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Re: [Xylo-SDR] Saxo
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.
From: Edson Pereira [mailto:email@example.com]
Sent: Saturday, January 21, 2006 9:32 PM
To: Xylo-SDR Discussion
Subject: Re: [Xylo-SDR] Saxo
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
Phil Harman wrote:
>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
>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
>73's Phil... VK6APH
>----- Original Message -----
>From: "Edson Pereira" <firstname.lastname@example.org>
>To: "Xylo-SDR Discussion" <email@example.com>
>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?
>>Phil Harman wrote:
>>>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.
>>> ----- Original Message -----
>>> *From:* Christopher T. Day <mailto:CTDay@lbl.gov>
>>> *To:* firstname.lastname@example.org <mailto:email@example.com>
>>> *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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