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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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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.ti.com/lit/ds/schs122j/schs122j.pdf
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LS145 BCD Decoder: select a column line.
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http://www.ti.com/lit/ds/symlink/sn74ls145.pdf
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BU9831 Non-volatile electronic potentiometer: for calibration?
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https://www.spezial.com/doc/rohm-a/bu9831.pdf
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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 lines are for keyboard signaling.
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HHKB connector lines:
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JP Pro2 Pro Function Description Teensy++ pins
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--------------------------------------------------------------------------------------------
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1 Vcc(5V) 5V
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1 1 2 Vcc(5V) 5V
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2 2 3 Vcc(5V) 5V
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3 3 4 TP1684 KEY: Low(0) when key pressed PE6 input(with pullup)
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4 4 5 TP1684 KEY_PREV: make threshold PE7 output
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5 5 6 HC4051 A(bit0)\ PB0 output
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6 6 7 HC4051 B(bit1) > select row 0-7 PB1 output
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7 7 8 HC4051 C(bit2)/ PB2 output
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8 8 9 LS145 A(bit0)\ PB3 output
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9 9 10 LS145 B(bit1) > select column 0-7 PB4 output
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10 10 11 LS145 C(bit2)/ PB5 output
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11 11 12 LS145 D(enable) Low(0) enables selected column PB6 output
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12 12 13 GND GND
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13 13 14 GND GND
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15 GND
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14 HC4051(Z2) ~Enable of Z2 row0-7
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15 HC4051(Z3) ~Enable of Z3 row8-15
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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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NOTE: JP has two HC4051(Z2,Z3) and line 5, 6 and 7 are connected to both of them.
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(HHKB_connector.jpg)
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Keyswitch matrix
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----------------
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HHKB switch matrix is ghost-free and bounce-free.
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Pro/Pro2(8x8):
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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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JP(16x8):
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COL 0 1 2 3 4 5 6 7
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ROW ---------------------------------------------------------------
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0| ESC TAB LFn LShift LCtrl
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1| 4 E MuHKN C D
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2| 3 W LAlt X S
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3| 1 HHK
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4|
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5| 5 R V F
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6| 2 Q LGui Z A
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7| 6 T Space B G
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8| 9 I Kana , K
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9| 8 U Henkan M J
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A| 7 Y N H
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B| 0 O RAlt . L
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C| BS Right RShift Enter
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D| \ [ Down Up ]
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E| - P RFn / ;
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F| ~ @ Left Ro :
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Matrix diagram:
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Pro/Pro2:
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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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1-3 4 5 6 7 8 9 10 11 12 13-15 Pro |
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1-2 3 4 5 6 7 8 9 10 11 12-13 Pro2|
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+--------------------------------------------------+ |
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| connector | ---
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+--------------------------------------------------+ GND
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JP:
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+-----------------------------+-+-+-+-+ Vcc
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|bias control? - - - - - ---
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| 3.9K*5 R R R R R |
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+--------^+ +--------+ - - - - - |
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| | | HC4051 <0-----------|-|-|-|-|----|R|-+
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| |capa. | Z2 <1-----------|-|-|-|-|----|R|-+
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| TP1684 |sense | <2-----------|-|-|-|-|----|R|-+
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| <---+--| <3-----------|-|-|-|-|----|R|-+
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| | | | <4-----------|-|-|-|-|----|R|-+
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| | ~En| <5-----------|-|-|-|-|----|R|-+
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| | +----> <6-----------|-|-|-|-|----|R|-+
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| | | | | A B C <7-----------|-|-|-|-|----|R|-+
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+---V---^-+ | | +-^-^-^--+ | | | | | |
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KEY PREV | | | | | | | | | | |
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| | | | +--------+ | | | | | |
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| | | | | HC4051 <8-----------|-|-|-|-|----|R|-+
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| | | | | Z3 <9-----------|-|-|-|-|----|R|-+
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| | | +--| <A-----------|-|-|-|-|----|R|-+
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| | | | <B-----------|-|-|-|-|----|R|-+
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| | | | <C-----------|-|-|-|-|----|R|-+
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| | | ~En| <D-----------|-|-|-|-|----|R|-+
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| | | +-> <E-----------|-|-|-|-|----|R|-+
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| | | | | A B C <F-----------|-|-|-|-|----|R|-+
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| | | | +-^-^-^--+ 0 1 2 3 4 5 6 7 33K*8
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| | | | | | | +-----------------+
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| | | | | | | | LS145 |
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Vcc | | | | | | | +-^--^--^--^------+
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--- | | | | | | | A B C D +-------+
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1-2 3 4 14 15 5 6 7 8 9 10 11 12-13 |
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+--------------------------------------------------+ |
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| connector | ---
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+--------------------------------------------------+ GND
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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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5us after setting colA-C
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colA _~~~~~~~~~~~~~~~~~~
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prev _~~~~_____ 20us if previous key state is low
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colD ~~~__~~~~~ 10us column enabled
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key ~~~____~~~ 22us hold state of the key
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prev ____~~~~__________ 20us(JP)/17us(Pro2)
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key ~~~~~~_____~~~~~~~ 22us
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colD ~~~~~~__~~~~~~~~~~ 10us(LS175)
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colC ____~~~~____~~~~ 550/410us(JP)
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colB __~~__~~__~~__~~ 200/210us(JP)
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colA _~_~_~_~_~_~_~_~ 100/110us(JP) 200/210us(Pro2)
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0123456701234567 selected column
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rowC ____~~~~____~~~~ 3.8/3.8ms(JP) S2 of HC4051
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rowB __~~__~~__~~__~~ 1.9/1.9ms(JP) S1 of HC4051
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rowA _~_~_~_~_~_~_~_~ 1.0/1.0ms(JP) S0 of HC4051
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0123456701234567 selected row(Pro/Pro2)
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0123456789ABCDEF selected row(JP)
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rowEn0 ________~~~~~~~~ 7.7/7.7ms ~Enable of Z2 HC4051(JP only)
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rowEn1 ~~~~~~~~________ 7.7/7.7ms ~Enable of Z3 HC4051(JP only)
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NOTE: JP scans twice fast as Pro2 does. So Pro2 scan 8x8 matrix in 15.4ms while JP can 16x8 in that time.
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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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