4 x 4 keyboard

GSM-like keyboard

Below: Connector on 515/535-mainboard.
Box-header 20 connections.

PCF8574A (70h)
LCD-display		 PCF8574A (72h)
Keyboard
P0 P2 P4 P6 GND +5 V P0 P2 P4 P6
P1 P3 P5 P7 GND +5 V P1 P3 P5 P7

Below: Connection PCF8574A (address 70h and 72h) on 515/535-mainboard to LCD-display and keyboard

LCD-display

Keyboard 4 x 4
P0 DB4 P0 Row0
P1 DB5 P1 Row1
P2 DB6 P2 Row2
P3 DB7 P3 Row3
P4 RS P4 Column0
P5 R/W P5 Column1
P6 NC P6 Column2
P7 E P7 Column3