USB interrupt endpoint limitations

J

J.R. Heisey

1) The endpoint descriptor has a minimum value of 1 ms polling period.

Therefore it would seem that I can get a maximum of 1000 packets per
second with each packet
containing a maximum of 64 bytes of payload data.

Maximum throughput then limited to 64000 bytes per second.

Anyone disagree with this assessment?

2) On some computers it appears that though my USB device requests 1 ms
interrupt endpoint
polling the actual polling rate is 2 ms.

Can anyone confirm this experience and explain it? Or better yet, tell
me how to correct it.

Thanks,
J.R. Heisey
Synaptics, Inc.
 

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