I am using a USRP1 and an LFTX daughtercard and Ubuntu 12.04.
I am having an issue with a simple GRC script I made which has three blocks.
A WAV file source connects to a
resampler block and then to the UHD USRP sink.
When I run the script I get a single underun right at the start of running the script and no other underrun.
When I run the script using the sudo in front of it, I get two underruns right at the start of running the script and no other underrun.
I monitored the signal out of the
LFTX using an oscilloscope and noticed some blips/noise when the script is run and I believe they correspond to the underruns. I tried this with and without real-time scheduling enabled and didn't see any difference.
I tried the same exact type of script with an older version of GRC on a different laptop with Ubuntu 10.04. This uses the USRP sink block not the UHD sink block. This script plays the file perfectly without any underruns at all and I don't see the blips/noise at the beginning of the signal.
I am using the LFTX for an audio application and the blips/noise will cause a problem for me. Does anyone know why I am seeing this behavior with the newer UHD block? Is there anything I can do to eliminate it?
Many thanks, -Tom