Author Topic: USE_USB_AUDIO  (Read 127 times)

Offline Phil

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USE_USB_AUDIO
« on: October 27, 2020, 12:49:18 AM »
Mark, et. al,

I am considering the USB Audio interface for a upcoming project.

I am receiving an analog or digital (I2S) SAI stream from a microphone source. I'd like to use the NXP MK64 processor to output the microphone source as a USB Audio Device so a Windows-based PC can recognize and use the microphone audio source. However, it is important that the USB is seen by Windows as a USB Audio Class Device so as to be usable in Skype or other soft codecs.

I can provide the audio in analog or digital format. I would think it would be better to keep this in the digital domain (I2S)?

I am thinking about using a MK66 with (2) USB ports, utilizing one for USB Audio and the other for firmware updates, CDC, etc.  Any concerns about this idea?

Thank you for your opinion.

Phil

Offline mark

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Re: USE_USB_AUDIO
« Reply #1 on: October 27, 2020, 06:52:31 PM »
Hi Phil

See the USB audio guide at https://www.utasker.com/docs/uTasker/uTaskerUSB_Audio.pdf

If you have the audio stream in digital form it is good although there is still the question of whether the format is suitable as it is for the USB audio channel - in the worst case it needs to be converted from its input format to the one needed by the USB channel.

Whether there is one or two USB interfaces you can also use a composite to allow audio and other uses on the same USB device connection.

K66 allows two USB devices (or mixtures of device and host) to be used in parallel and the K66 has a high speed USB interface for faster data transfer.

Therefore you shouldn't have any real difficulties to do what you need.

Regards

Mark

Offline Phil

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Re: USE_USB_AUDIO
« Reply #2 on: October 28, 2020, 04:22:16 AM »
Thank you, Mark.

I did read the uTasker USB Audio documentation prior to my last post.

My main issue was whether or not I could generate a USB Audio Class descriptor using the K64/K66 solution.  It is very important that the audio stream be recognized by Windows or Macs. You have given me more confidence that I have the correct design in mind.

Thank you again.

Phil

Offline mark

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Re: USE_USB_AUDIO
« Reply #3 on: October 28, 2020, 12:43:54 PM »
Phil

The descriptors in the audio reference are recognised by Windows (I don't know about Mac and Linux but I don't expect problems since they should be following the same USB standards). No driver is required by Windows so it automatically appears as additional microphone.

Recently I developed a ultrasound stereo microphone product which worked at 384ksps on each channel (K66 HS USB) which worked immediately with Windows and standard sound processing tools.
The attached PDF shows the isochronous processing involved, plus the descriptors used.

Regards

Mark

Offline Phil

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Re: USE_USB_AUDIO
« Reply #4 on: October 28, 2020, 04:04:43 PM »
Thank you, Mark.

I will study these descriptors closely.  Great information!

Phil