keychron_qmk_firmware/keyboard/hhkb/doc/HHKB.txt

Internal of HHKB pro
=====================
HHKB pro has MCU and some chips on separate two PCBs.

Controller PCB
--------------
    M38K07M4    Renesas MCU with USB function
                http://documentation.renesas.com/eng/products/mpumcu/rej03b0192_38k0ds.pdf

    (HHKB_controller.jpg)

Keyswitch PCB
-------------
    HC4051      Analog Multiplexer: select a row line.
                http://www.ti.com/lit/ds/schs122j/schs122j.pdf
    LS145       BCD Decoder: select a column line.
                http://www.ti.com/lit/ds/symlink/sn74ls145.pdf
    BU9831      Non-volatile electronic potentiometer: for calibration?
                https://www.spezial.com/doc/rohm-a/bu9831.pdf
    TP1683/4    Capacitive Sensing controller: no datasheet available.

    (HHKB_keyswitch.jpg)

    Topre original chip?
    (HHKB_TP1684.jpg)


Connector Cable
---------------
Two PCBs are connected by 15 lines(13 in case of Pro2).
Vcc and GND use 3(2) lines each, other lines are for keyboard signaling.

    HHKB connector lines:
    JP   Pro2   Pro     Function    Description                               TMK pin usage
    --------------------------------------------------------------------------------------------
                 1      Vcc(5V)                                               5V
     1    1      2      Vcc(5V)                                               5V
     2    2      3      Vcc(5V)                                               5V
     3    3      4      TP1684      ~KEY: Low(0) when key is pressed          PD7 input(with pullup)
     4    4      5      TP1684      HYS: High(1) when key is pressed          PB7 output
     5    5      6      HC4051      A(bit0)\                                  PB0 output
     6    6      7      HC4051      B(bit1) > select row 0-7                  PB1 output
     7    7      8      HC4051      C(bit2)/                                  PB2 output
     8    8      9      LS145       A(bit0)\                                  PB3 output
     9    9     10      LS145       B(bit1) > select column 0-7               PB4 output
    10   10     11      LS145       C(bit2)/                                  PB5 output
    11   11     12      LS145       ~D(enable) Low(0) enables selected column PB6 output
    12   12     13      GND                                                   GND
    13   13     14      GND                                                   GND
                15      GND
    14                  HC4051(Z2)  ~Enable of Z2   row0-7                    PC6
    15                  HC4051(Z3)  ~Enable of Z3   row8-15                   PC7

    NOTE: Probably HYS changes threshold for upstroke and makes hysteresis in the result.
    NOTE: HYS should be given High(1) when previous KEY state is Low(0).
    NOTE: 1KOhm didn't work as pullup resistor on KEY. AVR internal pullup or 10KOhm resistor was OK.
    NOTE: JP has two HC4051(Z2,Z3) and line 5, 6 and 7 are connected to both of them.

    (HHKB_connector.jpg)


Keyswitch matrix
----------------
HHKB switch matrix is ghost-free and bounce-free.

    Pro/Pro2(8x8):
      COL 0     1       2       3       4       5       6       7
    ROW ---------------------------------------------------------------
      0|  2     q       w       s       a       z       x       c
      1|  3     4       r       e       d       f       v       b
      2|  5     6       y       t       g       h       n       _NONE_
      3|  1     Esc     Tab     Control LShift  LAlt    LMeta   Space
      4|  7     8       u       i       k       j       m       _NONE_
      5|  \     `       Delete  Return  Fn      RShift  RAlt    RMeta
      6|  9     0       o       p       ;       l       ,       _NONE_
      7|  -     +       ]       [       '       /       .       _NONE_


    JP(16x8):
      COL 0     1       2       3       4       5       6       7
    ROW ---------------------------------------------------------------
      0|                ESC     TAB     LFn     LShift  LCtrl
      1|                4       E       MuHKN   C       D
      2|                3       W       LAlt    X       S
      3|                1               HHK
      4|  
      5|                5       R               V       F
      6|                2       Q       LGui    Z       A
      7|                6       T       Space   B       G
      8|                9       I       Kana    ,       K
      9|                8       U       Henkan  M       J
      A|                7       Y               N       H
      B|                0       O       RAlt    .       L
      C|                BS              Right   RShift  Enter
      D|                \       [       Down    Up      ]
      E|                -       P       RFn     /       ;
      F|                ~       @       Left    Ro      :


Matrix diagram:

