I’m having some issues with the USRP and some latency in the output
signal. I am using a C++ program which modulates a signal and writes to
a file continuously.
When I use a normal file, the C++ program output looks perfect. When I
use a script made in GRC to read the C++ output file, the USRP generated
signal also looks perfect with an oscilloscope.
Now to get the process real-time, when I use mkfifo to tie the C++ and
GRC script together, I notice a problem. The C++ program constructs a
packet and then flushes and repeats continously. I’m sure this is less
than the 64KB buffer size with FIFOs. The GRC script reads from that
file and I see the signal output showing the modulated blocks, but I
notice it is not continuous and there seems to be 1-2 seconds of zero
signal, every 5 seconds or so.
I also see uU from the GRC script output about every 5 or so seconds.
Does anyone have any idea if this is a FIFO problem, or is it a USRP/GRC
issue? I am using a Duo core SU7300 laptop so I would think it should
run OK real-time unless the C++ and GRC script demand much more
processing power when used at the same time. Does anyone know any tricks
I can try?