keyboard/hhkb/doc/HHKB.txt

   1 Internal of HHKB pro
   2 =====================
   3 HHKB pro has MCU and some chips on separate two PCBs.
   4
   5 Controller PCB
   6 --------------
   7     M38K07M4    Renesas MCU with USB function
   8                 http://documentation.renesas.com/eng/products/mpumcu/rej03b0192_38k0ds.pdf
   9
  10     (HHKB_controller.jpg)
  11
  12 Keyswitch PCB
  13 -------------
  14     HC4051      Analog Multiplexer: select a row line.
  15                 http://www.ti.com/lit/ds/schs122j/schs122j.pdf
  16     LS145       BCD Decoder: select a column line.
  17                 http://www.ti.com/lit/ds/symlink/sn74ls145.pdf
  18     BU9831      Non-volatile electronic potentiometer: for calibration?
  19                 https://www.spezial.com/doc/rohm-a/bu9831.pdf
  20     TP1683/4    Capacitive Sensing controller: no datasheet available.
  21
  22     (HHKB_keyswitch.jpg)
  23
  24     Topre original chip?
  25     (HHKB_TP1684.jpg)
  26
  27
  28 Connector Cable
  29 ---------------
  30 Two PCBs are connected by 15 lines(13 in case of Pro2).
  31 Vcc and GND use 3(2) lines each, other lines are for keyboard signaling.
  32
  33     HHKB connector lines:
  34     JP   Pro2   Pro     Function    Description                               TMK pin usage
  35     --------------------------------------------------------------------------------------------
  36                  1      Vcc(5V)                                               5V
  37      1    1      2      Vcc(5V)                                               5V
  38      2    2      3      Vcc(5V)                                               5V
  39      3    3      4      TP1684      ~KEY: Low(0) when key is pressed          PD7 input(with pullup)
  40      4    4      5      TP1684      HYS: High(1) when key is pressed          PB7 output
  41      5    5      6      HC4051      A(bit0)\                                  PB0 output
  42      6    6      7      HC4051      B(bit1) > select row 0-7                  PB1 output
  43      7    7      8      HC4051      C(bit2)/                                  PB2 output
  44      8    8      9      LS145       A(bit0)\                                  PB3 output
  45      9    9     10      LS145       B(bit1) > select column 0-7               PB4 output
  46     10   10     11      LS145       C(bit2)/                                  PB5 output
  47     11   11     12      LS145       ~D(enable) Low(0) enables selected column PB6 output
  48     12   12     13      GND                                                   GND
  49     13   13     14      GND                                                   GND
  50                 15      GND
  51     14                  HC4051(Z2)  ~Enable of Z2   row0-7                    PC6
  52     15                  HC4051(Z3)  ~Enable of Z3   row8-15                   PC7
  53
  54     NOTE: Probably HYS changes threshold for upstroke and makes hysteresis in the result.
  55     NOTE: HYS should be given High(1) when previous KEY state is Low(0).
  56     NOTE: 1KOhm didn't work as pullup resistor on KEY. AVR internal pullup or 10KOhm resistor was OK.
  57     NOTE: JP has two HC4051(Z2,Z3) and line 5, 6 and 7 are connected to both of them.
  58
  59     (HHKB_connector.jpg)
  60
  61
  62 Keyswitch matrix
  63 ----------------
  64 HHKB switch matrix is ghost-free and bounce-free.
  65
  66     Pro/Pro2(8x8):
  67       COL 0     1       2       3       4       5       6       7
  68     ROW ---------------------------------------------------------------
  69       0|  2     q       w       s       a       z       x       c
  70       1|  3     4       r       e       d       f       v       b
  71       2|  5     6       y       t       g       h       n       _NONE_
  72       3|  1     Esc     Tab     Control LShift  LAlt    LMeta   Space
  73       4|  7     8       u       i       k       j       m       _NONE_
  74       5|  \     `       Delete  Return  Fn      RShift  RAlt    RMeta
  75       6|  9     0       o       p       ;       l       ,       _NONE_
  76       7|  -     +       ]       [       '       /       .       _NONE_
  77
  78
  79     JP(16x8):
  80       COL 0     1       2       3       4       5       6       7
  81     ROW ---------------------------------------------------------------
  82       0|                ESC     TAB     LFn     LShift  LCtrl
  83       1|                4       E       MuHKN   C       D
  84       2|                3       W       LAlt    X       S
  85       3|                1               HHK
  86       4|
  87       5|                5       R               V       F
  88       6|                2       Q       LGui    Z       A
  89       7|                6       T       Space   B       G
  90       8|                9       I       Kana    ,       K
  91       9|                8       U       Henkan  M       J
  92       A|                7       Y               N       H
  93       B|                0       O       RAlt    .       L
  94       C|                BS              Right   RShift  Enter
  95       D|                \       [       Down    Up      ]
  96       E|                -       P       RFn     /       ;
  97       F|                ~       @       Left    Ro      :
  98
  99
 100 Matrix diagram:
 101
 102     Pro/Pro2:
 103              +-------------------------+-+-+-+-+-+-+-+     Vcc
