MOUSE(4)                  Special files                  MOUSE(4)

NAME
       mouse - serial mouse interface

CONFIG
       Serial  mice  are  connected to a serial RS232/V24 dialout
       line, see cua(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  synchroni-
       sation 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 but-
       ton is reported by sending a packet with zero movement and
       no  buttons pressed.  (Thus, unlike for the other two but-
       tons, 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 sin-
       gle 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
       cua(4), bm(4)

Linux                   February 10, 1996                       1