Power-electronicsHow-ToBeginner · 3 min read

How to Scroll Text on LCD in Embedded C: Simple Guide

To scroll text on an LCD in embedded C, display a substring of the full text on the LCD and update the starting position in a timed loop. Use lcd_clear() and lcd_set_cursor() functions to refresh the display with the next part of the text, creating a scrolling effect.

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Syntax

To scroll text on an LCD, you typically use these steps:

lcd_clear(): Clears the LCD screen.
lcd_set_cursor(row, column): Moves the cursor to the specified position.
lcd_print(string): Prints the string starting at the cursor.
Use a loop to change the starting index of the substring to display.

This creates the illusion of scrolling by shifting the visible part of the text.

embedded_c

void scroll_text(char *text, int lcd_width) {
    int len = strlen(text);
    for (int i = 0; i <= len - lcd_width; i++) {
        lcd_clear();
        lcd_set_cursor(0, 0);
        lcd_print(&text[i]);
        delay(300); // wait to see the scroll
    }
}

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Example

This example scrolls a long message on a 16-character LCD line by showing parts of the string one by one.

embedded_c

#include <string.h>
#include <stdio.h>

// Mock LCD functions for demonstration
void lcd_clear() {
    printf("\033[2J\033[H"); // Clear terminal screen
}

void lcd_set_cursor(int row, int col) {
    // For simplicity, ignore cursor positioning in this demo
}

void lcd_print(const char *str) {
    printf("%.*s\n", 16, str); // Print max 16 chars
}

void delay(int ms) {
    // Simple delay loop (not accurate)
    for (volatile long i = 0; i < ms * 1000; i++);
}

void scroll_text(const char *text, int lcd_width) {
    int len = strlen(text);
    if (len <= lcd_width) {
        lcd_clear();
        lcd_set_cursor(0, 0);
        lcd_print(text);
        return;
    }
    for (int i = 0; i <= len - lcd_width; i++) {
        lcd_clear();
        lcd_set_cursor(0, 0);
        lcd_print(&text[i]);
        delay(300);
    }
}

int main() {
    const char *message = "Hello, this is scrolling text on LCD!";
    scroll_text(message, 16);
    return 0;
}

Output

Hello, this is sc ello, this is scr llo, this is scro lo, this is scrol o, this is scroll , this is scrolli this is scrollin this is scrolling his is scrolling is is scrolling t s is scrolling te is scrolling tex is scrolling text s scrolling text scrolling text o scrolling text on crolling text on rolling text on L olling text on LC lling text on LCD ling text on LCD!

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Common Pitfalls

Common mistakes when scrolling text on LCD include:

Not clearing the LCD before printing new text, causing overlapping characters.
Not handling text shorter than the LCD width, which can cause unexpected behavior.
Using delays that are too short or too long, making the scroll too fast or too slow.
Not resetting the cursor position before printing.

embedded_c

/* Wrong way: No lcd_clear and no cursor reset */
lcd_print(&text[i]); // Overlapping text

/* Right way: Clear and set cursor before printing */
lcd_clear();
lcd_set_cursor(0, 0);
lcd_print(&text[i]);

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Quick Reference

Tips for smooth LCD text scrolling:

Always clear the display before printing new text.
Set the cursor to the start position before printing.
Use a delay between updates for readable scrolling speed.
Handle cases where text length is less than or equal to LCD width.
Use substring pointers to shift the visible text window.

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Key Takeaways

Clear the LCD and reset cursor before printing each new substring to avoid display glitches.

Scroll by showing a moving window of the text string that fits the LCD width.

Use a delay between updates to control scroll speed and readability.

Handle short text separately to avoid unnecessary scrolling.

Test on your actual LCD hardware as timing and commands may vary.