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usb problem with interrupt transfer 1ms

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usb problem with interrupt transfer 1ms

Postby Kone » Tue Jan 29, 2008 2:24 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
Kone
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Joined: Tue Jan 29, 2008 2:10 pm

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