote: > >> Hi all, >> >> An update: I've noticed that when the flowgraph hangs it's usually >> because the correlation estimator block is outputting a relatively larger >> 'amp_est' tag (in my case this is normally a value < 1 but sometimes up to >> around 10. When it freezes it is usually > 50). If I then close the GUI >> tab the flowgraph doesn't actually finish until I hit the 'Kill' button in >> GRC. Only after that the terminal will print ">>>Done (return code -15)" >> I can't find anything on what that code might mean. Does anyone have any >> idea? >> >> Thanks, >> Cameron >> >> On Wed, Jul 1, 2020 at 5:31 PM Cameron Matson <ncmatso...@gmail.com> >> wrote: >> >>> Hi all, >>> I'm trying to send packet data from between two USRPs wirelessly using >>> the slightly modified uhd_packet_tx/rx examples (attached). It appears >>> that whenever the packet_rx block "finds" a correlation the entire flow >>> graph hangs. I say "find" because in order to get any output from the >>> correlation estimator block within packet_rx I have to set the threshold >>> very low, so I'm not very confident that it's finding what it needs. I've >>> tried playing around with the different encodings and header formats that >>> are part of the example, but it doesn't seem to change anything. >>> >>> First question: what could be causing the rx flowgraph to hang? I know >>> some of the downstream blocks in the packet_rx hier block use the tags the >>> correlation estimator outputs. >>> >>> Second question: what are some things I can try to improve the detection >>> in the first place? >>> >>> Thanks, >>> Cameron >>> >>
