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INTERNET OF THING (IoT)

ESP32 - LED Matrix

LED matrix display, also known as LED display, or dot matrix display, are wide-used. In this tutorial, we are going to learn:

LED matrix
How to connect ESP32 to 8x8 LED matrix
How to connect ESP32 to 32x8 LED matrix
How to connect ESP32 to display text, numbers, and animated effects on the LED matrix.

After that, you can easily adapt the code for other LED matrices such as 16x8 LED matrix, 64x8 LEd matrix ...

Hardware Used In This Tutorial

1	×	ESP-WROOM-32 Dev Module
1	×	USB Cable Type-C
1	×	FC-16 LED Matrix 32x8
1	×	FC-16 LED Matrix 8x8
1	×	Generic LED Matrix 8x8
1	×	Breadboard
1	×	Jumper Wires
1	×	(Optional) DC Power Jack
1	×	(Recommended) ESP32 Screw Terminal Adapter

Or you can buy the following sensor kit:

1

×

DIYables Sensor Kit 30 types, 69 units

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Introduction to LED Matrix

LED Matrix display

There are many kinds of LED Matrix. With ESP32, the MAX7219-based LED matrix is widely used. MAX7219-based LED matrix has the following features:

A base unit of an LED matrix is a block
Each block has an 8x8 LED matrix (64 LED) and a MAX7219 driver.
There are two popular block forms: the generic module and the FC-16 module.
A LED matrix can be composed of a single block or multiple blocks in a daisy-chain
You can buy a pre-built multiple-block LED Matrix (e.g. 4-in-1, 8-in-1)
You can also buy multiple blocks and wire them to form a LED matrix with the desired size.
You will declare the size of the LED matrix you use in the ESP32 code.

Pinout

LED Matrix Pinout

A LED Matrix is formed by a single or multiple blocks. Each block includes two groups of pins:

Input pins group:

VCC: connects to 5V.
GND: connects to GND.
DIN is the Data pin, Connect it to any digital pin of the ESP32.
CS: Chip Select, Connect it to any digital pin of the ESP32.
CLK: Clock pin, Connect it to any digital pin of the ESP32.

Output pins group:

VCC: connects to VCC of the input pins group on the next module.
GND: connects to GND of the input pins group on the next module.
DOUT: Data Out, connects to the DIN pin of the input pins group of the next module.
CS: connects to CS of the input pins group on the next module.
CLK connects to CLK of the input pins group on the next module.

Wiring Diagram

If the LED matrix is made of a single block:

Connect the input pins groups to ESP32
Let the output pins group unconnected

ESP32 8x8 LED matrix FC-16 wiring diagram

This image is created using Fritzing. Click to enlarge image

If you're unfamiliar with how to supply power to the ESP32 and other components, you can find guidance in the following tutorial: How to Power ESP32.

ESP32 8x8 LED matrix generic wiring diagram

This image is created using Fritzing. Click to enlarge image

If the LED matrix is pre-built multiple blocks:

Connect the input pins groups to ESP32
Let the output pins group unconnected

ESP32 LED matrix display wiring diagram

This image is created using Fritzing. Click to enlarge image

If the LED matrix is made of multiple blocks by yourself:

Connect the input pins groups of the first block to ESP32
Connect the output pins groups of each block to the input pins groups of the next block
Let the output pins group of the last block unconnected

ESP32 32x8 LED matrix wiring FC-16 diagram

This image is created using Fritzing. Click to enlarge image

ESP32 32x8 LED matrix wiring generic diagram

This image is created using Fritzing. Click to enlarge image

Because the display draws a lot of currents (up to 1A at maximum brightness):

Do not use the power from the 5V pin of ESP32.
Use an external 5V power supply instead. ESP32 and LED matrix can share power from a 5V power adapter

Because ESP32 connects to LED matrix via SPI pins:

Pin GPIO18 (SCK) and GPIO23 (MOSI) on ESP32
Pin GPIO21 (CS) can be changed to any pin

How To Program For LED Matrix

It is not easy to control the LED matrix. Fortunately, libraries are available to make it easy. Below is a step-by-step on how to write ESP32 code to control the LED matrix

Include libraries:

#include <MD_Parola.h> #include <MD_MAX72xx.h>

Specify which hardware is being used: GENERIC_HW or FC16_HW.

