forked from mirrors/qmk_firmware
135 lines
3.8 KiB
Text
135 lines
3.8 KiB
Text
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ADB Protocol
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============
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Resources
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---------
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Apple IIgs Hardware Reference Second Edition [p80(Chapter6 p121)]
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ftp://ftp.apple.asimov.net/pub/apple_II/documentation/Apple%20IIgs%20Hardware%20Reference.pdf
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ADB Keycode
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http://72.0.193.250/Documentation/macppc/adbkeycodes/
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http://m0115.web.fc2.com/m0115.jpg
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ADB Signaling
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http://kbdbabel.sourceforge.net/doc/kbd_signaling_pcxt_ps2_adb.pdf
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ADB Overview & History
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http://en.wikipedia.org/wiki/Apple_Desktop_Bus
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Microchip Application Note: ADB device(with code for PIC16C)
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http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1824&appnote=en011062
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AVR ATtiny2131 ADB to PS/2 converter(Japanese)
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http://hp.vector.co.jp/authors/VA000177/html/KeyBoardA5DEA5CBA5A2II.html
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Pinouts
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-------
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Female socket from the front
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4o o3
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2o o1
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==
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1: Data
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2: Power SW(low when press Power key)
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3: Vcc(5V)
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4: GND
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Commands
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--------
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ADB command is 1byte and consists of 4bit-address, 2bit-command
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type and 2bit-register. The commands are always sent by Host.
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Command format:
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7 6 5 4 3 2 1 0
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| | | |------------ address
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| |-------- command type
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| |---- register
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bits commands
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------------------------------------------------------
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- - - - 0 0 0 0 Send Request(reset all devices)
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A A A A 0 0 0 1 Flush(reset a device)
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- - - - 0 0 1 0 Reserved
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- - - - 0 0 1 1 Reserved
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- - - - 0 1 - - Reserved
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A A A A 1 0 R R Listen(write to a device)
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A A A A 1 1 R R Talk(read from a device)
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The command to read keycodes from keyboard is 0x2C which
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consist of keyboard address 2 and Talk against register 0.
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Address:
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2: keyboard
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3: mice
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Registers:
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0: application(keyobard/mice use to store its data.)
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1: application
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2: application
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3: status and command
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Communication
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-------------
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This is a minimum information for keyboard communication.
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See "Resources" for detail.
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Signaling:
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~~~~____________~~||||||||||||__~~~~~_~~|||||||||||||||__~~~~
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|800us | |7 Command 0| | | |15-64 Data 0|Stopbit(0)
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+Attention | | | +Startbit(1)
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+Startbit(1) | +Tlt(140-260us)
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+stopbit(0)
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Bit cells:
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bit0: ______~~~
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65 :35us
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bit1: ___~~~~~~
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35 :65us
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bit0 low time: 60-70% of bit cell(42-91us)
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bit1 low time: 30-40% of bit cell(21-52us)
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bit cell time: 70-130us
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[from Apple IIgs Hardware Reference Second Edition]
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Criterion for bit0/1:
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After 55us if line is low/high then bit is 0/1.
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Attention & start bit:
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Host asserts low in 560-1040us then places start bit(1).
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Tlt(Stop to Start):
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Bus stays high in 140-260us then device places start bit(1).
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Global reset:
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Host asserts low in 2.8-5.2ms. All devices are forced to reset.
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Send request from device(Srq):
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Device can request to send at commad(Global only?) stop bit.
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keep low for 300us to request.
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Keyboard data(register0)
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This 16bit data can contains 2 keycodes and 2 released flags.
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First keycode is palced in upper nibble. When one keyocode is sent,
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lower nibble is 0xFF.
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Release flag is 1 when key is released.
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15 14 . . . . . 8 7 6 . . . . . 0
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| |keycode1 | |keycode2
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|released(1) |released(1)
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Keycodes:
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Scancode consists of 7bit keycode and 1bit release flag.
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Device can send two keycodes at once. If just one keycode is sent
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keycode1 contains it and keyocode2 is 0xFF.
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Power switch:
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You can read the state from PSW line(active low) however
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the switch has a special scancode 0x7F7F, so you can
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also read from Data line. It uses 0xFFFF for release scancode.
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END_OF_ADB
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