What is 16x2 Parallel LCD ?

1. Introduction

A 16x2 LCD display refers to a Liquid Crystal Display module with 16 columns and 2 rows of characters, also available in multiple combinations of 18x4, etc. Each character space can display a single alphanumeric character, symbol, or custom character. The display operates by selectively controlling the liquid crystal pixels, making them opaque or transparent to create characters or graphics.

2. Pin Configuration

3. Hardware description

There are 16 pins available in most cases constate of power, data, and control.

• VSS: Ground (0V)
• VDD: Power supply (+5V)
• VEE: Contrast adjustment voltage (can be used to control the display contrast)
• RS: Register Select (0 for command input, 1 for data input)
• RW: Read/Write (0 for write, 1 for read)
• E: Enable (Used to enable the data or command)
• D0-D7: Data lines (8-bit parallel data lines used to send information)
• A: Anode (backlight anode, usually connected to +5V through a current-limiting resistor)
• K: Cathode (backlight cathode, connected to ground)

4. Working Principle

The 16x2 LCD display works by manipulating the liquid crystal to form characters or graphics. When a voltage is applied to the liquid crystal, it changes its molecular alignment, affecting light polarization and making it either transparent or opaque. The display controller takes the data and generates the signals required to control the liquid crystals and display the characters or graphics on the screen.

5. Modes of LCD

LCD works on 2 main different modes 4-bit mode and 8-bit mode 

• 4-bit Mode
  In the 4-bit mode, data is sent to the LCD module in two consecutive nibbles. The higher nibble, consisting of data lines D4 to D7, is sent first, followed by the lower nibble with data lines D0 to D3. This configuration enables us to send 8-bit data using only four data lines, conserving valuable I/O pins on the microcontroller.
• 8-bit Mode
  In the 8-bit mode, the LCD can directly receive 8-bit data in a single transmission, using all eight data lines (D0 to D7). As a result, this mode offers faster and more efficient data transfer compared to the 4-bit mode. However, it requires more I/O pins on the microcontroller, potentially limiting its application in projects with limited available pins.

6. LCD Commands:

LCD requires some commands and instructions to show output on the screen and the set of commands is provided by the microcontroller to the LCD, let's discuss some of the commonly used commands 

• Clear Display (0x01): This command clears the entire display, resetting the cursor position to the home position (0, 0).
• Return Home (0x02): Sending this command moves the cursor to the home position (0, 0) without clearing the display.
• Entry Mode Set (0x04): This command determines the cursor movement direction and whether the display should shift or not.
• Display On/Off Control (0x08): This command controls the display, cursor, and cursor blinking options.
• Cursor or Display Shift (0x10): Used to shift the cursor or the entire display left or right without changing the display data.
• Function Set (0x20): This command sets the LCD data length (4-bit or 8-bit), number of display lines, and font size.
• Set CGRAM Address (0x40): This command sets the address of the Character Generator RAM (CGRAM) for custom character creation.
• Set DDRAM Address (0x80): This command sets the address of the Display Data RAM (DDRAM), allowing data to be written to a specific location on the LCD.
  

7. Applications

16x2 LCD is used for a wide range of projects and industrial purpose 
1. Embedded systems:- these displays serve as user interfaces, providing status updates, menu navigation, and interaction options.
2. Home automation:- LCD displays can be used to show temperature, humidity, and other sensor readings in home automation projects.