-###V-USB circuit
- +---+ +---------------+
- USB GND | | ATmega168 |
- ~~~ C3 | |
- 5V <-------+--------+---|Vcc,AVCC | HHKB
- R1 | | ~~~~
- D- <----+--+-----R2-----|INT1 PB2-4|------->ROW(6-8)
- D+ <----|---+----R3-----|INT0 PC0-2|------->COL(9-11)
- Z1 Z2 | PC3|------->ENABLE(12)
- GND<----+---+-----------|GND PB0|<-------KEY(4)
- | PB1|------->PREV(5)
- | |
- GND+-C2--+--|XTAL1 RXD|------->Debug Console
- X1 | TXD|<-------Debug Console
- GND+-C3--+--|XTAL2 RST|---SW--+GND
- +---------------+
- R1: 1.5K Ohm
- R2,R3: 68 Ohm
- Z1,Z2: Zener 3.6V
- C1,C2: 22pF
- C3: 0.1uF
- X1: Crystal 20MHz(16MHz/12MHz)
- SW: Push Switch(Optional for bootloader)
+[dfu-programmer]: http://dfu-programmer.sourceforge.net/
+[FLIP]: http://www.atmel.com/tools/FLIP.aspx