 104              |bias control?            - - - - - - - -     ---
 105              |                  3.9K*8 R R R R R R R R      |
 106     +--------^+      +--------+        - - - - - - - -      |
 107     |        2|      | HC4051 <0-------|-|-|-|-|-|-|-|--|R|-+
 108     |         |capa. |        <1-------|-|-|-|-|-|-|-|--|R|-+
 109     | TP1684  |sense |        <2-------|-|-|-|-|-|-|-|--|R|-+
 110     |       11<------|        <3-------|-|-|-|-|-|-|-|--|R|-+
 111     |         |      |        <4-------|-|-|-|-|-|-|-|--|R|-+
 112     |         |      |        <5-------|-|-|-|-|-|-|-|--|R|-+
 113     |         <-+    |        <6-------|-|-|-|-|-|-|-|--|R|-+
 114     |   1   4 | |    |        <7-------|-|-|-|-|-|-|-|--|R|-+
 115     +---V---^-+ |    +-^-^-^--+        0 1 2 3 4 5 6 7  33K*8
 116        KEY HYS  |      A B C         +-----------------+
 117         |   | +-^----+ | | |         |      LS145      |
 118     Vcc |   | |BU9831| | | |         +-^--^--^--^------+
 119     --- |   | +------+ | | |           A  B  C  D   +-------+
 120      |  |   |          | | |           |  |  |  |   |       |
 121     1-3 4   5          6 7 8           9 10 11 12 13-15 Pro |
 122     1-2 3   4          5 6 7           8  9 10 11 12-13 Pro2|
 123     +--------------------------------------------------+    |
 124     |                connector                         |   ---
 125     +--------------------------------------------------+   GND
 126
 127
 128     JP:
 129              +-----------------------------+-+-+-+-+       Vcc
 130              |bias control?                - - - - -       ---
 131              |                  3.9K*5     R R R R R        |
 132     +--------^+      +--------+            - - - - -        |
 133     |         |      | HC4051 <0-----------|-|-|-|-|----|R|-+
 134     |         |capa. |    Z2  <1-----------|-|-|-|-|----|R|-+
 135     | TP1684  |sense |        <2-----------|-|-|-|-|----|R|-+
 136     |         <---+--|        <3-----------|-|-|-|-|----|R|-+
 137     |         |   |  |        <4-----------|-|-|-|-|----|R|-+
 138     |         |   ~En|        <5-----------|-|-|-|-|----|R|-+
 139     |         | +---->        <6-----------|-|-|-|-|----|R|-+
 140     |         | | |  | A B C  <7-----------|-|-|-|-|----|R|-+
 141     +---V---^-+ | |  +-^-^-^--+            | | | | |        |
 142        KEY HYS  | |    | | |               | | | | |        |
 143         |   |   | |  +--------+            | | | | |        |
 144         |   |   | |  | HC4051 <8-----------|-|-|-|-|----|R|-+
 145         |   |   | |  |    Z3  <9-----------|-|-|-|-|----|R|-+
 146         |   |   | +--|        <A-----------|-|-|-|-|----|R|-+
 147         |   |   |    |        <B-----------|-|-|-|-|----|R|-+
 148         |   |   |    |        <C-----------|-|-|-|-|----|R|-+
 149         |   |   | ~En|        <D-----------|-|-|-|-|----|R|-+
 150         |   |   |  +->        <E-----------|-|-|-|-|----|R|-+
 151         |   |   |  | | A B C  <F-----------|-|-|-|-|----|R|-+
 152         |   |   |  | +-^-^-^--+        0 1 2 3 4 5 6 7  33K*8
 153         |   |   |  |   | | |         +-----------------+
 154         |   |   |  |   | | |         |      LS145      |
 155     Vcc |   |   |  |   | | |         +-^--^--^--^------+
 156     --- |   |   |  |   | | |           A  B  C  D   +-------+
 157      |  |   |   |  |   | | |           |  |  |  |   |       |
 158     1-2 3   4  14 15   5 6 7           8  9 10 11 12-13     |
 159     +--------------------------------------------------+    |
 160     |                connector                         |   ---
 161     +--------------------------------------------------+   GND
 162
 163
 164 Signals charts
 165 --------------
 166     While pressing space bar, watched HHKB Pro original controller signals by logic analyzer.
 167     Row and column is looping between 0-7 each for selecting a key.
 168     A key is scaned every about 15ms, so scan rate is 66Hz.
 169
 170     (HHKB_chart1.jpg)
 171
 172     Space bar locate at ROW:3 COL:7. A key is selected by HC4051(C,B,A) and LS145(C,B,A).
 173     Key state can be read on TP1684(4/KEY) while asserting low on LS145(D).
 174
 175     (HHKB_chart2.jpg)
 176
 177
 178     Signal of JP:
 179
 180     1) Select row
 181     rowC    ____~~~~____~~~~    3.8/3.8ms(JP) 7.7/7.7ms(Pro)   S2 of HC4051
 182     rowB    __~~__~~__~~__~~    1.9/1.9ms(JP) 3.8/3.8ms(Pro)   S1 of HC4051
 183     rowA    _~_~_~_~_~_~_~_~    1.0/1.0ms(JP) 1.9/1.9ms(Pro)   S0 of HC4051
 184             0123456701234567    selected row(Pro)
 185             0123456789ABCDEF    selected row(JP)
 186     rowEn0  ________~~~~~~~~    7.7/7.7ms(JP only)              ~Enable of Z2 HC4051(JP only)
 187     rowEn1  ~~~~~~~~________    7.7/7.7ms(JP only)              ~Enable of Z3 HC4051(JP only)
 188
 189     2) Select column
 190     colC    ____~~~~____~~~~    550/410us(JP)      /   us(Pro)
 191     colB    __~~__~~__~~__~~    200/210us(JP)   450/460us(Pro)
 192     colA    _~_~_~_~_~_~_~_~    100/110us(JP)   220/230us(Pro)
 193             0123456701234567    selected column
 194
 195     3) Wait 5us after column select, then set prev, strobe colD to spit out key status and read it.
 196     hys     _~~~~_____          20us if previous key state is low
 197     colD    ~~~__~~~~~          10us strobe
 198     key     ~~~____~~~          22us indicates current state of the key
 199
 200     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.
 201
 202
 203
 204 EOF