Low Cost 1 Wire Lcd for 8 Pin Micro Controllers [romanblack Shift1 System ]

Shift1 System is a cheap and simple way to get lots of digital output pins and only needs 1 PIC pin to drive it.

Step 1: How It Works - the Simple System

Normally, serial-in parallel-out shift register ICs can be set up for 2 pin operation;

DAT - data, is the next bit to be shifted in
CLK - clock pulse, on / edge the next bit is shifted in

This can be "cheated" to just use one pin and timed-length pulse. An RC network is used to provide a time delay for the DAT line to change. Very short pulses mean that a 1 bit is shifted in. With a long enough pulse the DAT voltage drops low enough so that a 0 bit is shifted in when the CLK line goes / again.

Step 2: Shift1 LATCHED System for Driving LCDs

reference link : http://www.romanblack.com/shift1.htm

Step 3: Circuit Diagram

1, 74hc595    - 1
2, 1.5 k resistor -1
3, 33 k resistor - 1
4,   0.1uf polyster capacitor -1
5, 2.2nf non capacitor - 2
6, 220 ohm resistor -1
7, 2n7000 mosfet -1
8 ,5K preset -   1    ,for lcd contrast adjust
9, button switch - lcd back light ON/OFF [optional ]
10, pic12f675