[wdmaudiodev] Re: is it possible to build a USB audio device with a CONTROL/BULK/INTERRUPT only USB device controller?

There are plenty of ICs that implement  USB audio devices, TI PCM2902 (already
used this and works fine ), Cmedia CM-108, etc. It's my understanding that usb
audio devices need to implement isochronous transfers and it will not work over
a bulk transfer without some major driver rewriting. Bulk transfers use
unallocated bandwidth and you cannot assure timely delivery of the audio
packets. I don't think its worth the trouble. There are USB controllers that
implement isochronous transfers or you could use a usb codec like the ones
already mentioned.

Dimitri

> Why don't you try UAC3554B from Micronas. It is a complete USB 
> headset, with ADC and DAC and the USB controller, that acts like a 
> standard USB Audio device. I use the codec configuration (UAC3556B), 
> and it works really fine!
> 
> Bests
> Tom
> 
> Aaron Phoenix <aaronphenix@xxxxxxxxx> írta:
> 
> > Hi all,
> > 
> > We are going to build a USB microphone device with a
> > USB device controller, which has four endpoints:
> > -------
> > Endpoint 0: 8-byte FIFO support for Control transfer;
> > Endpoint 1: 64-byte FIFO support for Bulk-In/Bulk-Out
> > transfer;
> > Endpoint 2: 8-byte FIFO support for
> > Bulk-Out/Interrupt-Out transfer;
> > Endpoint 3: 64-byte FIFO support for
> > Interrupt-In/Bulk-In Transfer.
> > -------
> > 
> > Now there is a USBD_STATUS_STALL_PID error when the
> > call URB_FUNCTION_SELECT_CONFIGURATION returns. Here
> > are the debug messages from firmware:
> > -------
> > reset
> > reset
> > [80 06 00 01 00 00 40 00] USB_DT_DEVICE, ok
> > reset
> > [80 06 00 01 00 00 12 00] USB_DT_DEVICE, ok
> > [80 06 00 02 00 00 09 00] USB_DT_CONFIG, ok
> > [80 06 00 02 00 00 FF 00] USB_DT_CONFIG, ok
> > [80 06 00 03 00 00 FF 00] USB_DT_STRING, ok
> > [80 06 02 03 09 04 FF 00] USB_DT_STRING, ok
> > [80 06 00 03 00 00 FF 00] USB_DT_STRING, ok
> > [80 06 02 03 09 04 FF 00] USB_DT_STRING, ok
> > [80 06 00 01 00 00 12 00] USB_DT_DEVICE, ok
> > [80 06 00 02 00 00 09 00] USB_DT_CONFIG, ok
> > [80 06 00 02 00 00 64 00] USB_DT_CONFIG, ok
> > -->error, firmware dectects the STALL status.
> > -------
> > 
> > This USB device controller automatically responds to
> > 
> SET_CONFIGURATION/GET_CONFIGURATION/SET_FEATURE/CLEAR_FEAT
> URE/SET_INTERFACE/GET_INTERFACE/SET_ADDRESS/GET_STATUS.
> > And we have made USB Mass Storage and USB HID
> > mouse&keyboard devices with this chip, all they work
> > well.
> > 
> > Is it possible to build a USB audio device needs
> > Isochronous pipes with a Bulk-only USB device
> > controller? How do the values of bmAttributes field of
> > Endpoint Descriptor affect the host&device
> > controllers? We need the expert opinions to decide to
> > give up or go on with the project. Thank you!
> > 
> > Regards,
> > Aaron M. Phoenix
> > 
> > 
> > 
> >             
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