[hpsdr] HERMES schedule question

[Ray Page]

Jeremy,

I thought about that. And will likely incorporate a Gig-E interface rather
than USB due to the time-line that I expect to have. I may be
misunderstanding something though. The Ozy-II will still be processing
baseband, right? In other words, the FPGA is processing the ADC samples to
create I/Q data that _then_ gets passed to the PC via USB, or Ethernet? The
raw data coming out of the ADC is 16 x 122.88 MHz, which translates to
1.966Gbps. So, unless some form of compression is used, I don't see how we
can get this down a Gig-E pipe.

Fiber-optic stuff always seems to have the WOW factor, but it is really
pretty simple once you get into it. Inside the FPGA, connections will be
made nearly identically to how they are now with the exception that the
connections are to the virtual parallel port versus the actual parallel port
of the ADC/DAC, etc. The cool thing is that all the virtual parallel
port/fiber-optic code already exist, it's time-tested, and I own it, so it's
available to us.

Gig-E can go 100m (and maybe this was your point in the first place), which
is well beyond USB, so the entire rig can live close to the base of the
antenna minimizing the advantage of fiber.  Hmmm... have to think about
that. It certainly eliminates the exposure to weather issue that an
antenna-mounted device would be subjected to. I'm sure the expense would be
lower as well. I can hear the air leaving my bubble.

-Ray

On Fri, Jun 18, 2010 at 5:08 PM, Jeremy McDermond <mcdermj at xenotropic.com>wrote:

> Wow --  That sounds like a very ambitious project, Ray.  I'm interested in
> what you come up with.  Keep in mind that software-wise, things are going to
> be moving towards a Gigabit Ethernet network interface (See the Ozy II
> Project) because USB can't handle enough of what we're sampling at the
> antenna.  So, given that in this case your data is going to get packetized
> at some point in time, it might be just as easy to get a fiber->copper Gig-E
> converter.  I'm not trying to discourage you in any way, but just trying to
> let you know that the USB on Hermes is about to be eclipsed by Ozy II to a
> certain extent.
>
>
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