Hi,
I recently updated to GNU Radio 3.8 and noticed some code that receives 2
channels from a B210 is now always printing a single overflow (O) followed
by two drops (DD) right after the flowgraph starts. This happens regardless
of the sample rate and only when using 2 channels. It also doesn't happen
outside of GNU Radio; the UHD examples benchmark_rate and rx_multi_samples
never show overflows or drops. I've tested under macOS 10.14 and RHEL 7,
both with UHD 3.15. I also tried downgrading to GNU Radio to 3.7.13.5 and
problem goes away, so it seems like a GR issue and not UHD.
In debugging with a file meta sink I've found that the first header for
both channels always shows 38760 items before it gets a new tag. I did some
more testing with a very simple flowgraph of just a USRP source and null
sink. With 1 channel I can stream 20 MSPS without problems. With 2 channels
I tried rates 250 KSPS to 4 MSPS and saw the same behavior every time.
I thought that maybe the device was starting to stream before the flowgraph
was ready, so tried setting a start time several seconds in the future, but
that didn't make a difference. I also tried resetting the B210 and the host
USB subsystem.
Any idea what could be going on? A snippet of how the 2 channel B210 is set
up by GRC is below.
Thanks,
Michael
---
self.uhd_usrp_source_0 = uhd.usrp_source(
",".join(("", "")),
uhd.stream_args(
cpu_format="sc16",
args='',
channels=[0,1],
),
)
self.uhd_usrp_source_0.set_center_freq(1e9, 0)
self.uhd_usrp_source_0.set_gain(0, 0)
self.uhd_usrp_source_0.set_antenna('RX2', 0)
self.uhd_usrp_source_0.set_center_freq(0, 1)
self.uhd_usrp_source_0.set_gain(0, 1)
self.uhd_usrp_source_0.set_antenna('RX2', 1)
self.uhd_usrp_source_0.set_samp_rate(1e6)
self.uhd_usrp_source_0.set_time_unknown_pps(uhd.time_spec())
