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211 lines
7.9 KiB
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211 lines
7.9 KiB
Plaintext
SOURCE: http://www.kryslix.com/nsfaq/Q.12.html
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Subject: What protocol do mice use?
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Date: 09/16/97
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Updated: 11/16/00 This document was adapated from a web page produced by
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Tomi Engdahl <then@delta.hut.fi>
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Microsoft serial mouse
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Description
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The Microsoft serial mouse is the most popular 2 button mouse. It is
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supported by all major operating systems. The maximum tracking rate for
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a Microsoft mouse is 40 reports/second * 127 counts per report, in other
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words, 5080 counts per second. The most common range for mice is is 100
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to 400 CPI (counts per inch) but can be up to 1000 CPI. A 100CPI mouse
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can discriminate motion up to 50.8 inches/second while a 400 CPI mouse
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can only discriminate motion up to 12.7 inches/second.
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Pinout
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9 pin 25 pin Line Comments
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shell 1 GND
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3 2 TD Serial data from host to mouse (only for power)
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2 3 RD Serial data from mouse to host
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7 4 RTS Positive voltage to mouse
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8 5 CTS
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6 6 DSR
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5 7 SGND
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4 20 DTR Positive voltage to mouse and reset/detection
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RTS = Request to Send CTS = Clear to Send
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DSR = Data Set Ready DTR = Data Terminal Ready
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GND = Protective Ground SGND = Signal Ground
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To function correctly, both the RTS and DTR lines must be
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positive. DTR/DSR and RTS/CTS must NOT be shorted. RTS may be toggled
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negative for at least 100ms to reset the mouse. (After a cold boot, the
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RTS line is usually negative. This provides an automatic toggle when
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RTS is brought positive). When DTR is toggled the mouse should send a
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single byte 0x45 (ASCII 'M').
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Serial data parameters:
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1200bps, 7 databits, 1 stop-bit
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Data packet format:
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Data is sent in 3 byte packets for each event (a button is pressed or
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released or the mouse moves):
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D7 D6 D5 D4 D3 D2 D1 D0
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Byte 1 X 1 LB RB Y7 Y6 X7 X6
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Byte 2 X 0 X5 X4 X3 X2 X1 X0
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Byte 3 X 0 Y5 Y4 Y3 Y2 Y1 Y0
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LB is the state of the left button (1 means down)
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RB is the state of the right button (1 means down)
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X7-X0 movement in X direction since last packet (signed byte)
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Y7-Y0 movement in Y direction since last packet (signed byte)
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The high order bit of each byte (D7) is ignored. Bit D6 indicates the start of an event, which allows the software to synchronize with the mouse.
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Graphical representation of a packet
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1st byte 2nd byte 3rd byte
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================ =============== ================
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- 1 ? ? Y Y X X - 0 X X X X X X - 0 Y Y Y Y Y Y
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================ =============== ================
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| | \ / \ / \---------/ \---------/
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| | | | | |
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| | | \----\ | |
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| | \--------|-------|--------\ |
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| | / \ /---------\ / \ /---------\
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| | ================ =================
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| | 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
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Left Button --/ | ================ =================
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Right Button ----/ X increment Y increment
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3 Button Logitech extension
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Logitech extended the 2 button mouse protocol to support 3 button mice
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by adding a 4th byte when the middle button is pressed (and the first
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packet after it is released). If a 4th byte is encountered (i.e., an
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extra byte with D6 set to 0) then D5 of that byte (0x20) indicates the
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status of the middle mouse button.
