Beware that this post is related to an SDK in maintenance mode
More Info: Consider nRF Connect SDK for new designs
This post is older than 2 years and might not be relevant anymore
More Info: Consider searching for newer posts

USB Audio Sampling Rates

What frequencies for USB Audio are supported in the NRF52840?

Parents
  • 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

     

  • 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

Reply
  • 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

Children
Related