Re: [Discuss-gnuradio] USRP-FX2 interface / GPIF & FPGA f/ware / DDC specs

[Eric Blossom]

On Tue, Jul 04, 2006 at 07:53:51AM +0100, Kalen Watermeyer wrote:
> Hi again,
> 
> Finally managed to get my FX2 firmware onto my custom
> board. 
> 
> My intention is to mimic a reduced set of USRP
> functions on my custom board to allow me to use
> higher-level python modules to verify that my ADC's
> are working (a simple oscilloscope output for example)
> 
> Obviously, my FPGAs are different and will require
> custom firmware.
> 
> USRP-FX2 interface - As I understand it, all control
> calls to endpoint 0 are handled within the FX2 and do
> not require the involvement of the FPGA - is this
> correct? If not, then how do you setup the FPGA (once
> configured)? e.g. enable Rx or turning on debug LEDs

Yes, you understand correctly.

> GPIF / FPGA firmware - How many GPIF waveform
> configurations do you implement?

Two: fifoRd and fifoWr

> Also, when you configure your Altera I understand that this is done
> in a serial bit mode, is this embedded into the GPIF setup, or do
> you handle FPGA configuration explicitly using the 8051 core.

We bit bang the FPGA configuration from the 8051.

> Please could you point me to the correct FX2 source to
> determine your GPIF CTLx/RDYx lines and waveform
> decriptions, so that I can adjust code where necessary
> (my board will certainly have different pins tied
> between the FX2 GPIF lines and the FPGA)

All of these questions can be resolved by spending a few minutes with
the schematics and the code.  We used the Cypress GPIF designer (or
whatever it's called).  See gpif.gpf

> DDC specs - finally, in order to capture narrow-band
> data for processing by GnuRadio, I'll need to put a
> DDC in place. Please could you tell me an
> appropriate/realistic output bandwidth or complex
> sample rate that will work well with USB 2 and the
> Python graphical display modules.

We run at pretty much anything between 8MS/s complex and 250kS/s.

Eric