# Documentation 
## 1.0 Keypad
The kepad is driven by an io-expander. Thus it can be acessed over i2c.
Adress 0x21
### 1.1 Wiring
* Red: 3.3V
* Black GND
* Green SDA -> D3
* Grey SCL -> D4  

## 2.0 LCD
The LCD display is driven on the same i2c bus as the keypad.

nterface Definition
BYTE BIT
7 (MSB) 6 5 4 3 2 1 0 (LSB)
I2C slave address L H L L A2 A1 A0 R/W
I/O data bus P7 P6 P5 P4 P3 P2 P1 P0