Author: admin

In this Instructable you are going to see how to connect i2c lcd display to arduino and how to print on lcd display.

Each I2C bus consists of two signals: SCL and SDA. SCL is the clock signal, and SDA is the data signal. The clock signal is always generated by the current bus master; some slave devices may force the clock low at times to delay the master sending more data (or to require more time to prepare data before the master attempts to clock it out). This is called “clock stretching” and is described on the protocol page.

To connect 16×2 LCD display to Arduino we use i2c PCF 8574T module. This module expands Arduino pins and allow connection of display using only two Arduino pins.

I2C module has four pins: GND – ground, VCC – 5V power, SDA – data signal, SCL – clock signal. Connect SDA to A4 pin on Arduino, and SCL to A5 pin:

GND <---> GND
VCC <---> 5V
SDA <---> A4
SCL <---> A5

For working with display on Arduino we need two libraries: Wire.h, LiquidCrystal_I2C.h.

Wire.h is standard Arduino IDE library, and LiquidCrystal_I2C.h is the library for work with LCD displays. You can download it from official Arduino project website: https://www.arduino.cc/reference/en/libraries/liquidcrystal-i2c/

And here is the source code of simple sketch, which write text on 16×2 LCD display:

#include <Wire.h>
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27,16,2);

void setup() 
{
  lcd.init();
  lcd.backlight();

  lcd.setCursor(0,0); // set cursor to 1 symbol of 1 line
  lcd.print("Arduino Lessons:");

  lcd.setCursor(0,1); // set cursor to 1 symbol of 2 line
  lcd.print("www.andjey.info"); 
}

void loop() 
{  

}

Let’s write simple program, that will turn on and off LED on our Arduino. For our lesson we need: Arduino, one LED diode, USB cable for programming our Arduino, PC with Arduino IDE, download it you can here: https://www.arduino.cc/en/software

Connect USB cable to Arduino, for connecting LED we will use D13 pin and GND PIN (see Arduino Nano pins here). Positive wire of diode connect to D13, negative wire – to Ground pin as you can see on photo:

In Arduino IDE create new blank project:

Here You can see two functions: setup() – which run when Arduion power on, and function loop() – which run in cycle all type when arduino is working. Now let’s create our program.

Bewore function start() let’s create two constants – it will be basic configuration of our program. BLINK_PIN defines which pin is used for connecting LED. BLINK_TIME – define time in milliseconds how long our LED will be on and off.

#define BLINK_PIN 13
#define BLINK_TIME 1000

In function setup() configure pin 13 as output pin:

void setup() {
  pinMode(BLINK_PIN,1);
}

Now create function blink_led() – that will turn on and off our LED:

void blink_led()
{
  digitalWrite(BLINK_PIN, 1);
  delay(BLINK_TIME);
  
  digitalWrite(BLINK_PIN, 0);
  delay(BLINK_TIME);
}

Now write function blink_led() in loop() to run our program in cycle all time when Arduino works:

void loop() {
  blink_led();
}

Full code of program:

#define BLINK_PIN 13
#define BLINK_TIME 300

void blink_led()
{
  digitalWrite(BLINK_PIN, 1);
  delay(BLINK_TIME);
  
  digitalWrite(BLINK_PIN, 0);
  delay(BLINK_TIME);
}

void setup() {
  pinMode(BLINK_PIN,1);
}

void loop() {
  blink_led();
}

Now save program and compile it to your Arduino:

Arduino has 14 digital PIN for digital devices and 8 analog PIN for analog devices. Here is detail information about all Arduino Nano pins: