Re: Need a driver for USB Tablet

On Fri, Feb 16, 2007 at 04:38:03PM -0500, Mazin wrote:

> >Go ahead and post the protocol.
> OK, here goes.

It looks fine - like what one would expect from a simple tablet. Can you
add the USB descriptor listing from lsusb -vvv?

> 
> The tablet sends its data in an 8-byte packet.
> (Numbers in hex)
> 
> A typical packet looks like:
> 07 80 4f 00 4a 0b 00 00
> 
> The bytes, from left-to-right, are:
> 1: ? Not sure, but from my testing it's always 07
> 2: The button codes for when buttons are pressed (there are two buttons 
> on the barrel of the pen):
>    81 = Pen tip touch (translates to LMB)
>    82 = Bottom side button (closest to pen tip)
>    84 = Top side button (translates to RMB)
>    C0 = I'm not sure, but I think it might indicate when the pen is not 
> in the sensing range of the tablet.
> 3: X-pos small increment (from 00 to FF)
> 4: X-pos large increment (goes up to 0F).  Each one of these is "worth" 
> 256, since byte three can only count to FF.
> 5: Y-pos small increment (from 00-FF)
> 6: Y-pos large increment (goes up to 0B).  Works like the X-pos.
> 7: Pen pressure (goes up to FF)
> 8: Pressure large increment, "worth" 256.  My tablet has 512 degrees of 
> pressure, so for 512, byte seven is FF and byte 8 is 01.  On my tablet 
> it's either 00 or 01, but tablets with a greater pressure range may have 
> higher values.
> 
> I'm not a USB expert, but I suspect that something special happens when 
> the tablet is first plugged in.  For brevity's sake, I have the raw 
> sniffer data from when I first plug my tablet in on a computer with the 
> Windows driver installed.  You can find it at 
> http://files.aztekera.com/apps/tabletinitialization.txt
> 
> If this isn't enough I can provide more data, although I might not know 
> what to do with it.
> 
> As always, thanks for any support,
> Mazin
> 

-- 
Vojtech Pavlik
Director SuSE Labs

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