Changing DB Modulation Frequency at run time

Hi all,

I am trying to find a way to efficiently modify the modulation frequency
of
the daughterboard oscillator at run time. I found where the a MISO_TX_DB
input variable is used in the FPGA code, but am not sure if this is what
I
am looking for or not. I am using the newest versions of UHD and GNU
Radio
with a USRP N210. I would like to create a Linear FM high frequency
signal.
I feel like there should be a fairly straight forward solution, but I
have
been researching for months and have not found anything. I found how it
was
done using the old USRP commands, but doing it with UHD seems to be much
more challenging. Basically all I want to do is modulate a square wave
at
some starting frequency that increases to an ending frequency over a
certain period of time. For example, it will change from 500 MHz to 900
MHz
over a period of one second.

Any guidance will help.

Thanks,

SDR at ONU Team