IoT Practicals / LED Matrix Display

8x8 LED Matrix Display - Pattern Control

Objective: Control an 8x8 LED matrix to display custom patterns using the LedControl library.

This project demonstrates advanced display control, binary pattern creation, and multiplexed LED driving techniques for visual IoT applications.

Required Components:

Letter 'D' Pattern:

01111100
01000010
01000010
01000010
01000010
01000010
01111100
00000000

Binary representation of the letter 'D' displayed on the matrix

#include < LedControl.h>

#define NBR_MTX 1
LedControl lc = LedControl(12, 11, 10, NBR_MTX);

void setup() {
  for (int i = 0; i < NBR_MTX; i++) {
    lc.shutdown(i, false);
    lc.setIntensity(i, 8);
    lc.clearDisplay(i);
    delay(500);
  }
}

void loop() {
  byte D_pattern[8] = {
    0b01111100,
    0b01000010,
    0b01000010,
    0b01000010,
    0b01000010,
    0b01000010,
    0b01111100,
    0b00000000
  };

  for (int row = 0; row < 8; row++) {
    for (int col = 0; col < 8; col++) {
      lc.setLed(0, row, col, bitRead(D_pattern[row], 7 - col));
    }
  }

  delay(1000);
  lc.clearDisplay(0);
  delay(1000);
}

How it works:

  • LedControl Library: Manages MAX7219 LED driver chip for matrix control.
  • Pin Configuration: DIN→12, CLK→11, CS→10 for SPI communication.
  • shutdown(false): Activates the display (removes power-saving mode).
  • setIntensity(8): Sets brightness level (0-15, where 8 is medium).
  • Binary Patterns: Each byte represents one row of 8 LEDs.
  • bitRead(): Extracts individual bits to control each LED.
  • Animation Loop: Display pattern for 1 second, clear for 1 second, repeat.

Circuit Connection:

  • VCC → 5V (Arduino or external power)
  • GND → Ground
  • DIN → Arduino Pin 12 (Data In)
  • CS → Arduino Pin 10 (Chip Select)
  • CLK → Arduino Pin 11 (Clock)

Pattern Creation Tips:

  • Each byte (0b01111100) represents one row of 8 LEDs
  • 1 = LED ON, 0 = LED OFF
  • Create custom patterns by modifying the binary values
  • Use online LED matrix pattern generators for complex designs

Applications:

  • Digital clocks and timers
  • Text scrolling displays
  • Game status indicators
  • Weather station displays
  • Interactive art installations