The actual code for setting frequency and gain (for daughterboard
dbs_rx) is found (in python!) in file
<source code of gnuradio>/gr-usrp/src/db_dbs_rx.py
(methods set_freq and set_gain). The procedure is quite abstruse and I
found no text document that would explain in a less terse format what
was done and why. I re-coded the process in C for a library to be
called from Ruby, but I have no certainty that the logic is
correct. If you want I can send you the code, but it has possibly less
documentation that the original python code (which is, I admit, quite
an achievement), and since I could not understand exactly what the
procedure was performing, I have no way to ascertain that my code is
correct.
Carlo