MOUSE(4)                  (2020-08-13)                   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 raising it again.  About 14 ms later the mouse will
          send 0x4D (aqMaq) on the data line.  After a further 63 ms, a
          Microsoft-compatible 3-button mouse will send 0x33 (aq3aq).

          The relative mouse movement is sent as dx (positive means
          right) and dy (positive means down).  Various mice can oper-
          ate at different speeds.  To select speeds, cycle through
          the speeds 9600, 4800, 2400, and 1200 bit/s, each time writ-
          ing 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 for synchroniza-
          tion 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:

          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

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        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:

          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 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:

          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

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          2    0    dx6  dx5  dx4  dx3  dx2  dx1  dx0
          3    0    dy6  dy5  dy4  dy3  dy2  dy1  dy0

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

     SEE ALSO
          ttyS(4), gpm(8)

     COLOPHON
          This page is part of release 5.10 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/.

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