USB Audio Sampling Rates

RE: USB Audio Sampling Rates

Or — Tue, 17 Sep 2019 20:38:19 GMT

Can you please post the code you have that does what you mention here ?

RE: USB Audio Sampling Rates

lCannon — Mon, 29 Apr 2019 18:00:20 GMT

Starting with the USB audio example, I removed the USB headphone device to just have the microphone. The sof events for the microphone were piggy backing off the headphone events so with the headphone removed, the microphone needed an sof interrupt handler registered. Also, I changed the channels to one and the mic terminal channel config to only the left front. I have software that outputs a nice sounding sine wave at 1 KHz with the example’s 48000 Hz sapling rate. However, when I change the sampling rate to use any of the other standardized frequencies that are supported, the audio has severe artifacting. I would think it should work fine with the change being the pitch of the generated sine wave. Are there other changes required other than the frequency specified in the microphone audio format description that I am missing? The only standard sampling rate that seems to work without an issue is the 48 KHz.

Thank you

RE: USB Audio Sampling Rates

cyberluke — Tue, 29 Jan 2019 22:53:33 GMT

Hi, any example for implementing this? At least partial USBHid plus firmware advice, which way to go in terms of NRF5 SDK.

RE: USB Audio Sampling Rates

Håkon Alseth — Tue, 17 Apr 2018 10:39:45 GMT

That should be fine, as long as you use the "standardized frequencies", like 16/32/44.1/48.

You can find more info on the USB audio class here: http://www.usb.org/developers/docs/devclass_docs/

Cheers,

Håkon

RE: USB Audio Sampling Rates

Andrew — Mon, 16 Apr 2018 17:53:09 GMT

Should there be any trouble then in decreasing the frequency?

RE: USB Audio Sampling Rates

Håkon Alseth — Mon, 16 Apr 2018 12:06:27 GMT

Hi,

The USB device (USBD) controller on nRF52840 implements a full speed USB device function that meets 2.0 revision of the USB specification.

This means that USBD peripheral is 2.0 compliant, but has a limitation of 12 MBit PHY (full speed physical layer).

The USB audio class for full speed devices supports stereo, up to 48 kHz sampling rate, as described in this article:

https://www.edn.com/design/consumer/4376143/Fundamentals-of-USB-Audio

Best regards,

Håkon