usb problem with interrupt transfer 1ms

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Kone

usb problem with interrupt transfer 1ms

Post by Kone » Tue Jan 29, 2008 3:56 pm

Hi everybody,

I want to receive data every 1ms over the interrupt pipe (USB 1.1).
I'm using a Cypress development board which sends every ms 2 bytes in
a frame. I modified the mouse driver source from the ddk and now I
observed a strange behaviour.

I always miss every 2nd frame and the interrupts are only coming every
2ms.

Then I increased the buffer (wMaxPackageSize) up to 16 bytes and then
I could see that always the bytes 3 and 4 are missing the rest of the
16 bytes is OK.

The next test I did: buffer to 32 and I got a similar result: bytes 1
and 2 are OK bytes 3 and 4 are missing and the rest is OK
again---?????

Does anybody know what's going wrong here??? Is it possible to have
more than one buffer, something like double-buffering in the usb
stack???

Thanks in advance,
Kone

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