Re: [Discuss-gnuradio] Question on accessing ADC I/Q outputs on RFX2400 debug headers

[Eric Blossom]

On Tue, Apr 24, 2007 at 10:02:47AM -0400, Nikhil wrote:
> >Oops!  You've now smoked two RFX-2400 boards and/or the FPGA ;)
> 
> 
> Bzzzt!    Ok thanks.   Your explanation helped clear up my confusion about
> the RX and TX nets in the schematic and prevented frying my boards as well.
> ;)
> 
> >(I _believe_ that the high 7-bits are available for your use.  It mightbe
> 8, but I haven't looked at the >schematics in a _long_ time.  I'm notkidding
> when I say _you_ should check the schematics.)
> Yes it is only the 7 msbs.
> 
> >
> >If you can get by with a single RFX-2400, my suggestion is that you
> >put it on the A-side, and then put a Basic Tx and a Basic Rx on the
> >B-side.  Then you've got a total of 32 uncommitted i/o pins on the
> >B-side.
> 
> 
> 
> This is a good idea.  So if I insert one of each Basic Tx and Rx on side B,
> with the RFX2400 on side A, then the following should work (?)
> 
> u = usrp.source_c(0, 64)
>  u._write_oe(1, 0xffff, 0xffff)
>  u._write_fpga_reg(FR_DEBUG_EN, bmFR_DEBUG_EN_RX_B | bmFR_DEBUG_EN_TX_B)
> 
> and then in usrp_std.v
> master_control master_control
>     (....
>       //.debug_0(rx_a_a),.debug_1(ddc0_in_i),
>       .debug_0(rx_debugbus),.debug_1(ddc0_in_i),
>       .debug_2(rx_a_a),.debug_3(rx_b_a), .... );


Yes.  You may want to consider running a clock up there too,
since otherwise it's going to hard to figure out when you've got good
data.  You've got enough pins, since the data's only 12-bits wide.

Eric