Tuesday, January 31, 2023

LCD 16×2 Pinout, Commands, and Displaying Custom Characters

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We come across Liquid Crystal Display (LCD) displays everywhere around us. Computers, calculators, television sets, mobile phones, and digital watches use some kind of display to display the time.

An LCD screen is an electronic display module that uses liquid crystal to produce a visible image. The 16×2 LCD display is a very basic module commonly used in DIYs and circuits. The 16×2 translates a display of 16 characters per line in 2 such lines. In this LCD, each character is displayed in a 5×7 pixel matrix.

16X2 LCD
LCD 16×2

LCD 16X2 Pinout Diagram

16x2 LCD Pinout
Pin Diagram

Pin No.

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 Function

 Name

1

Ground (0V)

Ground
2

Supply voltage; 5V (4.7V – 5.3V)

 Vcc

3

Contrast adjustment; the best way is to use a variable resistor such as a potentiometer. The output of the potentiometer is connected to this pin. Rotate the potentiometer knob forward and backward to adjust the LCD contrast.

 Vo / VEE

4 Selects command register when low, and data register when high RS (Register Select )
5 Low to write to the register; High to read from the register Read/write
6 Sends data to data pins when a high to low pulse is given; Extra voltage push is required to execute the instruction and EN(enable) signal is used for this purpose. Usually, we set en=0, when we want to execute the instruction we make it high en=1 for some milliseconds. After this we again make it ground that is, en=0. Enable
7 8-bit data pins DB0
8 DB1
9 DB2
10 DB3
11 DB4
12 DB5
13 DB6
14 DB7
15 LED Backlight VCC (5V) Led+
16 LED Backlight Ground (0V) Led-

RS (Register Select)

A 16X2 LCD has two registers, namely, command and data. The register select is used to switch from one register to other. RS=0 for the command register, whereas RS=1 for the data register.

Command Register: The command register stores the command instructions given to the LCD. A command is an instruction given to an LCD to do a predefined task. Examples like:

  • initializing it
  • clearing its screen
  • setting the cursor position
  • controlling display etc.

Processing for commands happens in the command register.

Data Register: The data register stores the data to be displayed on the LCD. The data is the ASCII value of the character to be displayed on the LCD. When we send data to LCD, it goes to the data register and is processed there. When RS=1, the data register is selected.

Important Command Codes for LCD

Sr.No. Hex Code Command to LCD instruction Register
1 01 Clear display screen
2 02 Return home
3 04 Decrement cursor (shift cursor to left)
4 06 Increment cursor (shift cursor to right)
5 05 Shift display right
6 07 Shift display left
7 08 Display off, cursor off
8 0A Display off, cursor on
9 0C Display on, cursor off
10 0E Display on, cursor blinking
11 0F Display on, cursor blinking
12 10 Shift cursor position to left
13 14 Shift the cursor position to the right
14 18 Shift the entire display to the left
15 1C Shift the entire display to the right
16 80 Force cursor to the beginning ( 1st line)
17 C0 Force cursor to the beginning ( 2nd line)
18 38 2 lines and 5×7 matrix

Displaying Custom Characters on 16X2 LCD

Generating custom characters on LCD is not very hard. It requires knowledge about the custom-generated random access memory (CG-RAM) of the LCD and the LCD chip controller. Most LCDs contain a Hitachi HD4478 controller.

CG-RAM is the main component in making custom characters. It stores the custom characters once declared in the code. CG-RAM size is 64 bytes providing the option of creating eight characters at a time. Each character is eight bytes in size.

CG-RAM address starts from 0x40 (Hexadecimal) or 64 in decimal. We can generate custom characters at these addresses. Once we generate our characters at these addresses, we can print them by just sending commands to the LCD. Character addresses and printing commands are below.

CG Ram Address and Commands
Table

In the table above you can see starting addresses for each character with their printing commands.

The first character is generated at addresses 0x40 to 0x47 and is printed on LCD by just sending a command 0.

The second character is generated at addresses 0x48 to 0x55 and is printed by sending a command 1.

How to Generate Custom Characters in CG-RAM

In LCD displays, each character is in a 5×8 matrix. Where 5 is the number of columns and 8 is the number of rows.

LCD 16x2 Matrix
LCD 16×2 Matrix

Here is a simple example of how to create the letter ‘b’ in CG-RAM.

The Array for generating ‘b’ is char b[7]={0x10,0x10,0x16,0x19,0x11,0x11,0x1E}; That is,

  • Send the address where you want to create a character.
  • Now create your character at this address. Send the ‘b’ character array values defined above one by one to the data register of the LCD.
  • To print the generated character at 0x40. Send command 0 to the command register of LCD. The table below would explain this more clearly-
Displaying Custom Characters on LCD 16x2
CG-RAM Address Table

Interfacing a 16X2 LCD with Arduino

LCD modules are very important in many Arduino-based embedded system designs to improve the user interface of the system. Interfacing with Arduino gives the programmer more freedom to customize the code easily. Any cost-effective Arduino board, a 16X2 character LCD display, jumper wires, and a breadboard are sufficient enough to build the circuit. The interfacing of Arduino to LCD display is below.

Interfacing LCD 16x2 with Arduino
Interfacing Circuit

Display the LED Brightness on a 16×2 LCD

The combination of an LCD and Arduino yields several projects, the most simple one being LCD to display the LED brightness. All we need for this circuit is an LCD, Arduino, breadboard, a resistor, potentiometer, LED, and some jumper cables. The circuit connections are below.

LCD 16x2 with Arduino Circuit Diagram
LCD 16×2 Project Circuit

The detailed project is available at displaying the brightness of a LED on an LCD display.


This article was first published on 21 November 2016 and recently updated on 08 December 2022.

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