1TB(4)                      Kernel Interfaces Manual                      TB(4)
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NAME

6       tb - line discipline for digitizing devices
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SYNOPSIS

9       /sys/conf/SYSTEM:
10            NTB  1    # RS232 interface for Genisco/Hitachi tablets
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DESCRIPTION

13       This  line  discipline provides a polled interface to many common digi‐
14       tizing devices which are connected to a host  through  a  serial  line.
15       When  these devices stream data at high speed, the use of the line dis‐
16       cipline is critical in minimizing the number of samples that would oth‐
17       erwise be lost due to buffer exhaustion in the tty(4) handler.
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19       The line discipline is enabled by a sequence:
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21            #include <sys/tablet.h>
22            int ldisc = TBLDISC, fildes; ...
23            ioctl(fildes, TIOCSETD, &ldisc);
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25       A typical application program then polls the digitizing device by read‐
26       ing a binary data structure which contains: the current X and  Y  posi‐
27       tions  (in  the device coordinate space), up-down status of the buttons
28       or pen stylus, proximity information (when available), and a  count  of
29       the  number  of  samples  received  from  the input device since it was
30       opened.  In addition, devices such as the GTCO append tilt and pressure
31       information to the end of the aforementioned structure.  For the Polhe‐
32       mus 3-D digitizer the structure read is completely different. Refer  to
33       the include file for a complete description.
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35       While  in  tablet mode, normal teletype input and output functions take
36       place.  Thus, if an 8 bit output data path is desired, it is  necessary
37       to  prepare the output line by putting it into RAW mode using ioctl(2).
38       This must be done before changing the discipline with TIOCSETD, as most
39       ioctl(2) calls are disabled while in tablet line-discipline mode.
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41       The line discipline supports ioctl(2) requests to get/set the operating
42       mode, and to get/set the tablet type and operating mode by  or-ing  the
43       two values together.
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45       The  line  discipline  supports digitizing devices which are compatible
46       with Hitachi, GTCO, or Polhemus protocol formats.   For  Hitachi  there
47       are  several  formats  with  that used in the newer model HDG-1111B the
48       most common.
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SEE ALSO

51       tty(4)
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DIAGNOSTICS

54       None.
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583rd Berkeley Distribution       August 1, 1987                           TB(4)