I'm debugging a userland USB device driver for OS X
that follows the Mass Storage protocol (it's a
vendor-specific device for downloading content to
flash cartridges). There are 6 bulk interfaces on the
device and one interrupt interface. I get
interrmitent/sporadic USB tranction timeout errors
(kIOUSBTransactionTimeout) when trying to read the
status byte of the transaction using ReadPipeTO.
What's interesting is that the command we send it
seems to actually work (set an LED flashing). What
would be some of the reasons why this problem might
happen once in a while? Some kind of timing issue? A
threading issue? Is there a way to debug this short of
breaking out a (very expensive) USB analyzer?
I know this might be hard to answer in a general
sense, but am just wondering if this rings a bell with
anyone, and what are some of the things one might try
in fixing his problem. There's very little
documentation on kIOUSBTransactionTimeout. FWIW, we're
not getting this error in the Windows driver. What's
interesting is that if I hit a breakpoint in the
debugger upon getting the first error of this type, I
don't get errors on any of the other bulk interfaces.
Thanks,
Steve
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