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



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:

       center; r c l.  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 rais-
       ing  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:

       center; l l.  bit/s     string 9600 *q 4800 *p 2400 *o 1200 *n

       The first byte of a data packet can be  used  to  synchronization  pur-
       poses.

   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:

       center; r  c  c  c  c  c  c  c.   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  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 Micro-
       soft 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 val-
       ues,  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:

       center; r c c c c c c c c.   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 pack-
       ets.  dx and dy are sent as single signed values, the sign bit indicat-
       ing a negative value.  lb (mb, rb)  are  set  when  the  left  (middle,
       right) button is pressed:

       center;  r c c c c c c c c.  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
       This page is part of release 3.05 of the Linux  man-pages  project.   A
       description  of  the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.



Linux                             1996-02-10                          MOUSE(4)