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:
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:
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:
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:
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:
FILES
/dev/mouse
A commonly used symbolic link pointing to a mouse device.
SEE ALSO
COLOPHON
This page is part of release 5.09 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/.