I tried the suggestion from Marcus and was
able to get the USRP1 to work with 4 real channels. I have a
simple GRC script which samples the USRP at 1MS/s and then
resamples the signal to 500kS/s and then writes to a file. I am
getting continuous Overruns with this GRC script on my laptop.
I have the same GRC script with the older GNURadio and when I
ran it again on the same laptop (I booted up a prior version of
ubuntu with an older gnuradio version that uses the USRP class
not UHD) it writes to file with no Overruns at all. I saw that
the custom quad channel USRP block has an fusb_block and
fusb_nblocks setting. These are both set to 512*32 but if I
lower them to something like 64*32 I start to see the Overruns.
Are there similar type settings I can adjust on the 3.6.2
version of GRC or GNURadio python scripts to get rid of the
overruns? I'm not sure if this is possible but I would like to
not have to boot into an older ubuntu version when I need 4 real
channels. The only thing that comes to mind is to adjust
noutput_items and I tried this but it didn't eliminate the
overruns.
Thank you, -Tom