Re: [Discuss-gnuradio] Re: "Open-Hardware"

[Marcus D. Leech]

> schrieb Marcus D. Leech on 2011-01-12 01:44:
> You just ad a second interface that is HID, which is available on every
> platform and easy to handle. That's how all the soundcard-like DDS do it.
Ah, yes of course.

> The only problem is that Microsoft promised in 2005 to implement UAC2,
> but "forgot" to do it until now. BTW they have a big mess with USB, as
> Daniel Mack, Linux UAC2 author wrote: "Inevery cruel reincarnation of
> their OS, it has different issues." I spare you the terrible details an
> leave out the rest of his summary.
Well, I *personally* don't care very much about random-disk-noise, errr, 
I mean Windows,
  but I'm sure others do :-)

> I read the UAC1 specs a year ago and thought "Great, you can advertise
> up to 4MSPS on USB Audio!", but it turned out that it was specified for
> USB 1.1, which just cannot handle the data rates. :-( Then I found the
> SDR Widget, and they really get everything out of the Windows UAC1 driver.
I thought you couldn't do more than 48Ksps with UAC1, no way no how.
  Perhaps I should read that spec again, but it seems that UAC2 is the
  way forward, with 384Ksps audiophile DACs using UAC2 already becoming
  available.

An interesting device is the AD6655, which is an integrated ADC and
  signal processing chain (complex DDC, and one or more CIC decimators
  and FIR filters).  It can produce 4 discrete output channels, but the
  "cool" thing is the built-in DDC+etc chain.  Doing the BOM math, going
  with something like the AD6655 then straight into the FX2 would be 
cheaper
  than somewhat-cheaper-highspeed-ADC+FPGA+FX2.

The AD6655 is designed as an (non-zero) IF sampler, and I haven't read 
enough of the
  datasheet to determine if it can do simultaneous sampled I/Q with a 
quadrature D-C
  front-end in front of it. It *does* have two ADCs, but they're 
intended for diversity
  reception, rather than quadrature sampling--it has its own quadrature 
converter
  inside it.

--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org