NAME | CONFIGURATION | DESCRIPTION | FILES | SEE ALSO | COLOPHON

MOUSE(4)                  Linux Programmer's Manual                 MOUSE(4)

NAME         top

       mouse - serial mouse interface

CONFIGURATION         top

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

DESCRIPTION         top

   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 for 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         top

       /dev/mouse
              A commonly used symbolic link pointing to a mouse device.

SEE ALSO         top

       ttyS(4), gpm(8)

COLOPHON         top

       This page is part of release 4.08 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at
       https://www.kernel.org/doc/man-pages/.

Linux                            2016-10-08                         MOUSE(4)