Three Wire LCD Interface with Arduino

We have seen parallel interface technique using Arduino library and we know that it requires 6 IO Lines, Now let’s see how we can reduce required IO’s using 74HC595. We know that we can reduce number IO required by using I2C based LCD interface circuit; It costs ten times more than 74HC595 Circuit.

Arduino 3 wire LCD interface circuit

            In this circuit similar to the bargraph display we are using 74HC595 Shift register to interface 16×2 LCD.

3 Wire LCD Interface with Arduino Circuit
3 Wire LCD Interface with Arduino Circuit

For LCD contrast setting 1K Ohm fixed resistor is used it gives optimum contrast value. Connect R/W to ground as we are not going to read the LCD. LCD is connected in 4-bit mode.

Arduino Code for 3 wire LCD

Here we are not using any library to interface the LCD.

Result

This technique saves IO lines as well as circuit cost.

 

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