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Re: [Xylo-SDR] Saxo



Edson,

Thanks - understood. As Bill points out, at the moment our focus is just to get something working using the drivers that come with the Xylo board. That is real close now. I have full duplex going at 48k 16 bit and Bill will soon have his "Hello World" ( I/Q from an FPGA test signal giving a carrier on the PowerSDR bandscope).

I am already facing issues with the Bulk USB mode in that if the PC gets too busy then, although the packets arrive, they may be too late to be of use. So far I've been able to code round that in VHDL by adding Tx and Rx FIFO's in the FPGA.

We will need to face these issues shortly and they way you suggest may be the way to go - not an area I've any experience in and at the moment the coding load is between Bill and myself.

As Bill has already requested, if someone would like to help with USB/FX2/Drivers then jump straight in - we are more than happy to junk all our code if it leads to a better solution.


73's  Phil... VK6APH


----- Original Message ----- From: "Edson Pereira" <ewp_jp@ybb.ne.jp>
To: "Xylo-SDR Discussion" <xylo-sdr@lists.ae5k.us>
Sent: Monday, January 23, 2006 6:40 PM
Subject: Re: [Xylo-SDR] Saxo



Phil,

The USB audio stream could be handled using the USB Audio Class
specification. The other functions could all be implemented using the
USB HID specs. Both device drivers are included with all modern OSes.
The nice thing is that a good amount of though has gone in the
implementation of the USB Audio spec specially regarding low latency.
The specs for the USB HID is quite extensible and a lot of things can be
done. Most USB gadgets that do not need low latency high speed transfers
use the HID specs. USB keyboard, mice, etc. are all USB HID. One other
very important advange I also see is that both specs are well
established standards.

73,

-- Edson

pvharman@arach.net.au wrote:

Chris,

I don't think that a generic USB Audio device driver will do what we want.
Apart from full duplex audio our USB link will take  PTT, CW keyer,
Forward/Reverse power, SWR, 200MHz frequency error, LPF filter settings, BPF
filter settings, DDS/NCO frequency etc etc.

I have zero knowledge of PC drivers so I may be completely wrong about this.

Phil...VK6APH






Quoting "Christopher T. Day" <CTDay@lbl.gov>:



I would like to reemphasize a point in my original comment and which
Edison alluded to: If out USB device follows the USB Audio Device spec,
then the required driver is GENERIC, i.e., it is written and supplied by
the OS supplier, not us. [Emphasis mine and likely wrong since I haven't
really read the spec yet, but it sounds like this is the way it should
be.] Like wise for at least some of the other USB Device Classes. As
evidence, as faar as I can tell, I'm running my SDR-1000 with a Sound
Blaster MP3+ USB device and using the generic MS USB Audio Device
driver, not the one from CreativeLabs.


Chris


-----Original Message-----
From: Edson Pereira [mailto:ewp_jp@ybb.ne.jp]
Sent: Saturday, January 21, 2006 9:32 PM
To: Xylo-SDR Discussion
Subject: Re: [Xylo-SDR] Saxo


Hi Phil,

Thanks for the comments.

In order to avoid the problems caused by non-synchronized clocks, I am
considering resampling the PC soundcard audio input and output (which
will be running at a lower sampling rate) using a fractional FIR
decimator and interpolator. I still need to look closer at the problem
and see how easy or complex it is.

One reason I have purchased the Saxo is that I could use 2 ADs and 2 DAs
and avoid all the problems you have mentioned. However, VHDL or Verilog
are obstacles for me at the moment. Verilog looks a bit familiar due to
its C-like syntax, but I need to dedicate some time (the most scarce
resource at the moment) to learn it enough to be able to do something
useful.

73,

-- Edson


Phil Harman wrote:



Hi Edson,

Your project sounds very interesting. Just one thing to be aware of.
If you use an external A/D converter as input and a sound card for
output then unless the crystal clocks are exactly the same frequency
you end up getting breaks in the audio due to the beat between the two


clocks.


For example, using my Wolfson A/D as the source and my Delta 44 to play


back all is well for about  a minute - the clocks have then drifted
apart enough to cause a frequent ticking sound.

This is not a problem for our project since all the A/D's and D/A's all


run off the same master clock.

This was the reason that until the dual sound card Delta 44 we did not
have VOX on the SDR1000.

There may be a way round this problem - if you find one be sure to let
us know since using the internal PC for playback would be a nice


option!


73's  Phil... VK6APH
]
----- Original Message -----
From: "Edson Pereira" <ewp_jp@ybb.ne.jp>
To: "Xylo-SDR Discussion" <xylo-sdr@lists.ae5k.us>
Sent: Sunday, January 22, 2006 12:41 PM
Subject: Re: [Xylo-SDR] Saxo






Hi Chris and Phil,

I would like to implement a USB Audio device exactly in order to avoid


having to write any device driver software on the PC side. The USB
Audio Class device specification should not be too complex to
implement in the
FX2 (I hope). I have recently acquired the TUSB3200 chip, which is an
embedded USB Audio stream controller. It does however only support USB


full speed (12 Mbps), which will limit the sampling rate to 96 kHz
half-duplex. This is ok for me at the moment since I do intend to use
my laptop internal soundcard for mic and speaker.

I wish the FX2 had an I2S interface!

In my little project, I would like to focus on the implementation of a
96 kHz half-duplex USB soundcard (USB Audio specification)  and a
generic parallel I/O port (USB HID specification). Everything in a
single little board. Anyone on the list interested in joining efforts?

73,

-- Edson

Phil Harman wrote:





Hi Chris,

I have a prototype full duplex USB2 sound card going based on the
Wolfson A/D chip and Xylo/Saxo FPGA board.  At the moment it runs at
48k and 16 bits but the chip can do 192k and 24 bit. Need to walk
first but the pace is picking up!

Writing a generic USB Audio Device driver is way beyond me. Our aim
is to keep the interface to the A/D converter inside the PC as simple


as possible so I don't see the need for a 'real' device driver - we
are not trying to compete with the D44 for example.

73's Phil...VK6APH

Phil....VK6APH



  ----- Original Message -----
  *From:* Christopher T. Day <mailto:CTDay@lbl.gov>
  *To:* xylo-sdr@lists.ae5k.us <mailto:xylo-sdr@lists.ae5k.us>
  *Sent:* Sunday, January 22, 2006 10:29 AM
  *Subject:* [Xylo-SDR] Saxo

  What few useful thoughs I've had so far on the subject agree with
  yours - if possible [does the USB Audio Device spec go as far as
  24-bit stereo, 96/192 ksamples/sec?], the USB-2 interface should
  be able to use a generic USB Audio Device driver => we don't have
  to supply/maintain one for any/all OS. But then, I know almost
  nothing yet,


  Chris - AE6VK





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