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NAME

       mouse - serial mouse interface

CONFIGURATION

       Serial  mice  are  connected  to  a  serial RS232/V24 dialout line, see
       ttyS(4) for a description.

DESCRIPTION

   Introduction
       The pinout of the usual 9 pin plug as used for serial mice is:

                          pin   name   used for
                            2    RX    Data
                            3    TX    -12 V, Imax = 10 mA
                            4   DTR    +12 V, Imax = 10 mA
                            7   RTS    +12 V, Imax = 10 mA
                            5   GND    Ground

       This is the specification, in fact 9 V suffices with most mice.

       The mouse driver can recognize a mouse  by  dropping  RTS  to  low  and
       raising  it again.  About 14 ms later the mouse will send 0x4D ('M') on
       the data line.  After a further 63 ms, a Microsoft-compatible  3-button
       mouse will send 0x33 ('3').

       The relative mouse movement is sent as dx (positive means right) and dy
       (positive means down).  Various mice can operate at  different  speeds.
       To  select  speeds,  cycle through the speeds 9600, 4800, 2400 and 1200
       bit/s, each time writing the two characters from the  table  below  and
       waiting  0.1  seconds.   The following table shows available speeds and
       the strings that select them:

                                   bit/s   string
                                   9600    *q
                                   4800    *p
                                   2400    *o
                                   1200    *n

       The first byte  of  a  data  packet  can  be  used  to  synchronization
       purposes.

   Microsoft protocol
       The Microsoft protocol uses 1 start bit, 7 data bits, no parity and one
       stop bit at the speed of 1200 bits/sec.  Data is sent to RxD in  3-byte
       packets.  The dx and dy movements are sent as two's-complement, lb (rb)
       are set when the left (right) button is pressed:

                    byte   d6   d5    d4    d3    d2    d1    d0
                       1   1    lb    rb    dy7   dy6   dx7   dx6
                       2   0    dx5   dx4   dx3   dx2   dx1   dx0
                       3   0    dy5   dy4   dy3   dy2   dy1   dy0

   3-button Microsoft protocol
       Original Microsoft mice only have two buttons.  However, there are some
       three  button  mice which also use the Microsoft protocol.  Pressing or
       releasing the middle button is reported by sending a packet  with  zero
       movement  and  no  buttons  pressed.   (Thus,  unlike for the other two
       buttons, the status of the  middle  button  is  not  reported  in  each
       packet.)

   Logitech protocol
       Logitech  serial  3-button  mice  use  a  different  extension  of  the
       Microsoft protocol: when the middle button  is  up,  the  above  3-byte
       packet  is  sent.   When  the  middle button is down a 4-byte packet is
       sent, where the 4th byte has value 0x20 (or at least has the  0x20  bit
       set).   In  particular,  a  press  of  the middle button is reported as
       0,0,0,0x20 when no other buttons are down.

   Mousesystems protocol
       The Mousesystems protocol uses 1 start bit, 8 data bits, no parity  and
       two  stop  bits  at the speed of 1200 bits/sec.  Data is sent to RxD in
       5-byte packets.  dx is sent as the  sum  of  the  two  two's-complement
       values,  dy  is send as negated sum of the two two's-complement values.
       lb (mb, rb) are  cleared  when  the  left  (middle,  right)  button  is
       pressed:

             byte   d7    d6     d5     d4     d3     d2     d1     d0
                1   1     0      0      0      0      lb     mb     rb
                2   0    dxa6   dxa5   dxa4   dxa3   dxa2   dxa1   dxa0
                3   0    dya6   dya5   dya4   dya3   dya2   dya1   dya0
                4   0    dxb6   dxb5   dxb4   dxb3   dxb2   dxb1   dxb0
                5   0    dyb6   dyb5   dyb4   dyb3   dyb2   dyb1   dyb0

       Bytes  4  and  5  describe the change that occurred since bytes 2 and 3
       were transmitted.

   Sun protocol
       The Sun protocol is the 3-byte version of the above 5-byte Mousesystems
       protocol: the last two bytes are not sent.

   MM protocol
       The  MM protocol uses 1 start bit, 8 data bits, odd parity and one stop
       bit at the speed of 1200 bits/sec.  Data  is  sent  to  RxD  in  3-byte
       packets.   dx  and  dy  are  sent as single signed values, the sign bit
       indicating a negative value.   lb  (mb,  rb)  are  set  when  the  left
       (middle, right) button is pressed:

                 byte   d7   d6    d5    d4    d3    d2    d1    d0
                    1   1     0     0    dxs   dys   lb    mb    rb
                    2   0    dx6   dx5   dx4   dx3   dx2   dx1   dx0
                    3   0    dy6   dy5   dy4   dy3   dy2   dy1   dy0

FILES

       /dev/mouse
              A commonly used symlink pointing to a mouse device.

SEE ALSO

       ttyS(4), gpm(8)

COLOPHON

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