[hpsdr] The Basics (with updates)

[Bill Tracey]

Some answers and comments:

One caution on the Janus -- we've not validated operation at 192khz as 
yet.  We have validated 48khz and 96khz with good performance with the 
Xylo.    On at least one of the chips (PCM4202) we've looked at the 
datasheet implies performance at 192khz may not be good for our application 
as the noise floor seems to come up above 50 or 60 khz.

Another caution: at least with the Xylo and its FX2 firmware and device 
drivers,  96 khz will require Windows XP - the USB 2 stack on Windows 2000 
is just too slow to do the job.  The XP stack seems to be much better in 
this regard. on XP.

Janus -> Atlas->Xylo adapter board -> Xylo -> SDR1000   is probably the 
initial configuration we'll start with on getting the Janus up and qualified.

Then as Lionheart and/or Ozy come together we'll move over to them.   This 
will give us a lot more flexibility as we'll do our own  FX2 code and 
device dtriver to talk over the USB.    The FPGA used on the LionHeart 
and/or Ozy will be bigger and give us some more RAM bits meaning more FIFO 
space which will be welcomed in handling the higher audio data 
rates.   Also we'll get a 16 bit data path to the FX2 and USB bus from the 
FPGAs.

The Janus board is audio only (actually audio + PTT).  However, Janus + 
(Xylo | Lionheart | Ozy )  should be able to replace the parallel port 
connection for the SDR 1000.  At the moment we have PTT and CW keying 
running thru the Xylo.  Personally I want to hang an optical encoder off 
the FPGA and make my own knob.   It's a simple matter of programming 
(PowerSDR and FPGA) and a little bit of hardware glue (voltage level 
translation, or I2C bus adapter) to add a parallel port control connection 
to the SDR 1000 hardware to the FPGA board. However, I do not believe 
anyone has signed up to do the control connection work - don't think it's 
very high on the list of the current developers in terms of priorities.

1 pps gps timing should be doable on any of the FPGA boards.  Still have to 
do some hardware work on getting the 200 mhz reference clock out of the SDR 
1000.  May reevaluate the need for this once Flex puts out the stability 
upgrade to the 200 mhz VF oscillator.

Another configuration that may be of interest to some is to put a SoftRock 
style receiver on a prototype board and use that in place of the SDR 
1000.  Or take an IF tap off another radio, feed it to a Soft Rock and play 
radio that way.  Lots of possibilities and flexibility in the system.

Cheers,

Bill  (kd5tfd)

At 11:49 PM 5/2/2006, Alex wrote:
>***** High Performance Software Defined Radio Discussion List *****

<....>
INITIAL CONFIGURATIONS:

>ATLAS-LIONHEART/OZYMANDIAS-JANUS+SDR-1000
>     Would provide 192kHz operations with SDR-1000 via USB 2.0 interface 
> to a Windows/Linux computer
>
>ATLAS-LIONHEART/OZYMANDIAS-SASQUATCH-JANUS+SDR-1000
>     Would provide 192kHz operations with SDR-1000 standalone (no computer 
> required)
>
><...>
>Is JANUS interfacing to SDR-1000 just for I/Q signals or is it also 
>providing the LPT-based control interface?
>
>Are OZYMANDIAS, MERCURY and SASQUATCH going to use the Altera Cyclone II FPGA?
>
>
>Alex, N3NP



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