Questions regarding interpolator and usrp.sink_c configuration

Hi All,

Here I have a couple of questions during my project:

1, I am receiving “uU”(usrp underrun) when I am transmitting, it seems
that the data rate I feed to DAC is less than 128MS/s? I’ve already set
the maximum interpolation rate at 512. What’s the problem might be? I
guess the input data rate of usrp.sink_c is too low. If so, is there any
block plays the function of interpolator? If I have errors in my
reasoning or consumption, please point me out.

  1. Since the block : usrp.sink_c doesn’t have the parameter of Tx
    frequency in its parameter list. Is that means I have to define a
    function like set_freq() and call it? Is there anyway I could set a
    fixed tx frequency in python without input that from the command line
    option. I only have one daughterboard RFX2400.

Any suggestions and advice will be appreciated.