#define HARDWARE_TYPE MD_MAX72XX::FC16_HW

Define how many LED block is used. for example, a 4-in-1 LED matrix has 4 blocks.

#define MAX_DEVICES 4

Define the pin that connects to the LED matrix’s CS pin. For example, pin GPIO21

#define CS_PIN 21

Create a new instance of the MD_Parola class for the LED matrix display.

MD_Parola ledMatrix = MD_Parola(HARDWARE_TYPE, CS_PIN, MAX_DEVICES);

Code in the setup() function:

void setup() { ledMatrix.begin(); // initialize the object ledMatrix.setIntensity(0); // set the brightness of the LED matrix display (from 0 to 15) ledMatrix.displayClear(); // clear led matrix display }

Display text, number and show animated effects: see next part

ESP32 - LED Matrix Code

The below code is for 32x8 FC-16 LED matrix display (4 blocks). But you can easily adapt it for 8x8, 16x8, 64x8...

/* * This ESP32 code is created by esp32io.com * * This ESP32 code is released in the public domain * * For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-led-matrix */ #include <MD_Parola.h> #include <MD_MAX72xx.h> #define HARDWARE_TYPE MD_MAX72XX::FC16_HW #define MAX_DEVICES 4 // 4 blocks #define CS_PIN 21 // create an instance of the MD_Parola class MD_Parola ledMatrix = MD_Parola(HARDWARE_TYPE, CS_PIN, MAX_DEVICES); void setup() { ledMatrix.begin(); // initialize the LED Matrix ledMatrix.setIntensity(0); // set the brightness of the LED matrix display (from 0 to 15) ledMatrix.displayClear(); // clear LED matrix display } void loop() { ledMatrix.setTextAlignment(PA_LEFT); ledMatrix.print("Left"); // display text delay(2000); ledMatrix.setTextAlignment(PA_CENTER); ledMatrix.print("Center"); // display text delay(2000); ledMatrix.setTextAlignment(PA_RIGHT); ledMatrix.print("Right"); // display text delay(2000); ledMatrix.setTextAlignment(PA_CENTER); ledMatrix.setInvert(true); ledMatrix.print("Invert"); // display text inverted delay(2000); ledMatrix.setInvert(false); ledMatrix.print(1234); // display number delay(2000); }

Quick Instructions

If this is the first time you use ESP32, see how to setup environment for ESP32 on Arduino IDE.
Do the wiring as above image.
Connect the ESP32 board to your PC via a micro USB cable
Open Arduino IDE on your PC.
Select the right ESP32 board (e.g. ESP32 Dev Module) and COM port.
Click to the Libraries icon on the left bar of the Arduino IDE.
Search “MD_Parola”, then find the MD_Parola library
Click Install button.

ESP32 MD_Parola library

You will be asked to install the “MD_MAX72XX” library
Click Install All button to install the dependency.

ESP32 MD_MAX72XX library

Copy the above code and open it with Arduino IDE
Click Upload button on Arduino IDE to upload code to ESP32
See the LED matrix display

ESP32 LED Matrix Code – Scrolling Text

When you want to print a long message that is too long to fit on a LED matrix display, you can use the scroll text effect technique.

The below ESP32 code shows how to scroll a message on the LED matrix display.

/* * This ESP32 code is created by esp32io.com * * This ESP32 code is released in the public domain * * For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-led-matrix */ #include <MD_Parola.h> #include <MD_MAX72xx.h> #define HARDWARE_TYPE MD_MAX72XX::FC16_HW #define MAX_DEVICES 4 // 4 blocks #define CS_PIN 21 // create an instance of the MD_Parola class MD_Parola ledMatrix = MD_Parola(HARDWARE_TYPE, CS_PIN, MAX_DEVICES); void setup() { ledMatrix.begin(); // initialize the object ledMatrix.setIntensity(0); // set the brightness of the LED matrix display (from 0 to 15) ledMatrix.displayClear(); // clear led matrix display ledMatrix.displayScroll("ESP32", PA_CENTER, PA_SCROLL_LEFT, 100); } void loop() { if (ledMatrix.displayAnimate()) { ledMatrix.displayReset(); } }

For more text effects, please visit MD_Parola Library Reference.

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