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                               Teensy++ pins
  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 pressed              PE6 input(with pullup)
  40      4    4      5      TP1684      KEY_PREV: make threshold                  PE7 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
  52     15                  HC4051(Z3)  ~Enable of Z3   row8-15
  53
  54     NOTE: guessing pin5(KEY_PREV) may work for hysteresis of capacitive sensing.
  55     NOTE: 1KOhm didn't work as pullup resistor on KEY. AVR internal pullup or 10KOhm resistor was OK.
  56     NOTE: JP has two HC4051(Z2,Z3) and line 5, 6 and 7 are connected to both of them.
  57
  58     (HHKB_connector.jpg)
  59
  60
  61 Keyswitch matrix
  62 ----------------
  63 HHKB switch matrix is ghost-free and bounce-free.
  64
  65     Pro/Pro2(8x8):
  66       COL 0     1       2       3       4       5       6       7
  67     ROW ---------------------------------------------------------------
  68       0|  2     q       w       s       a       z       x       c
  69       1|  3     4       r       e       d       f       v       b
  70       2|  5     6       y       t       g       h       n       _NONE_
  71       3|  1     Esc     Tab     Control LShift  LAlt    LMeta   Space
  72       4|  7     8       u       i       k       j       m       _NONE_
  73       5|  \     `       Delete  Return  Fn      RShift  RAlt    RMeta
  74       6|  9     0       o       p       ;       l       ,       _NONE_
  75       7|  -     +       ]       [       '       /       .       _NONE_
  76
  77
  78     JP(16x8):
  79       COL 0     1       2       3       4       5       6       7
  80     ROW ---------------------------------------------------------------
  81       0|                ESC     TAB     LFn     LShift  LCtrl
  82       1|                4       E       MuHKN   C       D
  83       2|                3       W       LAlt    X       S
  84       3|                1               HHK
  85       4|
  86       5|                5       R               V       F
  87       6|                2       Q       LGui    Z       A
  88       7|                6       T       Space   B       G
  89       8|                9       I       Kana    ,       K
  90       9|                8       U       Henkan  M       J
  91       A|                7       Y               N       H
  92       B|                0       O       RAlt    .       L
  93       C|                BS              Right   RShift  Enter
  94       D|                \       [       Down    Up      ]
  95       E|                -       P       RFn     /       ;
  96       F|                ~       @       Left    Ro      :
  97
  98
  99 Matrix diagram:
 100
 101     Pro/Pro2:
 102              +-------------------------+-+-+-+-+-+-+-+     Vcc
 103              |bias control?            - - - - - - - -     ---
 104              |                  3.9K*8 R R R R R R R R      |
 105     +--------^+      +--------+        - - - - - - - -      |
 106     |        2|      | HC4051 <0-------|-|-|-|-|-|-|-|--|R|-+
 107     |         |capa. |        <1-------|-|-|-|-|-|-|-|--|R|-+
 108     | TP1684  |sense |        <2-------|-|-|-|-|-|-|-|--|R|-+
 109     |       11<------|        <3-------|-|-|-|-|-|-|-|--|R|-+
 110     |         |      |        <4-------|-|-|-|-|-|-|-|--|R|-+
 111     |         |      |        <5-------|-|-|-|-|-|-|-|--|R|-+
 112     |         <-+    |        <6-------|-|-|-|-|-|-|-|--|R|-+
 113     |   1   4 | |    |        <7-------|-|-|-|-|-|-|-|--|R|-+
 114     +---V---^-+ |    +-^-^-^--+        0 1 2 3 4 5 6 7  33K*8
 115        KEY PREV |      A B C         +-----------------+
 116         |   | +-^----+ | | |         |      LS145      |
 117     Vcc |   | |BU9831| | | |         +-^--^--^--^------+
 118     --- |   | +------+ | | |           A  B  C  D   +-------+
 119      |  |   |          | | |           |  |  |  |   |       |
 120     1-3 4   5          6 7 8           9 10 11 12 13-15 Pro |
 121     1-2 3   4          5 6 7           8  9 10 11 12-13 Pro2|
 122     +--------------------------------------------------+    |
