[USRP-users] polyphase clock sync eats 100% cpu once it gets samples

Vladimir Rytikov kk6ygb at gmail.com
Tue Oct 3 06:54:18 EDT 2017


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.

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