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 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     Usage of TP1684(5) is not clear. Controller seemed to output previous key state on this line.
 175     However key state can be read without using this signal.
 176
 177     (HHKB_chart2.jpg)
 178
 179 5us after setting colA-C
 180 colA   _~~~~~~~~~~~~~~~~~~
 181 prev    _~~~~_____          20us if previous key state is low
 182 colD    ~~~__~~~~~          10us column enabled
 183 key     ~~~____~~~          22us hold state of the key
 184
 185 prev    ____~~~~__________  20us(JP)/17us(Pro2)
 186 key     ~~~~~~_____~~~~~~~  22us
 187 colD    ~~~~~~__~~~~~~~~~~  10us(LS175)
 188
 189 colC    ____~~~~____~~~~    550/410us(JP)
 190 colB    __~~__~~__~~__~~    200/210us(JP)
 191 colA    _~_~_~_~_~_~_~_~    100/110us(JP)   200/210us(Pro2)
 192         0123456701234567    selected column
 193
 194 rowC    ____~~~~____~~~~    3.8/3.8ms(JP)   S2 of HC4051
 195 rowB    __~~__~~__~~__~~    1.9/1.9ms(JP)   S1 of HC4051
 196 rowA    _~_~_~_~_~_~_~_~    1.0/1.0ms(JP)   S0 of HC4051
 197         0123456701234567    selected row(Pro/Pro2)
 198         0123456789ABCDEF    selected row(JP)
 199 rowEn0  ________~~~~~~~~    7.7/7.7ms   ~Enable of Z2 HC4051(JP only)
 200 rowEn1  ~~~~~~~~________    7.7/7.7ms   ~Enable of Z3 HC4051(JP only)
 201
 202 NOTE: JP scans twice fast as Pro2 does. So Pro2 scan 8x8 matrix in 15.4ms while JP can 16x8 in that time.
 203
 204
 205
 206
 207 Matrix scan pseudo code
 208 -----------------------
 209     for (row: 0-7) {
 210         SELECT_ROW(row);        // set HC4051(A,B,C)
 211
 212         for (col: 0-7) {
 213             SELECT_COL(col);    // set LS145(A,B,C)
 214
 215             _delay_us(40);
 216
 217             if (prev_key_state(row, col)) {
 218                 KEY_PREV_ON;
 219             }
 220
 221             _delay_us(7);
 222
 223             ENALBLE_COL();      // set LS145(D) to low
 224
 225             _delay_us(10);
 226
 227             if (KEY == 0) {     // read TP1684(KEY)
 228                 // key pressed
 229             } else {
 230                 // not pressed
 231             }
 232
 233             KEY_PREV_OFF;
 234             UNALBLE_COL();      // set LS145(D) to high
 235
 236             _delay_us(150);
 237         }
 238     }
 239
 240
 241
 242 EOF