Re: [Discuss-gnuradio] USRP aux_dac

[Matt Ettus]

Angilberto Muniz Sb wrote:

> Hi All,
>
> Im working on a project that needs a continuos update
> of a slow varying DC signal. I was able to realize
> part of the project and put it into the FPGA. Now I
> need a way to update the AUX_DAC port on the 9862, but
> aparently that is handled by the USB uController ! Is
> that correct ? To set up the AUX_DAC do DO have to
> waste USB bandwidth?  (My intent was to use the PC
> just to download the FPGA image, do some setup and the
> USRP should run by itself...)
> Please shade some light...
>  

The USRP is wired such that only the FX2 can control the AD9862s. 

You can change this by adding R2001, R2004, and R2005 to the USRP.  All 
should be Zero-ohm resistors.  Be careful, because you will now have 
multiple drivers of these nets.  You'll need to have the FX2 STOP 
driving them before you make the FPGA drive them.

This will allow the FPGA to control the AD9862s.  You can also make the 
FPGA control the tuning of the RFX-series daughterboards.  Send me mail 
if you need that.

Matt