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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.alldatasheet.com/datasheet-pdf/pdf/203989/KODENSHI/KK74HC4051A.html
- LS145 BCD Decoder: select a column line.
- http://www.alldatasheet.com/datasheet-pdf/pdf/27373/TI/SN74LS145D.html
- BU9831 Non-volatile electronic potentiometer: for calibration?
- http://www.alldatasheet.com/datasheet-pdf/pdf/36387/ROHM/BU9831.html
- 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 9 lines are for keyboard signaling.
-
- Keyswitch connector
- pro pro2 Description Teensy++ pins
- --------------------------------------------------------------------------------------------
- 1 Vcc(5V) Not exist on Pro2 5V
- 2 1 Vcc(5V) 5V
- 3 2 Vcc(5V) 5V
- 4 3 TP1684 KEY: Low(0) when key pressed PE6 input(with pullup)
- 5 4 TP1684 KEY_PREV: make threshold PE7 output
- 6 5 HC4051 A(bit0)\ PB0 output
- 7 6 HC4051 B(bit1) > select row(0 to 7) PB1 output
- 8 7 HC4051 C(bit2)/ PB2 output
- 9 8 LS145 A(bit0)\ PB3 output
- 10 9 LS145 B(bit1) > select column(0 to 7) PB4 output
- 11 10 LS145 C(bit2)/ PB5 output
- 12 11 LS145 D(enable) Low(0) enables selected column PB6 output
- 13 12 GND GND
- 14 13 GND GND
- 15 GND Not exist on Pro2 GND
-
- 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.
-
- (HHKB_connector.jpg)
-
-
- Keyswitch matrix
- ----------------
- 60 keyswitches in 8*8 matrix. It is ghost-free and bounce-free.
-
- 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_
-
-
- Matrix diagram:
-
- +-------------------------+-+-+-+-+-+-+-+ 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 |
- +--------------------------------------------------+ |
- | connector | ---
- +--------------------------------------------------+ GND
- to controller
-
-
- Signals charts
- --------------
- While pressing space bar, watched HHKB 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).
-
- Usage of TP1684(5) is not clear. Controller seemed to output previous key state on this line.
- However key state can be read without using this signal.
-
- (HHKB_chart2.jpg)
-
-
- Matrix scan pseudo code
- -----------------------
- for (row: 0-7) {
- SELECT_ROW(row); // set HC4051(A,B,C)
-
- for (col: 0-7) {
- SELECT_COL(col); // set LS145(A,B,C)
-
- _delay_us(40);
-
- if (prev_key_state(row, col)) {
- KEY_PREV_ON;
- }
-
- _delay_us(7);
-
- ENALBLE_COL(); // set LS145(D) to low
-
- _delay_us(10);
-
- if (KEY == 0) { // read TP1684(KEY)
- // key pressed
- } else {
- // not pressed
- }
-
- KEY_PREV_OFF;
- UNALBLE_COL(); // set LS145(D) to high
-
- _delay_us(150);
- }
- }
-
-
-
- EOF
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