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Re: [Discuss-gnuradio] USRP - FX2 / gpif / EEPROM / firmware questions

From: John Gilmore
Subject: Re: [Discuss-gnuradio] USRP - FX2 / gpif / EEPROM / firmware questions
Date: Wed, 10 May 2006 13:42:36 -0700

> I am developing a hardware project similar to the USRP
> in that it uses the 100-pin FX2 USB micro and houses
> several FPGAs (Xilinx in this case), as well as a dual
> ADC.

Great!  Any chance that we can use your hardware (or its design)?
There are lots of people doing things with GNU Radio who would be
happier to have more FPGA firepower.

How far along is your design?  How many will you be fabricating, and
are they going to be deep inside some other product, or is there a
chance that people will be able to buy them?

(If your hardware used the same daughterboard interface as the USRP --
both the electrical and mechanical specs -- then you could avoid *lots*
of RF section development.)

> appreciate a brief description of the fpga-fx2
> interface (control/data signals etc).

Matt and Eric have the details of how the USRP does it -- and how they
had to work around bugs in the FX2 (Cypress came up with a secret errata
sheet ONLY AFTER they beat their heads against the wall watching the
part do strange things).

But as an overview, the USRP's FPGA/FX2 interface is complicated
because it uses the GPIF mode, which supports bidirectional transfers
to/from the USB.  There is a much simpler "SSRP" design which just
supports unidirectional transfers (e.g. USB reads from the ADCs).
This uses the simple "slave FIFO" mode in the FX2, and also provides
slightly higher USB thruput, because the FX2 firmware doesn't need to
get involved in every block transferred.  See:


> Though I am trying to get this project up and running under windows,
> it may be simpler to try and integrate my firmware and so on within
> your software framework.

There's a very active Windows port of the whole GNU Radio software suite.



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