Re: [Discuss-gnuradio] FX2 AUTO-OUT mode

[Eric Blossom]

On Mon, Jun 27, 2005 at 02:25:40PM -0500, David Carr wrote:
> Whats the trick to get the FX2 to work in auto-out mode?  I've tried
> with fx2_programmer's bulk_write command and with a modified version of
> the test_usrp_standard_tx code.  With fx2_programmer I get "connection
> to endpoint 2 timed out" and test_*_standard_tx sends 8MB before
> blocking indefinately.  Basically I think the FX2 just isn't taking any
> data in.  It seems that even if I don't have auto-out setup correctly, I
> should be able to at least write a few bytes to the endpoint...
> 
> Does anyone have anything that works that I can see?  Unfortunately the
> USRP firmware uses the GPIF mode instead of FIFO mode so I'm not sure
> how applicable the code is...
> 
> Thanks,
> David Carr

Hi David,

In my experience the FX2 docs are vague and/or wrong.  We use the FX2
in GPIF mode and in addition run in the extremely ill-documented "Flow
State" mode.   This allows us to burst data across the GPIF interface
at 96 MB/sec.  Some of the app notes are flat-out wrong.  When we were
doing the design, this seemed to be the only mode that would support
high bandwidth data in both directions.  I'm not sure if slave fifo
mode can run in both directions, but it's been a while since I looked.

I'm sorry I don't have any real suggestions for you.  It took Matt & me
something on the order of two months with a logic analyzer to get what
we've got working.

Eric