    Pro/Pro2:
             +-------------------------+-+-+-+-+-+-+-+     Vcc
             |bias control?            - - - - - - - -     ---
             |                  3.9K*8 R R R R R R R R      |
    +--------^+      +--------+        - - - - - - - -      |  
    |        2|      | HC4051 <0-------|-|-|-|-|-|-|-|--|R|-+
    |         |capa. |        <1-------|-|-|-|-|-|-|-|--|R|-+
    | TP1684  |sense |        <2-------|-|-|-|-|-|-|-|--|R|-+
    |       11<------|        <3-------|-|-|-|-|-|-|-|--|R|-+
    |         |      |        <4-------|-|-|-|-|-|-|-|--|R|-+
    |         |      |        <5-------|-|-|-|-|-|-|-|--|R|-+
    |         <-+    |        <6-------|-|-|-|-|-|-|-|--|R|-+
    |   1   4 | |    |        <7-------|-|-|-|-|-|-|-|--|R|-+
    +---V---^-+ |    +-^-^-^--+        0 1 2 3 4 5 6 7  33K*8
       KEY HYS  |      A B C         +-----------------+
        |   | +-^----+ | | |         |      LS145      |
    Vcc |   | |BU9831| | | |         +-^--^--^--^------+
    --- |   | +------+ | | |           A  B  C  D   +-------+
     |  |   |          | | |           |  |  |  |   |       |
    1-3 4   5          6 7 8           9 10 11 12 13-15 Pro |
    1-2 3   4          5 6 7           8  9 10 11 12-13 Pro2|
    +--------------------------------------------------+    |
    |                connector                         |   ---
    +--------------------------------------------------+   GND


    JP:
             +-----------------------------+-+-+-+-+       Vcc
             |bias control?                - - - - -       ---
             |                  3.9K*5     R R R R R        |
    +--------^+      +--------+            - - - - -        |  
    |         |      | HC4051 <0-----------|-|-|-|-|----|R|-+
    |         |capa. |    Z2  <1-----------|-|-|-|-|----|R|-+
    | TP1684  |sense |        <2-----------|-|-|-|-|----|R|-+
    |         <---+--|        <3-----------|-|-|-|-|----|R|-+
    |         |   |  |        <4-----------|-|-|-|-|----|R|-+
    |         |   ~En|        <5-----------|-|-|-|-|----|R|-+
    |         | +---->        <6-----------|-|-|-|-|----|R|-+
    |         | | |  | A B C  <7-----------|-|-|-|-|----|R|-+
    +---V---^-+ | |  +-^-^-^--+            | | | | |        |
       KEY HYS  | |    | | |               | | | | |        |
        |   |   | |  +--------+            | | | | |        |
        |   |   | |  | HC4051 <8-----------|-|-|-|-|----|R|-+
        |   |   | |  |    Z3  <9-----------|-|-|-|-|----|R|-+
        |   |   | +--|        <A-----------|-|-|-|-|----|R|-+
        |   |   |    |        <B-----------|-|-|-|-|----|R|-+
        |   |   |    |        <C-----------|-|-|-|-|----|R|-+
        |   |   | ~En|        <D-----------|-|-|-|-|----|R|-+
        |   |   |  +->        <E-----------|-|-|-|-|----|R|-+
        |   |   |  | | A B C  <F-----------|-|-|-|-|----|R|-+
        |   |   |  | +-^-^-^--+        0 1 2 3 4 5 6 7  33K*8
        |   |   |  |   | | |         +-----------------+
        |   |   |  |   | | |         |      LS145      |
    Vcc |   |   |  |   | | |         +-^--^--^--^------+
    --- |   |   |  |   | | |           A  B  C  D   +-------+
     |  |   |   |  |   | | |           |  |  |  |   |       |
    1-2 3   4  14 15   5 6 7           8  9 10 11 12-13     |
    +--------------------------------------------------+    |
    |                connector                         |   ---
    +--------------------------------------------------+   GND
                                    

Signals charts
--------------
    While pressing space bar, watched HHKB Pro original controller signals by logic analyzer.
    Row and column is looping between 0-7 each for selecting a key.
    A key is scaned every about 15ms, so scan rate is 66Hz.

    (HHKB_chart1.jpg)

    Space bar locate at ROW:3 COL:7. A key is selected by HC4051(C,B,A) and LS145(C,B,A).
    Key state can be read on TP1684(4/KEY) while asserting low on LS145(D). 

    (HHKB_chart2.jpg)


    Signal of JP:

    1) Select row
    rowC    ____~~~~____~~~~    3.8/3.8ms(JP) 7.7/7.7ms(Pro)   S2 of HC4051
    rowB    __~~__~~__~~__~~    1.9/1.9ms(JP) 3.8/3.8ms(Pro)   S1 of HC4051
    rowA    _~_~_~_~_~_~_~_~    1.0/1.0ms(JP) 1.9/1.9ms(Pro)   S0 of HC4051
            0123456701234567    selected row(Pro)
            0123456789ABCDEF    selected row(JP)
    rowEn0  ________~~~~~~~~    7.7/7.7ms(JP only)              ~Enable of Z2 HC4051(JP only)
    rowEn1  ~~~~~~~~________    7.7/7.7ms(JP only)              ~Enable of Z3 HC4051(JP only)

    2) Select column
    colC    ____~~~~____~~~~    550/410us(JP)      /   us(Pro)
    colB    __~~__~~__~~__~~    200/210us(JP)   450/460us(Pro)
    colA    _~_~_~_~_~_~_~_~    100/110us(JP)   220/230us(Pro)
            0123456701234567    selected column

    3) Wait 5us after column select, then set prev, strobe colD to spit out key status and read it.
    hys     _~~~~_____          20us if previous key state is low
    colD    ~~~__~~~~~          10us strobe
    key     ~~~____~~~          22us indicates current state of the key

    NOTE: JP scans twice fast as Pro/Pro2 does. So Pro/Pro2 scans 8x8 matrix in 15.4ms while JP scans 16x8 in that time.



EOF