[USRP-users] Streaming debugging in console window

Marcus Müller marcus.mueller at ettus.com
Tue Jul 28 08:37:18 EDT 2015

Hi Jason,

you're right, these are things printed by UHD:
"S"equence error (a packet was not received before the one that should 
come after it was received)
"U"nderrun (your PC didn't give the USRP the samples in time, so the 
USRP had no samples to trasmit)
"O"verrun (the USRP wanted to give you samples, but the buffers on your 
PC were full, so UHD had nowhere to put the new data).


Assuming this is on X3x0:
Now, unless you have a throttle in your GR flowgraph (never combine 
throttles and hardware!), your PC is too slow to keep up with the 
The "S" is especially worrysome, because it means that not only UHD's 
recv() and send() functions hadn't been called often enough to keep the 
realtime samples flowing, but either there was some packet reordering 
(we've only seen that on USB3-to-Gigabit Ethernet adapters and when 
routing UHD traffic through complex networks, and when NAT'ing the IP 
traffic in and out of a VM), or your OS was so busy executing software 
that it couldn't even receive an ethernet frame.

Best regards,

On 28.07.2015 14:27, Jason Matusiak via USRP-users wrote:
> Ultimately I think this is a UHD question, I am posting here instead of
> the GR list.
> While running some tests, I eventually see things like a bunch of U's or
> D's being spit out at the bottom of the GR console (I think I have seen
> an S before as well).  Is what these mean documented anywhere?  I
> couldn't seem to find it, but I think it is probably being reported by
> the UHD to GRC.
> _______________________________________________
> USRP-users mailing list
> USRP-users at lists.ettus.com
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