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Isochronous usb feedback problem and even/odd frame

Question asked by Peter on Sep 14, 2012
Latest reply on Feb 25, 2015 by Chinzei.Tsuneo
Hi
We are developing an audio application with the stm32F405RG that streams the audio from the host asynchronously as a full speed device.

Our problem is that we keep loosing feedback packets (24 bit values) and we suspect that this is the reason to why we get an extraneous noise in the sound, induced by the host.

We suspect that this could be due to that we don't understand the interpretation of even and odd frames on the end point. How are these meant to be programmed in DIEPCTL to be right?

We have set the descriptors to define the IN token to be generated on the feedback end point every 16 frames, which only MacOSX does (Linux and Windows seem to diverge from the standard quite a lot) which leaves us with the problem of how to fill the buffer with accurate feedback values (since we only get a transfer complete interrupt after we actually know a packet was sent). Does anyone know how to handle this?

Best regards,
Peter

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