Demo 5: How to use Arduino ESP32 to display information on SPI LED matrix - IoT Sharing

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Monday, May 15, 2017

Demo 5: How to use Arduino ESP32 to display information on SPI LED matrix

1. Introduction
This demonstration show you how to connect a LED Matrix module to Arduino ESP32 via MAX7219 module to display information from ESP32. There are 2 ways to connect ESP32 to LED Matrix module:
  • Connect directly. By using this way, ESP32 will waste many GPIO pins (at lest 8x8 for 8x8 Led matrix).
  • Connect via MAX7219 module. By using this way, ESP32 will only use 3 GPIO pins which act as SPI MOSI, CLK and CS pins. MAX7219 will be responsible for converting SPI data to LED Matrix data and control signals.

 
Figure: Led matrix
2. Hardware
Connect the pins of ESP32 to the pins of LED matrix:
[ESP32 GPIO14 - LED CLK] 
[ESP32 GPIO12 - LED DIN (MOSI)]
[ESP32 GPIO15 - LED CS]
[ESP32 GND - LED GND]
[LED VCC - 5V]
or follow picture below:
Figure: ESP32 connect to LED matrix module
3. Software
We will use the library MAX7219LedMatrix that is made for Arduino but I modified a little to compatible with ESP32. You can download the library here:


After downloading, unzip and copy the unzipped folder under folder:


The library supplied some functions:

  • init(): to initialize library
  • setText(): set the text to print on LED Matrix
  • scrollTextLeft(): scroll text to left effect
  • clear(): clear the display
  • drawText(): start drawing text to buffer
  • commit(): commit the text from buffer to LED Matrix

In order to use these function you need to create an instance of LedMatrix with constructor: LedMatrix ledMatrix=LedMatrix(NUMBER_OF_DEVICES, CLK_PIN, MISO_PIN, MOSI_PIN, CS_PIN)

Note: NUMBER_OF_DEVICES number of cascading LED Matrix in a serial mode


Figure: 4 LED Matrix in a serial mode
Finally, you create an Arduino project and save it as esp32ledmatrix with code:
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#include <SPI.h>
#include "LedMatrix.h"
#define NUMBER_OF_DEVICES 3 //number of led matrix connect in series
#define CS_PIN 15
#define CLK_PIN 14
#define MISO_PIN 2 //we do not use this pin just fill to match constructor
#define MOSI_PIN 12

LedMatrix ledMatrix = LedMatrix(NUMBER_OF_DEVICES, CLK_PIN, MISO_PIN, MOSI_PIN, CS_PIN);
  
void setup() {
  ledMatrix.init();
  ledMatrix.setText("EasyIoT");
}

void loop() {
  ledMatrix.clear();
  ledMatrix.scrollTextLeft();
  ledMatrix.drawText();
  ledMatrix.commit();
  delay(50);
}

4. Result



Figure: ESP32 connect to LED matrix

2 comments:

Anonymous said...

Hello

Nice job.
I've purchase a 4in1 display module and i've try your program.

The problem is the scroling direction.
Your program scrol the text left to right (or right to the left).
But the module are conected from the bottom to the top.
So i need o modify your program in order to scrol the text from the top of the lower display to the bottom of the next display.
(ie: i need to shift the data not on the column but on the row)
I don't kown if it's possible.

Talaj Munka said...

https://www.aliexpress.com/item/MAX7219-dot-matrix-module-microcontroller-module-4-in-one-display/32668446642.html?spm=a2g0s.9042311.0.0.27424c4dJiPFQq
Cserélje ki a < LedMatrix.cpp > -ben a 102.sorban "void LedMatrix::commit()" részt az alábbiakra:

void LedMatrix::commit() { //shift the data not on the column but on the row
byte Jav_cols[32];
for (byte digit = 0; digit < 4; digit++){
for (byte sor = 0; sor < 8; sor++){
for (byte oszlop = 0; oszlop < 8; oszlop++){
bitWrite(Jav_cols[7-sor +(digit*8)], oszlop, bitRead(cols[oszlop+(digit*8)], sor)); }}}
for (byte digit = 0; digit < 4; digit++){
for (byte oszlop = 0; oszlop < 8; oszlop++){
sendByte(digit, oszlop, (Jav_cols[oszlop+24-digit*8]));
}}}

Thường mất vài phút để quảng cáo xuất hiện trên trang nhưng thỉnh thoảng, việc này có thể mất đến 1 giờ. Hãy xem hướng dẫn triển khai mã của chúng tôi để biết thêm chi tiết. Ðã xong