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serial_graphics_tablet [2007/07/26 16:32] (current)
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 +Below is an edited extract from an [[http://​​group/​mod.mac/​browse_thread/​thread/​d6cec207212feaa1/​82203172bc987e03?​lnk=st&​q=summagraphics+mactablet+driver+&​rnum=8&​hl=en#​82203172bc987e03| email I found]] on Google'​s Usenet Archive. ​ I think there is enough information in there to allow us to use some older serial port graphics tablets as X-Y controllers under MIOS. 
 +If you are the original author of this post and wish to have it removed, please contact me through the Private Messages at​forum
 +''​Date:​ Sat, 26 Jul 86 09:12:59 pdt''​\\
 +''​From:​ oster%ucbla...@BERKELEY.EDU (David Phillip Oster)''​\\
 +''​Subject:​ Re: Digitizing point coordinates (MacTablet)''​\\
 +This letter discusses using Mac compatible digitizing tablets to get high
 +resolution data ... since you are not afraid to program, you might try the following:
 +I assume the MacTablet connects to the Mac using a serial port...
 +Listen to the tablet using terminal software (Versaterm, naacterm ...)(try 9600 baud as an initial guess at the baud rate.)
 +The tablet probably sends a 5 byte data packet of the following form:
 +^  b7^  b6^  b5^  b4^  b3^  b2^  b1^  b0|bits of a byte  |
 +|  P|  1|  0|  0|  0|  S|  0|  0|P is parity. ​ S is on if switch is down  |
 +|  P|  0|  x5|  x4|  x3|  x2|  x1|  x0|low 6 bits of x data  |
 +|  P|  0|  x11|  x10|  x9|  x8|  x7|  b6|high 6 bits of x data  |
 +|  P|  0|  y5|  y4|  y3|  y2|  y1|  y0|low 6 bits y data  |
 +|  P|  0|  y11|  y10|  y9|  y8|  y7|  y6|high 6 bits y data  |
 +b6 is 1 only at the start of a 5 byte data packet.
 +This data is drawn from a Summagraphics data sheet for their Bit Pad 1
 +Unlike the Mac, point (0,0) is probably at the LOWER-left corner.
 +If you get data that is consistent with this, then you need only write a
 +basic program to read data at the serial port.  Tablets generate so much data
 +that you're program had better check the fullness of the serial buffer and
 +throw away 5 byte data packets periodically to keep the buffer from
 +overflowing. ​ Alternatively,​ you could write in a language, like C or
 +compiled Pascal, that was fast enough to keep up with the data rate.
 +Low-resolution Kurta tablets and other-than-MacTablet Summagraphic tablets use this data format when they
 +are not transmitting data as strings of ASCII, base-10 integers.
 +Kurta'​s PenMouse, a cordless digitizer considerably cheaper than
 +MacTablet, sends 2400 baud, their other models generally run at 4800 baud.
 +Kurta also makes a MacXL compatible version.
 +Disclaimer: My opinions are solely my own, but, in evaluating them, you
 +should know that I am currently re-writing Kurta'​s software.
 +--- David Phillip Oster         -- "The goal of Computer Science is to\\
 +Arpa: ​ -- build something that will last at\\
 +Uucp: ucbvax!ucblapis!oster ​    -- least until we've finished building it."\\
serial_graphics_tablet.txt ยท Last modified: 2007/07/26 16:32 (external edit)