From: Mark McDougall (msmcdoug_at_iinet.net.au)
Date: 2008-03-05 14:45:53
Antitrack@networld.at wrote:
> Ouch, such a high speed is really required? What is my USB mouse doing, then?
> Is it also sending the x/y coordinates data at _that_ speed?
> And there is no "inofficial" trick to circumvent the speed problem in sight?
There's a big difference between "bit-bashing" the USB protocol and
supplying regular data packets to the USB slave chip.
To "talk" USB you need to form properly-framed USB packets on the wire,
which as has been mentioned, requires bit rates in the Mbps range. That
means you have to both receive and create the headers and start/stop bits at
the wire signaling rate! You also have packet slots and bandwidth
restrictions which you must adhere to. It simply can't be done, period.
Your mouse, OTOH, sends regular updates to the host via the USB slave chip,
which buffers data and send to the host at most every (IIRC) 10ms - the USB
HID interrupt packet rate. It can choose to send less regularly, especially
if you're not moving the mouse.
Regards,
--
| Mark McDougall | "Electrical Engineers do it
| <http://members.iinet.net.au/~msmcdoug> | with less resistance!"
Message was sent through the cbm-hackers mailing list
Archive generated by hypermail pre-2.1.8.