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BF527 Missing NAKs On IN Tokens

Question asked by Dave@CRS on Aug 22, 2011
Latest reply on Sep 6, 2011 by rkarthik

Hi, In my BF527 project I have noticed the following behaviour on the USB OTG peripheral...

 

I have a problem related to my implementation of a CDC device on a BF527, (there are additional endpoints on the same device for UVC class and HID interfaces.

 

When connected to a Windows 7 host, on the BULK IN data endpoint, I observe IN tokens from the host with no NAK token returned by the BF527 hardware, this is reported on my USB analyser as an "Incomplete" transaction.  The missing NAKs are seen on occaisional transactions, this happens even if the processor core is halted, implying that it is behaviour of the peripheral hardware.  My problem being that if there are 3 consecutive missing NAKs the host gives up polling on the endpoint and the device ceases to function.

 

This behaviour is only seen on Windows 7, not on Windows XP or MAC OS.

 

Do you have any suggestions as to the cause of this please.

 

Regards

Dave Fuller

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