Numonics graphics tablet protocol?

Jan-Benedict Glaw jbglaw at
Mon Aug 7 16:32:24 CDT 2006

On Mon, 2006-08-07 22:20:32 +0000, Jules Richardson <julesrichardsonuk at> wrote:
> I managed to guess DIP switch settings and serial line settings to a point 
> that I can get useful ASCII data out of the tablet (coordinates and button 
> info) - but if I could interpret the packed binary stream hopefully it'd 
> make the tablet seem a lot more responsive...

Usually, these packets are quite easy to decipher.

Just capture the serial stream and move the pen horizonthally (maybe
along the top or bottem line), then look at the stream. The x
coordinate should be easy to guess.

Repeat with a vertical line.

Repeat with buttons or varying preassure.

Most of the tablets I know set the most significant bit of a packet's
first packet to allow for easy packet-start scanning. (The downside is
that all following bytes waste one bit because the high-bit cannot be


       Jan-Benedict Glaw       jbglaw at                +49-172-7608481
Signature of:          God put me on earth to accomplish a certain number of things.
the second  :                      Right now I am so far behind I will never die.

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