I am using the frdmkl25z_usb_examples_usb_device_audio_generator_bm as a starting point to develop a full duplex USB audio interface on the FRDM-KL25Z evaluation board.
It wasn't a big deal to change the original example to a 48 kHz sampling rate and 16 bit samples in stereo. But then I got completely stuck setting up the audio-out endpoint and interface.
Attached is my descriptor file. While I am pretty confident that the USB descriptor is correct, I have no clue about the descriptor replica that has to be setup for the USB library to work - unluckily I couldn't find any documentation.
Could please someone with more knowledge about this USB implementation give me some hint!?
Here is also a printout of the USB BDT.
It shows that Interrupt In-Endpoint 0x81 (BD starting at 0x1ffff620) is never used (Volume is updated via EP 0) and that Isochronous In-Endpoint 0x82 is setup and used correctly (BD at 0x1ffff650).
Isochronous Out-Endpoint 0x02 (BD at 0x1ffff640) has been set, but for unknown reasons never starts to work. More, the out-ep does not cause any USB Interrupts, while the working in-ep does nicely every 1 ms.
Any help is welcome!
Original Attachment has been moved to: usb_device_descriptor.c.zip