Something I’ve noticed over the years with the USRP is that it seems
unusually sensitive to power glitches, even tiny ones. Maybe
ground noise?
For example, removing an RF connector while the USRP is powered up can
sometimes cause it to go into “Protocol Error -71” in and
endless loop, and other things that might introduce small amounts of
ground noise.
This morning, my wife started the vacuum cleaner outside my office. The
USRP had been running entirely fine for 24 hours, and
then as soon as the vacuum cleaner started (causing a small AC
glitch), the USRP crashed with “Protocol Error -71”.
Is this an USRP thing, or is it that the USB is rather noise sensitive,
and you normally don’t see it because 99% of USB devices
are powered from the PC, rather than independently, as the USRP is.
Have other people seen this effect? I know at least one other person
who sees “sensitive USRP” issues, and I wonder if it’s
common.
–
Marcus L.
Principal Investigator, Shirleys Bay Radio Astronomy Consortium
Marcus L. wrote:
USRP had been running entirely fine for 24 hours, and
then as soon as the vacuum cleaner started (causing a small AC
glitch), the USRP crashed with “Protocol Error -71”.
I used to have problems when turning on a desk lamp or the computer
speakers. On Windows I was getting usb_reap_async errors.
Is this an USRP thing, or is it that the USB is rather noise sensitive,
and you normally don’t see it because 99% of USB devices
are powered from the PC, rather than independently, as the USRP is.
My problem went away when I upgraded my computer. This make me suspect
that
it is a USB problem.
– Don W.
I got a feeling of deja vu when reading your post. I haven’t had any
problems for a long time now, but I never really found the true cause
of these problems. Still, in my mind I have hypothetically correlated
the following with protocol and usb_reap_async errors:
- Loose power supply connector
- Bad USB cable
- Using a non-USRP under-rated power supply
- Old PC with a piece of shit USB controller
- Fiddling around with daughterboards while USRP is live
- Static electricity during the winter
But as I said, I haven’t seen these problems for a long time now. I
have managed to avoid causes 3, 4 and 5 during the last year or so,
but as I said, I don’t really know the exact cause for the errors as
they were fairly sporadic.
juha
On Sat, Apr 11, 2009 at 2:01 PM, Juha V. [email protected]
wrote:
- Bad USB cable
I’ve seen this as the reason for USB problems more than anything else,
typically using cables longer than the spec, or adding extenders, or
using cables not rated for 2.0. I hadn’t correlated it with power
issues, but I wouldn’t be surprised if there was some ground loop
issue resulting from having the USRP and PC powered from different AC
sources, and/or having different ground levels between the USRP USB
connector and the PC USB connector. In one case adding a USB 2.0 hub
in series fixed things.
Johnathan
Juha V. wrote:
- Static electricity during the winter
But as I said, I haven’t seen these problems for a long time now. I
have managed to avoid causes 3, 4 and 5 during the last year or so,
but as I said, I don’t really know the exact cause for the errors as
they were fairly sporadic.
juha
My power supply is more than adequate: 7.5V at 4A But I’ve seen this
with other power supplies as well (even the as-shipped one).
Many different USB cables over the years.
Modern PCs
I’d never fiddle with a daughtercard live!
Seen static problems, too. My usrp is inside a large aluminum chassis,
completed surround by ground (the chassis is grounded).
Still static is a problem sometimes.
The vacuum cleaner incident this morning gave me a strong correlation
event–USRP had been running just fine, and then
a little big of AC line “sag”, and USRP runs off to never never land.
When I had the system deployed at the SBRAC site, it ran for several
days without a hiccup. They have well-conditioned
power at that site, so that might explain the “longevity”.
My suspicion is that USB is more sensitive than you might expect to
ground noise, but that’s just wild speculation on my part.
–
Marcus L.
Principal Investigator, Shirleys Bay Radio Astronomy Consortium