STM32 USB Audio Class – Windows WASAPI cannot open microphone stream (4 channels)

[MannyMarc35]

Hello,

I am implementing a USB Audio Class 1.0 microphone on an STM32 (Full-Speed only).
The device enumerates correctly on Windows and appears as a 4-channel microphone in the Sound Control Panel, but no WASAPI-based application can open the input stream.

When using Audacity with WASAPI, the device exposes only 1–2 input channels and recording cannot be started.

For USB Audio Class 1.0 Full-Speed microphones on Windows, I have the following questions:

1. Are Sampling Frequency Control requests (GET_CUR / SET_CUR) required even if the device supports only a fixed sample rate of 48 kHz?
2. Is the presence of a Master Feature Unit (Volume and/or Mute control) required for Windows/WASAPI to successfully open the audio stream?
3. Are there any mandatory class-specific control requests that must be implemented (i.e. must not be STALLed) to avoid WASAPI stream open failures?

Setup:

• STM32 USB Device (FS)

• UAC 1.0, Isochronous IN (microphone)

• PCM, 48 kHz, 16 bit, 4 channels

• Iso IN Endpoint: Adaptive

• Windows 11

File with descriptor file is attached below. Thanks in advance!

[FBL]

Hi @MannyMarc35 

Would you provide better details about the STM32H7 product you are using? Are you using reference board ( nucleo or eval board)? Are you using drivers and middleware from CubeH7?