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
- TP1684 Capacitive Sensing controller: no datasheet available.
+ TP1683/4 Capacitive Sensing controller: no datasheet available.
(HHKB_keyswitch.jpg)
|bias control? - - - - - - - - ---
| 3.9K*8 R R R R R R R R |
+--------^+ +--------+ - - - - - - - - |
- | TP 1684 | | HC4051 <0-------|-|-|-|-|-|-|-|--|R|-+
+ | 2| | HC4051 <0-------|-|-|-|-|-|-|-|--|R|-+
| |capa. | <1-------|-|-|-|-|-|-|-|--|R|-+
- | |sense | <2-------|-|-|-|-|-|-|-|--|R|-+
- | <------| <3-------|-|-|-|-|-|-|-|--|R|-+
+ | TP1684 |sense | <2-------|-|-|-|-|-|-|-|--|R|-+
+ | 11<------| <3-------|-|-|-|-|-|-|-|--|R|-+
| | | <4-------|-|-|-|-|-|-|-|--|R|-+
| | | <5-------|-|-|-|-|-|-|-|--|R|-+
- | |calib.| <6-------|-|-|-|-|-|-|-|--|R|-+
- | <-+? | <7-------|-|-|-|-|-|-|-|--|R|-+
- +---V-----+ | +-^-^-^--+ 0 1 2 3 4 5 6 7 33K*8
- KEY ??? | A B C +-----------------+
+ | <-+ | <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 +------+