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 ]
Step 4: Vero Board Assembling
Step 5: Test Board – Pic12F675 Micro Development Board [3.0 Cm X 2.5 Cm Size]
Step 6: Finished Circuit Board
Step 7: Working Video
special thanks to roman black.