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:
- Are Sampling Frequency Control requests (GET_CUR / SET_CUR) required even if the device supports only a fixed sample rate of 48 kHz?
- Is the presence of a Master Feature Unit (Volume and/or Mute control) required for Windows/WASAPI to successfully open the audio stream?
- 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!
