I'm trying the usb audio examples in SDK_2.0 on a TWR-K24F120M and I cannot get usb_device_audio_speaker to work. The USB portion of the example seems to work fine, with the speaker being correctly detected and enumerated by the host, and audio data flowing over USB. The problem is the DMA transfer to the codec: SAI_TransferSendEDMA() is called, but the associated callback() never gets called.
Other audio examples that use that mechanism work fine, in particular demo_apps/sai and driver_examples/sai/sai_edma_transfer.c have the same callback() called, and produce sound as expected.
Can anyone suggest how to troubleshoot this?