Vcc and GND use 3(2) lines each, other lines are for keyboard signaling.
HHKB connector lines:
- JP Pro2 Pro Function Description Teensy++ pins
+ JP Pro2 Pro Function Description TMK pin usage
--------------------------------------------------------------------------------------------
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
+ 3 3 4 TP1684 ~KEY: Low(0) when key is pressed PD7 input(with pullup)
+ 4 4 5 TP1684 HYS: High(1) when key is pressed PB7 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
+ 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
+ 14 HC4051(Z2) ~Enable of Z2 row0-7 PC6
+ 15 HC4051(Z3) ~Enable of Z3 row8-15 PC7
- NOTE: guessing pin5(KEY_PREV) may work for hysteresis of capacitive sensing.
+ NOTE: Probably HYS changes threshold for upstroke and makes hysteresis in the result.
+ NOTE: HYS should be given High(1) when previous KEY state is Low(0).
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.
| <-+ | <6-------|-|-|-|-|-|-|-|--|R|-+
| 1 4 | | | <7-------|-|-|-|-|-|-|-|--|R|-+
+---V---^-+ | +-^-^-^--+ 0 1 2 3 4 5 6 7 33K*8
- KEY PREV | A B C +-----------------+
+ KEY HYS | A B C +-----------------+
| | +-^----+ | | | | LS145 |
Vcc | | |BU9831| | | | +-^--^--^--^------+
--- | | +------+ | | | A B C D +-------+
| | +----> <6-----------|-|-|-|-|----|R|-+
| | | | | A B C <7-----------|-|-|-|-|----|R|-+
+---V---^-+ | | +-^-^-^--+ | | | | | |
- KEY PREV | | | | | | | | | | |
+ KEY HYS | | | | | | | | | | |
| | | | +--------+ | | | | | |
| | | | | HC4051 <8-----------|-|-|-|-|----|R|-+
| | | | | Z3 <9-----------|-|-|-|-|----|R|-+
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
+ hys _~~~~_____ 20us if previous key state is low
colD ~~~__~~~~~ 10us strobe
key ~~~____~~~ 22us indicates current state of the key