[hpsdr] HERMES schedule question

Fri Jun 18 18:55:19 PDT 2010

Hi Ray,

You are quite correct. The receiver board (Mercury) incorporates a Digital Down Converter that takes the 1.966Gbps ADC data at 16 bits per sample and reduces it to 48/96/192ksps at 24 bits per sample.  This slower data is passed over the Atlas bus to either an Ozy board (USB interface to the PC) or shortly an OzyII  board (Gigabit Ethernet).

Hermes does the same except the functions of Mercury and Ozy are combined on the one board.

73's Phil...VK6APH 
  ----- Original Message ----- 
  From: Ray Page 
  To: Jeremy McDermond 
  Cc: hpsdr at openhpsdr.org 
  Sent: Saturday, June 19, 2010 6:37 AM
  Subject: Re: [hpsdr] HERMES schedule question

  ***** High Performance Software Defined Radio Discussion List *****

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  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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