 123     |                connector                         |   ---
 124     +--------------------------------------------------+   GND
 125
 126
 127     JP:
 128              +-----------------------------+-+-+-+-+       Vcc
 129              |bias control?                - - - - -       ---
 130              |                  3.9K*5     R R R R R        |
 131     +--------^+      +--------+            - - - - -        |
 132     |         |      | HC4051 <0-----------|-|-|-|-|----|R|-+
 133     |         |capa. |    Z2  <1-----------|-|-|-|-|----|R|-+
 134     | TP1684  |sense |        <2-----------|-|-|-|-|----|R|-+
 135     |         <---+--|        <3-----------|-|-|-|-|----|R|-+
 136     |         |   |  |        <4-----------|-|-|-|-|----|R|-+
 137     |         |   ~En|        <5-----------|-|-|-|-|----|R|-+
 138     |         | +---->        <6-----------|-|-|-|-|----|R|-+
 139     |         | | |  | A B C  <7-----------|-|-|-|-|----|R|-+
 140     +---V---^-+ | |  +-^-^-^--+            | | | | |        |
 141        KEY PREV | |    | | |               | | | | |        |
 142         |   |   | |  +--------+            | | | | |        |
 143         |   |   | |  | HC4051 <8-----------|-|-|-|-|----|R|-+
 144         |   |   | |  |    Z3  <9-----------|-|-|-|-|----|R|-+
 145         |   |   | +--|        <A-----------|-|-|-|-|----|R|-+
 146         |   |   |    |        <B-----------|-|-|-|-|----|R|-+
 147         |   |   |    |        <C-----------|-|-|-|-|----|R|-+
 148         |   |   | ~En|        <D-----------|-|-|-|-|----|R|-+
 149         |   |   |  +->        <E-----------|-|-|-|-|----|R|-+
 150         |   |   |  | | A B C  <F-----------|-|-|-|-|----|R|-+
 151         |   |   |  | +-^-^-^--+        0 1 2 3 4 5 6 7  33K*8
 152         |   |   |  |   | | |         +-----------------+
 153         |   |   |  |   | | |         |      LS145      |
 154     Vcc |   |   |  |   | | |         +-^--^--^--^------+
 155     --- |   |   |  |   | | |           A  B  C  D   +-------+
 156      |  |   |   |  |   | | |           |  |  |  |   |       |
 157     1-2 3   4  14 15   5 6 7           8  9 10 11 12-13     |
 158     +--------------------------------------------------+    |
 159     |                connector                         |   ---
 160     +--------------------------------------------------+   GND
 161
 162
 163 Signals charts
 164 --------------
 165     While pressing space bar, watched HHKB Pro original controller signals by logic analyzer.
 166     Row and column is looping between 0-7 each for selecting a key.
 167     A key is scaned every about 15ms, so scan rate is 66Hz.
 168
 169     (HHKB_chart1.jpg)
 170
 171     Space bar locate at ROW:3 COL:7. A key is selected by HC4051(C,B,A) and LS145(C,B,A).
 172     Key state can be read on TP1684(4/KEY) while asserting low on LS145(D).
 173
 174     (HHKB_chart2.jpg)
 175
 176
 177     Signal of JP:
 178
 179     1) Select row
 180     rowC    ____~~~~____~~~~    3.8/3.8ms(JP) 7.7/7.7ms(Pro)   S2 of HC4051
 181     rowB    __~~__~~__~~__~~    1.9/1.9ms(JP) 3.8/3.8ms(Pro)   S1 of HC4051
 182     rowA    _~_~_~_~_~_~_~_~    1.0/1.0ms(JP) 1.9/1.9ms(Pro)   S0 of HC4051
 183             0123456701234567    selected row(Pro)
 184             0123456789ABCDEF    selected row(JP)
 185     rowEn0  ________~~~~~~~~    7.7/7.7ms(JP only)              ~Enable of Z2 HC4051(JP only)
 186     rowEn1  ~~~~~~~~________    7.7/7.7ms(JP only)              ~Enable of Z3 HC4051(JP only)
 187
 188     2) Select column
 189     colC    ____~~~~____~~~~    550/410us(JP)      /   us(Pro)
 190     colB    __~~__~~__~~__~~    200/210us(JP)   450/460us(Pro)
 191     colA    _~_~_~_~_~_~_~_~    100/110us(JP)   220/230us(Pro)
 192             0123456701234567    selected column
 193
 194     3) Wait 5us after column select, then set prev, strobe colD to spit out key status and read it.
 195     prev    _~~~~_____          20us if previous key state is low
 196     colD    ~~~__~~~~~          10us strobe
 197     key     ~~~____~~~          22us indicates current state of the key
 198
 199     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.
 200
 201
 202
 203 EOF