Hi,
I am currently working on an USB-Audio device based on a AT91SAM7 processor. Actually I am currently trying to get the asynchronous mode working, to be able to use the AT91SAM7 as I2S transmitter in slave mode, utilizing and external clock. So I added the endpoint descriptors for the Feedback pipe. I attached the lsusb output. Alsa detects the card properly and reports it to be async in the /proc/asound interface. Now for a first tested I am trying to report back a constant rate through the feedback pipe. The stream is 48kHz with 16Bit. Reading the USB Audio 1.0 spec I assume in theory for a 48kHz stream I would report a rate of 48 samples per frame to the host, compensated by the measured drift. As the data should be 10.14 encoded I currently send { 0x0c, 0x00, 0x00 } on the feedback pipe whenever it is queried, which happens whenever I try to play some stream on this device. But unfortunately the host won't send any data to the device. I am wondering what might be wrong and where to check that alsa received the feedback data properly?
I would be really thankful for any help!
Regards, Julian