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25 .TH MOUSE 4 2020-08-13 "Linux" "Linux Programmer's Manual"
26 .SH NAME
27 mouse \- serial mouse interface
28 .SH CONFIGURATION
29 Serial mice are connected to a serial RS232/V24 dialout line, see
30 .BR ttyS (4)
31 for a description.
32 .SH DESCRIPTION
33 .SS Introduction
34 The pinout of the usual 9 pin plug as used for serial mice is:
35 .PP
36 .TS
37 center;
38 r c l.
39 pin name used for
40 2 RX Data
41 3 TX \-12 V, Imax = 10 mA
42 4 DTR +12 V, Imax = 10 mA
43 7 RTS +12 V, Imax = 10 mA
44 5 GND Ground
45 .TE
46 .PP
47 This is the specification, in fact 9 V suffices with most mice.
48 .PP
49 The mouse driver can recognize a mouse by dropping RTS to low and raising
50 it again.
51 About 14 ms later the mouse will send 0x4D (\(aqM\(aq) on the data line.
52 After a further 63 ms, a Microsoft-compatible 3-button mouse will send
53 0x33 (\(aq3\(aq).
54 .PP
55 The relative mouse movement is sent as
56 .I dx
57 (positive means right)
58 and
59 .I dy
60 (positive means down).
61 Various mice can operate at different speeds.
62 To select speeds, cycle through the
63 speeds 9600, 4800, 2400, and 1200 bit/s, each time writing the two characters
64 from the table below and waiting 0.1 seconds.
65 The following table shows available speeds and the strings that select them:
66 .PP
67 .TS
68 center;
69 l l.
70 bit/s string
71 9600 *q
72 4800 *p
73 2400 *o
74 1200 *n
75 .TE
76 .PP
77 The first byte of a data packet can be used for synchronization purposes.
78 .SS Microsoft protocol
79 The
80 .B Microsoft
81 protocol uses 1 start bit, 7 data bits, no parity
82 and one stop bit at the speed of 1200 bits/sec.
83 Data is sent to RxD in 3-byte packets.
84 The
85 .IR dx
86 and
87 .I dy
88 movements are sent as
89 two's-complement,
90 .I lb
91 .RI ( rb )
92 are set when the left (right)
93 button is pressed:
94 .PP
95 .TS
96 center;
97 r c c c c c c c.
98 byte d6 d5 d4 d3 d2 d1 d0
99 1 1 lb rb dy7 dy6 dx7 dx6
100 2 0 dx5 dx4 dx3 dx2 dx1 dx0
101 3 0 dy5 dy4 dy3 dy2 dy1 dy0
102 .TE
103 .SS 3-button Microsoft protocol
104 Original Microsoft mice only have two buttons.
105 However, there are some
106 three button mice which also use the Microsoft protocol.
107 Pressing or
108 releasing the middle button is reported by sending a packet with zero
109 movement and no buttons pressed.
110 (Thus, unlike for the other two buttons, the status of the middle
111 button is not reported in each packet.)
112 .SS Logitech protocol
113 Logitech serial 3-button mice use a different extension of the
114 Microsoft protocol: when the middle button is up, the above 3-byte
115 packet is sent.
116 When the middle button is down a 4-byte packet is
117 sent, where the 4th byte has value 0x20 (or at least has the 0x20
118 bit set).
119 In particular, a press of the middle button is reported
120 as 0,0,0,0x20 when no other buttons are down.
121 .SS Mousesystems protocol
122 The
123 .B Mousesystems
124 protocol uses 1 start bit, 8 data bits, no parity,
125 and two stop bits at the speed of 1200 bits/sec.
126 Data is sent to RxD in
127 5-byte packets.
128 .I dx
129 is sent as the sum of the two two's-complement
130 values,
131 .I dy
132 is send as negated sum of the two two's-complement
133 values.
134 .I lb
135 .RI ( mb ,
136 .IR rb )
137 are cleared when the left (middle,
138 right) button is pressed:
139 .PP
140 .TS
141 center;
142 r c c c c c c c c.
143 byte d7 d6 d5 d4 d3 d2 d1 d0
144 1 1 0 0 0 0 lb mb rb
145 2 0 dxa6 dxa5 dxa4 dxa3 dxa2 dxa1 dxa0
146 3 0 dya6 dya5 dya4 dya3 dya2 dya1 dya0
147 4 0 dxb6 dxb5 dxb4 dxb3 dxb2 dxb1 dxb0
148 5 0 dyb6 dyb5 dyb4 dyb3 dyb2 dyb1 dyb0
149 .TE
150 .PP
151 Bytes 4 and 5 describe the change that occurred since bytes 2 and 3
152 were transmitted.
153 .SS Sun protocol
154 The
155 .B Sun
156 protocol is the 3-byte version of the above 5-byte
157 Mousesystems protocol: the last two bytes are not sent.
158 .SS MM protocol
159 The
160 .B MM
161 protocol uses 1 start bit, 8 data bits, odd parity, and one
162 stop bit at the speed of 1200 bits/sec.
163 Data is sent to RxD in 3-byte
164 packets.
165 .I dx
166 and
167 .I dy
168 are sent as single signed values, the
169 sign bit indicating a negative value.
170 .I lb
171 .RI ( mb ,
172 .IR rb )
173 are
174 set when the left (middle, right) button is pressed:
175 .PP
176 .TS
177 center;
178 r c c c c c c c c.
179 byte d7 d6 d5 d4 d3 d2 d1 d0
180 1 1 0 0 dxs dys lb mb rb
181 2 0 dx6 dx5 dx4 dx3 dx2 dx1 dx0
182 3 0 dy6 dy5 dy4 dy3 dy2 dy1 dy0
183 .TE
184 .SH FILES
185 .TP
186 .I /dev/mouse
187 A commonly used symbolic link pointing to a mouse device.
188 .SH SEE ALSO
189 .BR ttyS (4),
190 .BR gpm (8)