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Mouse systems mouse
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Serial data parameters:
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1200bps, 8 databits, 1 stop-bit
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5 byte Mouse Systems packet
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D7 D6 D5 D4 D3 D2 D1 D0
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Byte 1 1 0 0 0 0 LB CB RB
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Byte 2 X7 X6 X5 X4 X3 X2 X1 X0
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Byte 3 Y7 Y6 Y5 Y4 Y3 Y4 Y1 Y0
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Byte 4 X7' X6' X5' X4' X3' X2' X1' X0'
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Byte 5 Y7' Y6' Y5' Y4' Y3' Y4' Y1' Y0'
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LB is left button state (0=pressed, 1=released)
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CB is center button state (0=pressed, 1=released)
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RB is right button state (0=pressed, 1=released)
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X7-X0 movement in X direction since last packet in signed byte
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format (-128..+127), positive direction right
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Y7-Y0 movement in Y direction since last packet in signed byte
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format (-128..+127), positive direction up
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X7'-X0' movement in X direction since sending of X7-X0 packet in signed byte
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format (-128..+127), positive direction right
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Y7'-Y0' movement in Y direction since sending of Y7-Y0 in signed byte
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format (-128..+127), positive direction up
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The last two bytes in the packet (bytes 4 and 5) contain information
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about movement data changes which have occured after data bytes 2 and
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3 have been sent.
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PS/2 mouse
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The standard PS/2 mouse (such as the Logitech mouse) defaults to 160 CPI
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and can be switched to 40, 80, 160 or 320 CPI via software. The Microsoft
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mouse driver for Windows 3.x and Windows 95 defaults to 160 counts per
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inch. The maximum tracking rate for PS/2 mouse is 40 reports/second *
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255 counts per report, or 10200 counts per second. A 100 CPI mouse could
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discriminate motion up to 102 inches per second while a 400 CPI mouse
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could discriminate motion up to 25.2 inches per second.
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Connector pinout
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Pin Wire Name
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1 DATA
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2 Reserved
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3 Ground
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4 +5V Supply
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5 CLK
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6 Reserved
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Shield Chassis
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Packet Format
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D7 D6 D5 D4 D3 D2 D1 D0
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Byte 1 XV XV YS XS 1 M R L
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Byte 2 X7 X6 X5 X4 X3 X2 X1 X0
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Byte 3 Y7 Y6 Y5 Y4 Y3 Y2 Y1 Y0
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L Left button state (1 = pressed down)
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M Middle button state (1 = pressed down)
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R Right button state (1 = pressed down)
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X0-X7 Movement in X direction
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Y0-Y7 Movement in Y direction
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XS,YS Movement data sign bits (1 = negative)
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XV,YV Movement data overflow bits (1 = overflow has occured)
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Physical connector
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The PS/2 mouse connector has the following pinout when looking at the
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connector on the back of the computer:
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4 u 6
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1 . 2
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3 5
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1. GND
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2. +5V
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3. DATA
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4. CLOCK
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5. Not used
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6. Not used
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Bi-directional transmission is controlled by the CLK and DATA lines. Both
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are fed by an open collector device which lets either host or mouse force
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the line to "0". During non-transmission, CLK is at "1" and DATA can be at
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"0" or "1".
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The host can inhibit mouse transmission by forcing CLK to "0". If the
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host inhibits the mouse while it is transmitting, the byte must be
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retransmitted (if the inhibit state arrived before the 11th clock).
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Receiving data: Check 'clock'. If inactive, there is a bit on the 'data'
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line. Each transmission unit is one start bit, eight data bits, odd
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parity and one stop bit. Start bits are low, stop bits high. Each clock
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active or inactive period is 30 to 50 microseconds. Data transition to
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falling edge of clock is 5 to 25 microseconds.
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Sending: Check that both clock and data are high. Pull down data for
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start bit, and start clocking.
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NOTE: Logitech has made the extension to this protocol to allow three
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buttons (the M bit is always 0 on 2 button mice).
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References
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* Original PC mouse info page by Tomi Engdahl
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http://www.hut.fi/~then/mytexts/mouse.html
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* PC Magazine May 28, 1991
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* Programmer's Reference to Genius Mouse
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ftp://x2ftp.oulu.fi/pub/msdos/programming/docs/gmouse.doc
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* Logitech Pointing Device Hardware Information Product Support Document # 1410
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ftp://ftp.logitech.com/pub/TechSupport/MOUSE/HELP/1410.txt
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* Mice: How do they work? by Richard Torrens
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http://box.argonet.co.uk/users/4qd/meece.html
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* In Pursuit Of The Perfect Portable Pointer by Intelink Electronics
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from EDN Products Edition April 16, 1977 pages 43-45
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* Programming the Microsoft Mouse
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http://www.geocities.com/SiliconValley/2151/mouse.html
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