RE: [Discuss-gnuradio] The ultimate SDR

[Ettus, Matt]

> Hence, my interest in integrating the digital down/up converter (I'm
> probably preaching to the choir).

I'm considering 2 different paths:

        - Digital upconverter, like you described
        - Direct-conversion

It depends how the LOs are done.  If there's a DDS used, then it makes sense
to go direct conversion.  Otherwise a digital up/downconverter is probably
necessary, since its hard to get fine tuning and very low phase noise out of
a conventional PLL.

> Me neither, but I'll do some checking around.  The usual 
> suspects include
> intel, SMCC.  The trick is to find one that *doesn't* have a PCI
> interface.

SMCC has one 10/100 chip without a PCI interface that I could find.  It
looks reasonable, and completely documented.  That's a big step from using
it though.
 
> > The other option is Firewire, but support under linux seems 
> sketchy, and I
> > have no experience with it.
> 
> I've also considered Firewire, but I too know nothing about it, other
> than that it's supposed to do 400Mb/sec and that none of my existing
> machines have it ;-)

The more I think about it, the more I realize that this is the perfect
application for Firewire (which actually has an isochronous mode!).
Unfortunately, I haven't been able to find enough info on available chips.
It may require a significant upper-layer stack in the device, and I doubt
one is available freely.

> We can of course fix the "sketchy support" problem.  Have you located
> any interesting Firewire MACs (or whatever they call them)?

The promising one I found from EMJ isn't cheap, but it looks pretty good:

http://www.emjembedded.com/products/ieee1394/starterkit.html

I haven't had too much time to look, though.  This looks like a good starter
page:

http://www.iol.unh.edu/training/1394.html

The opencores project, http://www.opencores.org/projects.shtml has cores for
10/100 Ethernet (listed as "completed"), and Firewire (not completed).  It
would be nice to use their ethernet interface, but it interfaces to the
Wishbone bus.  We might be able to strip that out, though.

Matt