Chapter 20 LCD1602

In this chapter, we will learn about the LCD1602 Display Screen.

Project 20.1 LCD1602

In this section we learn how to use LCD1602 to display something.

Component List

ESP8266 x1	USB cable
Breadboard x1
LCD1602 Module x1	Jumper wire F/M x6

Component knowledge

I2C communication

I2C (Inter-Integrated Circuit) is a two-wire serial communication mode, which can be used for the connection of micro controllers and their peripheral equipment. Devices using I2C communication must be connected to the serial data (SDA) line, and serial clock (SCL) line (called I2C bus). Each device has a unique address and can be used as a transmitter or receiver to communicate with devices connected to the bus.

LCD1602 communication’

The LCD1602 display screen can display 2 lines of characters in 16 columns. It is capable of displaying numbers, letters, symbols, ASCII code and so on. As shown below is a monochrome LCD1602 display screen along with its circuit pin diagram.

I2C LCD1602 display screen integrates a I2C interface, which connects the serial-input & parallel-output module to the LCD1602 display screen. This allows us to only use 4 lines to the operate the LCD1602.

The serial-to-parallel IC chip used in this module is PCF8574T (PCF8574AT), and its default I2C address is 0x27(0x3F).

Below is the PCF8574 pin schematic diagram and the block pin diagram:

PCF8574 chip pin diagram:	PCF8574 chip pin diagram:

PCF8574 module pin and LCD1602 pin are corresponding to each other and connected with each other:

So we only need 4 pins to control the 16 pins of the LCD1602 display screen through the I2C interface.

In this project, we will use the I2C LCD1602 to display some static characters and dynamic variables.

Circuit

Schematic diagram

Hardware connection If you need any support, please feel free to contact us via: support@freenove.com

Sketch

How to install the library

We use the third party library LiquidCrystal I2C. If you haven’t installed it yet, please do so before learning. The steps to add third-party Libraries are as follows: open arduino->Sketch->Include library-> Manage libraries. Enter “ LiquidCrystal I2C” in the search bar and select “ LiquidCrystal I2C “ for installation.

Use I2C LCD 1602 to display characters and variables.

Sketch_20.1_Display_the_string_on_LCD1602

Compile and upload the code to ESP8266 and the LCD1602 displays characters.

The following is the program code:

/**********************************************************************
  Filename    : Drive LiquidCrystal I2C to display characters
  Description : I2C is used to control the display characters of LCD1602.
  Auther      : www.freenove.com
  Modification: 2020/07/11
**********************************************************************/
#include <LiquidCrystal_I2C.h>
#include <Wire.h>

#define SDA 13                    //Define SDA pins
#define SCL 14                    //Define SCL pins

/*
 * note:If lcd1602 uses PCF8574T, IIC's address is 0x27,
 *      or lcd1602 uses PCF8574AT, IIC's address is 0x3F.
*/
LiquidCrystal_I2C lcd(0x27,16,2); 
void setup() {
  Wire.begin(SDA, SCL);           // attach the IIC pin
  if (!i2CAddrTest(0x27)) {
    lcd = LiquidCrystal_I2C(0x3F, 16, 2);
  }
  lcd.init();                     // LCD driver initialization
  lcd.backlight();                // Open the backlight
  lcd.setCursor(0,0);             // Move the cursor to row 0, column 0
  lcd.print("hello, world!");     // The print content is displayed on the LCD
}

void loop() {
  lcd.setCursor(0,1);             // Move the cursor to row 1, column 0
  lcd.print("Counter:");          // The count is displayed every second
  lcd.print(millis() / 1000);
  delay(1000);
}

bool i2CAddrTest(uint8_t addr) {
  Wire.begin();
  Wire.beginTransmission(addr);
  if (Wire.endTransmission() == 0) {
    return true;
  }
  return false;
}

Include header file of Liquid Crystal Display (LCD)1602 and I2C.

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

Instantiate the I2C LCD1602 screen. It should be noted here that if your LCD driver chip uses PCF8574T, set the I2C address to 0x27, and if uses PCF8574AT, set the I2C address to 0x3F.

LiquidCrystal_I2C lcd(0x27,16,2); 

Initialize I2C and set its pins as 13,14. And then initialize LCD1602 and turn on the backlight of LCD.

Wire.begin(SDA, SCL);           // attach the IIC pin
lcd.init();                     // LCD driver initialization
lcd.backlight();                // Turn on the backlight

Move the cursor to the first row, first column, and then display the character.

lcd.setCursor(0,0);             // Move the cursor to row 0, column 0
lcd.print("hello, world!");     // The print content is displayed on the LCD

Print the number on the second line of LCD1602.

void loop() {
  lcd.setCursor(0,1);             // Move the cursor to row 1, column 0
  lcd.print("Counter:");          // The count is displayed every second
  lcd.print(millis() / 1000);
  delay(1000);
}

Reference

class LiquidCrystal

The LiquidCrystal class can manipulate common LCD screens. The first step is defining an object of

LiquidCrystal, for example:

LiquidCrystal_I2C lcd(0x27,16,2);

Instantiate the Lcd1602 and set the I2C address to 0x27, with 16 columns per row and 2 rows per column.

init();

Initializes the Lcd1602’s device

backlight();

Turn on Lcd1602’s backlight.

setCursor(column,row);

Sets the screen’s column and row.

column: The range is 0 to 15.

row: The range is 0 to 1.

print(String);

Print the character string on Lcd1602