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isochronous assynchronous transfer troubles

Question asked by SantaGG on Aug 30, 2016

i'm having big troubles with isochronous assynchronous data transfer with feedback. Have spent weeks on the subject, and its all mess in my head now, because simple things who are supposed to work, doesn't, and i don't know what i am missing.
I have a couple questions
1. Do i need to call feedback transfer function from SOF? In examples they do that, but it would make sense to call it at the end of the frame, where there is no risk of host sending a request at the wrong odd/even frame setting. Standard library transfer function sets frame bit for the following frame.
2. In examples in case of incomplete isochronous transfer interrupt they just flush the FIFO(or not even that), while in reference manual dm00031020 they suggest to set endpoint NAK, disable endpoint and only then flush FIFO. Is that important?
3. In the reference manual there is a line (p. 1357, 6.)
"At the “Periodic frame Interval” (controlled by PFIVL in OTG_FS_DCFG), when the
core finds non-empty any of the isochronous IN endpoint FIFOs scheduled for the
current frame non-empty, the core generates an IISOIXFR interrupt in

very likely related, but i can make 0 sense of it.

Any help would be highly appreciated.