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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 Teensy++ pins
--------------------------------------------------------------------------------------------
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 pressed PE6 input(with pullup)
4 4 5 TP1684 KEY_PREV: make threshold PE7 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
15 HC4051(Z3) ~Enable of Z3 row8-15
NOTE: guessing pin5(KEY_PREV) may work for hysteresis of capacitive sensing.
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 PREV | 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 PREV | | | | | | | | | | |
| | | | +--------+ | | | | | |
| | | | | 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.
prev _~~~~_____ 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
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