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8x8 led matrix interfacing with arduino

About the project

I use 788bs, a common anode 8x8 led matrix Modules for this project. Learn how to identify matrix pinout, how to interface with Arduino.

Project info

Difficulty: Moderate

Platforms: Digilent

Estimated time: 1 hour

License: GNU Lesser General Public License version 3 or later (LGPL3+)

Items used in this project

Hardware components

	Jumper wires (generic)	x 1
	AA Batteries	x 1
	Solderless Breadboard Full Size	x 1
	LED Dot Matrix Display, Green	x 1
	Arduino UNO	x 1

Software apps and online services

	Multitool, Screwdriver
	Digilent Mastech MS8217 Autorange Digital Multimeter
	Arduino IDE

Story

There are several types of led matrix displays available in the market. It also comes with Arduino kits. We can understand it in size and types, e.g. 5x7, 8x8, common anode, and common cathode type.

1 / 2 • Led matrix

Led matrix

Led matrix

But in this article, I will discuss 788bs as a common anode 8x8 red color matrix Modules. We use it in many electronics displaying items, e.g. electronics clocks. also for moving message displays, displaying games, etc.

We use a dot matrix display with an Arduino UNO board directly, sometimes in projects. But for some projects, we use a max7219 chip or 74hc595 for dot matrix driver as required in our projects.

Led matrix Pinout

Led matrix Pinout

8x8 led Matrix Pinout details

The dot-matrix modules most of the time comes in red led. It is easy to attach with an Arduino board as compared to an RGB led display.

If we look at a piece of the 8x8 dot matrix, it contains 16 pins in which 8 pins used for rows and 8 for columns. That's mean in rows and column a total of 64 LEDs.We start from Pin # 1 to pin # 8. Pin number 1 is R5 (Row-5) and Pin number 8 is R3(Row-3) at the downside.

At the upper side From Pin 9 (Row-1) to Pin 16 (column-1) located. But a newbie always confuses and starts from zero, because we know the picture/diagram. often we get from some source, also we have to sort out which one +VE and -VE. might be an expert can understand from common cathode/anode type.

But my concern about the person has a basic knowledge of electronics. Who try to make their own initial display projects like a clock or some more.

Ok let’s start if we have an 8x8 dot matrix, And how do we know where pin 1 is? As in IC Chips near Pin 1, a dot mentioned at IC/Microcontroller Chip. But here, how do we know?

Pins Starts at knob side

Pins Starts at knob side

At the led matrix module, the manufacturer writes the tag or mark at pin 1 side, as shown in the figure. We definitely find it. And also a curve mentioned at pin number 1 side.

Battery connection

Battery connection

Row = + Positive Supply

Column = - Negative Supply

The testing power supply should be 1.5V DC required. So the only one battery cell enough or uses one 130 ohm resistance in series at a positive/negative side.

Led matrix Testing with Battery cell

Led matrix Testing with Battery cell

After that attached led to the power supply. We found that the 8th column and 5th rows led become ON as Connection shown in the figure. How to connect the battery cell with a matrix display.

Column and Row Pin connection

Column and Row Pin connection

Pin Test of led dot matrix

As shown in fig pin # 1 and pin # 16 got Energize and 8th Column and 5th-row led become ON. We should verify the Dot-matrix before using it because if any led found blown we can replace it with a good one.

Led matrix light up

Led matrix light up

Programming with Arduino UNO

To run the 788bs, you need to check it with Arduino UNO. What material you need to perform a complete test.

Arduino UNO Amazon

Breadboard Amazon / Banggood

788BS 8x8 matrix Amazon / Banggood

Battery (1.5V) only one

Jumper wires

We often use the dot matrix display with the shift register 74HC595 led driver or max7219. most common in electronic Circuits, we operate it with a Microcontroller or Arduino platform, and even with Raspberry Pi. But in this circuit, you can test the matrix direct with an Arduino UNO board.

Interface dot matrix with Arduino

First setting up the matrix circuit, as per the connection given in the picture diagram. start the Arduino IDE to program the Arduino UNO board. Arduino IDE is available at Arduino official site. For this circuit, it does not need resistance at all. Just connect wires as per the instruction.

Here you need two steps before starting a matrix connection with Arduino as per the 788bs datasheet matrix pins connection given.

1- 8x8 led matrix code generator

This will help to generate code for your matrix. Just draw anything for the matrix, copy the code, and use it in your program. You can draw different symbols, shapes, or words.

