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:

							    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

       This  page is part of release 3.25 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)