MOUSE(4)

NAME
mouse - serial mouse interface

CONFIG
Serial mice are connected to a serial RS232/V24 dialout line, see cua(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. About 14 ms later the mouse will send 0x4D on the data line. After a further 63 ms, Microsoft-compatible mice will send 0x33. Other mice send different values.

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 synchronisation 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 | dx7
2 | 0 | dx5 | dx4 | dx3 | dx2 | dx1 | dx0
3 | 0 | dy5 | dy4 | dy3 | dy2 | dy1 | dy0
Original Microsoft mice only have two buttons. However, there are some three button mice which also use the Microsoft protocol. Pressing the third button is reported by sending a packet with zero movement and no buttons pressed.

  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 | ? | ? | ? | ? | lb | mb | rb
2 | 0 | dxa6 | dxa5 | dxa4 | dxa3 | dxa2 | dxa1 | dxa0
3 | 0 | dxb6 | dxb5 | dxb4 | dxb3 | dxb2 | dxb1 | dxb0
4 | 0 | dya6 | dya5 | dya4 | dya3 | dya2 | dya1 | dya0
5 | 0 | dyb6 | dyb5 | dyb4 | dyb3 | dyb2 | dyb1 | dyb0

  Sun protocol
The Sun 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 3-byte packets. dx is sent as single two's-complement value, dy as negated two's-complement value. lb (mb, rb) are cleared when the left (middle, right) button is pressed:
byte | d7 | d6 | d5 | d4 | d3 | d2 | d1 | d0
1 | 1 | ? | ? | ? | ? | lb | mb | rb
2 | 0 | dx6 | dx5 | dx4 | dx3 | dx2 | dx1 | dx0
3 | 0 | dy6 | dy5 | dy4 | dy3 | dy2 | dy1 | dy0

  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 | ? | ? | 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
cua(4), bm(4)