153 lines
6 KiB
Text
153 lines
6 KiB
Text
Internal of HHKB pro
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=====================
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HHKB pro has MCU and some chips on separate two PCBs.
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Controller PCB
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--------------
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M38K07M4 Renesas MCU with USB function
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http://documentation.renesas.com/eng/products/mpumcu/rej03b0192_38k0ds.pdf
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(HHKB_controller.jpg)
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Keyswitch PCB
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-------------
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HC4051 Analog Multiplexer: select a row line.
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http://www.alldatasheet.com/datasheet-pdf/pdf/203989/KODENSHI/KK74HC4051A.html
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LS145 BCD Decoder: select a column line.
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http://www.alldatasheet.com/datasheet-pdf/pdf/27373/TI/SN74LS145D.html
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BU9831 Non-volatile electronic potentiometer: for calibration?
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http://www.alldatasheet.com/datasheet-pdf/pdf/36387/ROHM/BU9831.html
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TP1683/4 Capacitive Sensing controller: no datasheet available.
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(HHKB_keyswitch.jpg)
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Topre original chip?
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(HHKB_TP1684.jpg)
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Connector Cable
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---------------
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Two PCBs are connected by 15 lines(13 in case of Pro2).
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Vcc and GND use 3(2) lines each, other 9 lines are for keyboard signaling.
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Keyswitch connector
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pro pro2 Description Teensy++ pins
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--------------------------------------------------------------------------------------------
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1 Vcc(5V) Not exist on Pro2 5V
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2 1 Vcc(5V) 5V
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3 2 Vcc(5V) 5V
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4 3 TP1684 KEY: Low(0) when key pressed PE6 input(with pullup)
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5 4 TP1684 KEY_PREV: make threshold PE7 output
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6 5 HC4051 A(bit0)\ PB0 output
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7 6 HC4051 B(bit1) > select row(0 to 7) PB1 output
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8 7 HC4051 C(bit2)/ PB2 output
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9 8 LS145 A(bit0)\ PB3 output
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10 9 LS145 B(bit1) > select column(0 to 7) PB4 output
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11 10 LS145 C(bit2)/ PB5 output
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12 11 LS145 D(enable) Low(0) enables selected column PB6 output
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13 12 GND GND
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14 13 GND GND
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15 GND Not exist on Pro2 GND
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NOTE: guessing pin5(KEY_PREV) may work for hysteresis of capacitive sensing.
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NOTE: 1KOhm didn't work as pullup resistor on KEY. AVR internal pullup or 10KOhm resistor was OK.
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(HHKB_connector.jpg)
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Keyswitch matrix
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----------------
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60 keyswitches in 8*8 matrix. It is ghost-free and bounce-free.
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COL 0 1 2 3 4 5 6 7
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ROW ---------------------------------------------------------------
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0| 2 q w s a z x c
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1| 3 4 r e d f v b
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2| 5 6 y t g h n _NONE_
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3| 1 Esc Tab Control LShift LAlt LMeta Space
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4| 7 8 u i k j m _NONE_
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5| \ ` Delete Return Fn RShift RAlt RMeta
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6| 9 0 o p ; l , _NONE_
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7| - + ] [ ' / . _NONE_
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Matrix diagram:
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+-------------------------+-+-+-+-+-+-+-+ Vcc
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|bias control? - - - - - - - - ---
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| 3.9K*8 R R R R R R R R |
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+--------^+ +--------+ - - - - - - - - |
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| 2| | HC4051 <0-------|-|-|-|-|-|-|-|--|R|-+
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| |capa. | <1-------|-|-|-|-|-|-|-|--|R|-+
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| TP1684 |sense | <2-------|-|-|-|-|-|-|-|--|R|-+
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| 11<------| <3-------|-|-|-|-|-|-|-|--|R|-+
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| | | <4-------|-|-|-|-|-|-|-|--|R|-+
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| | | <5-------|-|-|-|-|-|-|-|--|R|-+
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| <-+ | <6-------|-|-|-|-|-|-|-|--|R|-+
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| 1 4 | | | <7-------|-|-|-|-|-|-|-|--|R|-+
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+---V---^-+ | +-^-^-^--+ 0 1 2 3 4 5 6 7 33K*8
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KEY PREV | A B C +-----------------+
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| | +-^----+ | | | | LS145 |
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Vcc | | |BU9831| | | | +-^--^--^--^------+
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--- | | +------+ | | | A B C D +------+
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| | | | | | | | | | | |
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1-3 4 5 6 7 8 9 10 11 12 13-15 |
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+--------------------------------------------------+ |
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| connector | ---
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+--------------------------------------------------+ GND
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to controller
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Signals charts
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--------------
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While pressing space bar, watched HHKB original controller signals by logic analyzer.
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Row and column is looping between 0-7 each for selecting a key.
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A key is scaned every about 15ms, so scan rate is 66Hz.
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(HHKB_chart1.jpg)
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Space bar locate at ROW:3 COL:7. A key is selected by HC4051(C,B,A) and LS145(C,B,A).
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Key state can be read on TP1684(4/KEY) while asserting low on LS145(D).
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Usage of TP1684(5) is not clear. Controller seemed to output previous key state on this line.
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However key state can be read without using this signal.
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(HHKB_chart2.jpg)
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Matrix scan pseudo code
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-----------------------
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for (row: 0-7) {
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SELECT_ROW(row); // set HC4051(A,B,C)
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for (col: 0-7) {
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SELECT_COL(col); // set LS145(A,B,C)
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_delay_us(40);
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if (prev_key_state(row, col)) {
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KEY_PREV_ON;
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}
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_delay_us(7);
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ENALBLE_COL(); // set LS145(D) to low
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_delay_us(10);
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if (KEY == 0) { // read TP1684(KEY)
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// key pressed
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} else {
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// not pressed
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}
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KEY_PREV_OFF;
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UNALBLE_COL(); // set LS145(D) to high
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_delay_us(150);
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}
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}
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EOF
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