In this project we will learn how to minimize the interfacing pin of 16×2 alphanumeric LCD with Arduino using PCF8574P ic.

PCF8574P ic: This IC is a silicon CMOS circuit. It provides general purpose I/O expansion for most of the microcontroller families via I2C bus. The device consists of an 8-bit quasi-bidirectional port and an I2C bus interface. The IC has low current consumption and includes latched outputs with high current drive capability.



A0 1 address input 0
A1 2 address input 1
A2 3 address input 2
P0 4 Quasi-bidirectional I/O 0
P1 5 Quasi-bidirectional I/O 1
P2 6 Quasi-bidirectional I/O 2
P3 7 Quasi-bidirectional I/O 3
VSS 8 Supply GRND
P4 9 Quasi-bidirectional I/O 4
P5 10 Quasi-bidirectional I/O 5
P6 11 Quasi-bidirectional I/O 6
P7 12 Quasi-bidirectional I/O 7
13 Interrupt output(LOW)
SCL 14 Serial clock line
SDA 15 Serial data line
VDD 16 Supply 5v

This project is built with Arduino UNO, 16×2 alphanumeric LCD and PCF8574P IC. This IC helps to convert two wire data communication into 8-bit data line and control lines.

This project works in the following manners:

  1. When you turn ON the system the library file for LCD imported and loaded in the Arduino.
  2. The system will start displaying character as per the code.


  • Power supply.
  • Arduino UNO
  • PCF8574P

16×2 alphanumeric LCD


According to the block diagram the controlling part is the Arduino UNO interfaces I2C based PCF8574P  IC with 16×2 alpha numeric LCD the circuit are attached to it are:

  1. Power supply
  2. PCF8574P IC
  3. 16×2 LCD

Power Supply: Here USB is used as the power supply from the computer.

PCF8574P and 16×2 LCD: Follow the table for the connection.

1 Address A0 To Ground pin
2 Address A1 To Ground pin
3 Address A2 To Ground pin
4 P0 11 –D4
5 P1 12 –D5
6 P2 13 –D6
7 P3 14 –D7
8 VSS To Ground pin
9 P4 6-EN
10 P5 5-RW
11 P6 4-RS
12 P7 Not connected
13 Not connected
14 SCL A-5 Arduino UNO
15 SDA A-4 Arduino UNO
16 VDD To Vcc-5v pin

How the Project Works:

A best written library function is available in the arduino.

It will start displaying automatically.


Search and Download code, circuit diagram from this LINK.