2- Add matrix library with Arduino Ide

First, add the 8x8 led dot matrix library in Arduino Ide. hereafter, the library manager in Arduino Ide will run the code. It will display in the matrix.

The connection between Led matrix and Arduino UNO

Matrix Rows Pins # ------------ Arduino Uno output Pins

Pin # 1 ---------- 2

2 ---------- 3

3 ---------- 4

4 ---------- 5

5 ---------- 6

6 ---------- 7

7 ---------- 8

8 ---------- 9

Matrix Column: Pins # ----------------- Arduino Uno output Pins #

Pin # 1 ------------ 10

2 ------------ 11

3 ------------ 12

4 ------------ 13

5 ------------ A1

6 ------------ A2

7 ------------ A3

8 ------------ A4

Schematics, diagrams and documents

Pin connection led matrix

8x8 led matrix connection diagram

Code

Led matrix display running

To display as you like, I display a moving a Person.

// Pins connect as per define
// Fill in the pins you used on your own setup.

#define ROW_1 2
#define ROW_2 3
#define ROW_3 4
#define ROW_4 5
#define ROW_5 6
#define ROW_6 7
#define ROW_7 8
#define ROW_8 9

#define COL_1 10
#define COL_2 11
#define COL_3 12
#define COL_4 13
#define COL_5 A0
#define COL_6 A1
#define COL_7 A2
#define COL_8 A3

const byte rows[] = {
    ROW_1, ROW_2, ROW_3, ROW_4, ROW_5, ROW_6, ROW_7, ROW_8
};

// The display buffer
// It shows a walking steps (1 = ON, 0 = OFF)
byte star1[] = {B00000110,B11000010,B10100100,B00011000,B00011000,B00100101,B01000011,B01100000};
byte star2[] = {B00110000,B00100000,B00100111,B00011001,B10011000,B11100100,B00000100,B00001100};
byte star3[] = {B00000110,B10001000,B10010000,B01011100,B00111010,B00001001,B00010001,B01100000};

float timeCount = 0;

void setup() {
    // Open serial port
    Serial.begin(9600);
    
    // Set all used pins to OUTPUT
    // This is very important! If the pins are set to input
    for (byte i = 2; i <= 13; i++)
        pinMode(i, OUTPUT);
    pinMode(A0, OUTPUT);
    pinMode(A1, OUTPUT);
    pinMode(A2, OUTPUT);
    pinMode(A3, OUTPUT);
}

void loop() {
  // This could be rewritten to not use a delay, which would make it appear brighter
delay(5);
timeCount += 1;
if(timeCount <  20) {
drawScreen(star1);
} else if (timeCount <  80) {
drawScreen(star2);
} else if (timeCount <  100) {
drawScreen(star3);
} else if (timeCount <  120) {
drawScreen(star1);
} else if (timeCount <  140) {
drawScreen(star2);
} else if (timeCount <  160) {
drawScreen(star3);
} else {
// back to the start
timeCount = 0;
}
}
 void  drawScreen(byte buffer2[]){
     
    
   // Turn on each row in series
    for (byte i = 0; i < 8; i++) {
        setColumns(buffer2[i]); // Set columns for this specific row
        
        digitalWrite(rows[i], HIGH);
        delay(2); // Set this to 50 or 100 if you want to see the multiplexing effect!
        digitalWrite(rows[i], LOW);
        
    }
}


void setColumns(byte b) {
    digitalWrite(COL_1, (~b >> 0) & 0x01); // Get the 1st bit: 10000000
    digitalWrite(COL_2, (~b >> 1) & 0x01); // Get the 2nd bit: 01000000
    digitalWrite(COL_3, (~b >> 2) & 0x01); // Get the 3rd bit: 00100000
    digitalWrite(COL_4, (~b >> 3) & 0x01); // Get the 4th bit: 00010000
    digitalWrite(COL_5, (~b >> 4) & 0x01); // Get the 5th bit: 00001000
    digitalWrite(COL_6, (~b >> 5) & 0x01); // Get the 6th bit: 00000100
    digitalWrite(COL_7, (~b >> 6) & 0x01); // Get the 7th bit: 00000010
    digitalWrite(COL_8, (~b >> 7) & 0x01); // Get the 8th bit: 00000001
    
    // If the polarity of your matrix is the opposite of mine
    // remove all the '~' above.
}

Credits

shahbaz75sb

electronics Eng

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