Liquid Crystal Displays (LCDs), particularly the 16x2 LCD, are fundamental components in the world of electronics, frequently used in a wide range of applications from basic microcontroller projects to complex industrial instruments.
By defining custom character patterns, we can extend the LCD's display capabilities beyond standard characters.
The AT89C51 microcontroller from the 8051 family, with its robust architecture and versatile features, provides an excellent platform for driving these displays. This article delves into the creation of custom characters and animations on a 16x2 LCD using the AT89C51, offering a blend of both technical insight and practical guidance.
16x2 LCD
The 16x2 LCD, which displays 16 characters per line with 2 such lines, operates on the principle of controlling liquid crystals to modulate light. Each character on the LCD is formed by a 5x8 matrix of pixels, allowing for the display of standard ASCII characters and custom-designed graphics.
Technical Specifications
Display Size
16 characters, 2 lines
Character Matrix
5x8 pixels per character
Interface
Usually a 4-bit or 8-bit digital interface
Supply Voltage
Typically 5V
The AT89C51 Microcontroller
The AT89C51 is a powerful yet cost-effective microcontroller from the 8051 family, known for its simplicity and ease of use. It features 4KB of Flash programmable and erasable read-only memory (PEROM) and 128 bytes of RAM, making it suitable for controlling LCDs.
Key Features
CPU
8-bit microcontroller
Memory
4KB Flash, 128 bytes RAM
I/O Ports
Four 8-bit ports, P0 through P3
Clock Speed
Up to 12 MHz
Interfacing the 16x2 LCD with AT89C51
Interfacing a 16x2 LCD with the AT89C51 involves connecting the data and control lines of the LCD to the I/O ports of the microcontroller.
The data lines (D0-D7) can be connected directly to an 8-bit port for an 8-bit interface or to the higher half (D4-D7) for a 4-bit interface.
Control lines include Register Select (RS), Read/Write (R/W), and Enable (E).
Creating Custom Characters
Custom characters are created by defining a 5x8 pixel matrix, where each pixel can be either on or off. This matrix is then stored in the LCD's Character Generator RAM (CGRAM).
Steps to Create Custom Characters
Define the Character
Create a binary representation of the character. Each byte represents a row of the character matrix.
Set CGRAM Address
Send a command to the LCD to set the starting address of the CGRAM where the custom character will be stored.
Write Character Data
Write the binary data for each row of the character to the CGRAM.
Programming the AT89C51 for Custom Characters
To program the AT89C51, a software development environment like Keil µVision can be used. The program should initialize the LCD, define the custom characters, and display them on the screen.
// Pseudocode for initializing LCD and defining custom characters
LCD_Init(); // Initialize LCD
// Define custom character
unsigned char customChar[8] = {0x04, 0x0E, 0x0E, 0x0E, 0x1F, 0x00, 0x00, 0x00};
// Load custom character into CGRAM
LCD_CustomChar(0, customChar); // Load character at CGRAM location 0
// Display custom character
LCD_Cmd(0x80); // Set cursor position
LCD_Write_Char(0); // Write custom character from CGRAM location 0
Animations on the LCD
Animations on the 16x2 LCD can be created by sequentially displaying custom characters or manipulating standard characters to simulate motion. This requires careful timing and character manipulation to create the illusion of movement.
Steps to Create Animations
Design the Animation Frames
Create each frame of the animation as a series of custom characters.
Sequential Display
Rapidly display these frames in sequence to create the animation.
Control Timing
Use delay functions to control the speed of the animation.
Creating custom characters and animations on a 16x2 LCD using the AT89C51 microcontroller is a fascinating way to add visual appeal to electronic projects.
It demonstrates the versatility of basic components like LCDs and microcontrollers, encouraging creativity and innovation in embedded system design.
With the combination of custom characters and animation techniques, the possibilities for enhancing the visual appeal of a 16x2 LCD are vast. From displaying intricate symbols to creating captivating animations, this tutorial will guide you through the steps necessary to achieve engaging results with the AT89C51 microcontroller.