Re: [Discuss-gnuradio] AD9862 Functionality

[Eric Blossom]

On Mon, Feb 19, 2007 at 10:11:38AM -0500, Brian Padalino wrote:
> I am trying to figure out how the AD9862 MxFE is setup and I had a few
> questions for anyone who may be able to answer them.
> 
> RX
>  1. Is the internal DLL used to sample faster than 64MSPS?  If so,
> what is the DLL rate?  Is it possible this would ever want to be used?
>  2. Is the Hilbert Filter ever used?
> 
> TX
>  1. Is the Hilbert Filter ever used?
>  2. Is the NCO ever used?
>  3. Is the interpolation filter ever used?
>  4. Is the fixed [Fs/4,Fs/8] selectable mixer ever used?
>  5. Is the TX data ever sent as real-only instead of I/Q from the
> FPGA when it is actually a complex signal?
> 
> Aux
>  1. Are any of the auxiliary ADC/DACs used for AGC/VCO setting?
> 
> Thanks,
> Brian

Hi Brian,

> RX
>  1. Is the internal DLL used to sample faster than 64MSPS?  If so,
> what is the DLL rate?  Is it possible this would ever want to be used?

No.  IIRC the A/D won't run faster than 64MS/s.

>  2. Is the Hilbert Filter ever used?

No.

> TX
>  1. Is the Hilbert Filter ever used?

No.

>  2. Is the NCO ever used?

Yes, all the time (both coarse and fine)

>  3. Is the interpolation filter ever used?

Yes, always.

>  4. Is the fixed [Fs/4,Fs/8] selectable mixer ever used?

Yes.

>  5. Is the TX data ever sent as real-only instead of I/Q from the
> FPGA when it is actually a complex signal?

No, we always send I/Q to the 9862.  There are a couple of use cases
where you might want to send real data, but we don't implement them.

> Aux
>  1. Are any of the auxiliary ADC/DACs used for AGC/VCO setting?

Yes, all of them.  Details depend on the specific daughterboard.
The PLLs are controlled over SPI or I2C.


The code that sets up the AD9862's is contained in usrp_basic.cc and
usrp_standard.cc.  Most of it is in the constructors.

You may also want to take a look at the USRP motherboard schematic to
see how everything is wired together.  The aux DAC/ADC's are all run
to the daughterboards.

Eric