Re: [Discuss-gnuradio] Tx Path

[Brian Padalino]

On 4/13/07, Anmar Abdelaziz <address@hidden> wrote:
>  Hi,
>
>  I was looking at the UsrpTxModifications page in wiki, I want to understand
> how the Tx goes.
>
>  my question is what is the spi_bus that goes into the data block and come
> out of the command block, is it internal in the FPGA?

Currently the SPI and I2C busses are connected up to the FX2.  Those
diagrams are for the mblock specification for critical timing.

You can check out what I know from the FX2 here:
   http://gnuradio.org/trac/wiki/FX2

>  looking at the UsrpRfxDiagrams in the first digram I see the signal come
> out of the FPGA as I and Q,
>  But looking into the data sheet of the AD9862 there is only one input as
> the Tx data and from there it become as I and Q signals.

I am pretty sure the input to the AD9862 is interleaved I and Q data.

>  Is there any detailed diagram of the  'inside'  FPGA, I have know two
> different diagram one on the wiki page the other is writing by Oussama
> Sekkat( I have it as pdf), which one is the write one.

The current USRP without mblock modifications are correct from Oussama
Sekkat.  The ones that describe command and channel block FIFOs are
for mblock timing enhancements.

>  Another thing I want to send two signals from two tx boards but phase
> shifted from each other, is there a way to control the phase of the Tx
> signal?

I believe you may be able to send 2 real signals and control their
phases, but someone else here is a better authority on that than I am.

Brian