[wdmaudiodev] Re: USB Audio Using Interrupt Transfers

  • From: Udo Eberhardt <Udo.Eb@xxxxxxxxxxx>
  • To: wdmaudiodev@xxxxxxxxxxxxx
  • Date: Thu, 19 Jun 2003 08:38:56 +0200

The introductionary article will help you to choose the right driver model.
Transferring an audio stream by an interrupt pipe should be possible.
However, it is somewhat "unusual".
You need to configure your interrupt endpoint correctly. For example, if
you set it up with a polling interval of 1 ms and a FIFO size of 8 bytes
then you will end up with a rate of 8kbytes/s = 64kbits/s.
Note that you are limited to 64 Bytes FIFO size, means limited to
64kbytes/s.
The priority of interrupt transfers is higher than bulk transfers. The
host controller will poll an interrupt endpoint once per USB frame, if
the polling interval is 1 ms.

Udo Eberhardt
Thesycon GmbH


vrf wrote:
> Dear Udo,
> 
> Thank you! I will review your introduction.
> I think I should prefer method one: write My USBAudio.sys。
> I need 64kbps audio data transfer.
> 
> Are you sure that interrupt Transfers can implement Isochronous Transfers?
> I worry about it because I don't know if the priority of interrupt transfer
> is lower than isochronous transfer in streaming driver when the driver talks
> to usb device.
> I am not sure if the steam implementd by this way could be "like"
> isochronous? :-)
> 
> Any advices are appreciated!
> 
> Best Regards!
> 
> vrf
> 
> ----- Original Message -----
> From: "Udo Eberhardt" <Udo.Eb@xxxxxxxxxxx>
> To: <wdmaudiodev@xxxxxxxxxxxxx>
> Sent: Wednesday, June 18, 2003 11:58 PM
> Subject: [wdmaudiodev] Re: USB Audio Using Interrupt Transfers
> 
> 
> 
>>You have to write a kernel streaming driver that talks to your device in
>>the way your device supports it.
>>For an introduction you can refer to
>>https://www.microsoft.com/whdc/hwdev/tech/audio/wdmaudio.mspx
>>
>>Udo Eberhardt
>>Thesycon GmbH
>>
>>
>>vrf wrote:
>>
>>>Dear all,
>>>
>>>I have a motorola usb module (MC68HC908JB8/MC68HC08JB8/MC68HC08JT8-Rev.
>>>2.0).
>>>Now I need to develop a USB Audio device using it. And the device should
>>>be able to be used by Windows Sound Recorder or NetMeeting as a system
>>>sound device.
>>>As you know, it only supports interrupt transfers. And it has 3
>>>endpoints including control endpoint. Endpoint 1 just has input
>>>direction through which I need to implement a keyboard. Thus ep2 is the
>>>only choice to transfer audio data. How could I implement my project?
>>>
>>>I think there may be two methods:
>>>
>>>Method One:
>>>Describe USB as Audio using interrupt transfers
>>>then, on Host side
>>>CreateFile(Open Device)----->My USBAudio.sys
>>>Method two:
>>>Describe USB as Audio with Isochronous transfers
>>>then, on Host side
>>>CreateFile -----> USBAudio.sys (generic driver supplied by
>>>Microsoft) -----> My Filter Driver
>>>Which solution is good, or there is another better one?
>>>
>>>Any advices are very appreciated!
>>>
>>>Best Regards!
>>>
>>>vrf
>>>2003-06-17
>>
>>
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> 
> 
> 
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