Hi Vladimir, synchronization is usually among the most CPU-intense things a receiver does (only, if at all, contested by channel decoding for complex codes). So, the 100% CPU utilization don't sound totally unreasonable, depending on your system.
That being said, I don't want to rule out bugs, but for the time being, I'd declare this issue as "unclear, probably insufficient compute power". Can you tell us a bit about your computer, in terms of CPU model, motherboard chipset, RAM configuration, OS? If you install and run "htop"¹, you'll see which block does how much without much complication, and maybe also significant non-GNU Radio CPU usage (for example, my mail client and my browser idling use *serious* amounts of CPU). Another thing worth trying is to close all software that might be using CPU (check with htop!) and then run "volk_profile"; this should test a lot of hand-written implementations for certain math operations, which might significantly speed up the polyphase clock sync. Best regards, Marcus ¹: I'm assuming you're using windows; after starting htop, press F2 for setup, go into the "Display Options", enable "Show custom thread names", press Esc On 03.10.2017 12:54, Vladimir Rytikov via USRP-users wrote: > Hi, > > I am trying to run an example from GNU Radio - > examples/digital/packet/uhd_packet_rx and uhd_packet_tx with real USPR > radios connected via an attenuator and a coax cable. > > When I enable receiver by clicking on 'On' check box - the whole RX > flow graph freezes. > I think I manually adjusted transmit power and receive gain to be > within reasonable ranges. > > By disabling different blocks one at a time I found is that polyphase > clock sync inside packet_rx blocks kills the flow graph. It seems like > the signal is gaited by Correlation Estimator and once it gets the > correct sync word - the signal goes to Polyphase Clock Sync and CPU > dies - it is 100% loaded all the time. > > If I run only loop back simulation the whole flow graph seems working > fine. I wonder if noise or not very good signal destroys Polyphase > Clock Sync. > > I installed GNU Radio via PyBOMS - 3.7.12git* version. Please help to > find better idea on debugging it. > > with a different simple flow graphs Polyphase Clock Sync works fine > even when I feed noise to it and signal later. > > Thanks, > Vladimir > > > _______________________________________________ > USRP-users mailing list > USRP-users@lists.ettus.com > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
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