Overview of MAX7219 7-Segment Display

There are various display modules available in the market that make use of ICs like the MAX7219 to drive multiple 7-segment displays using SPI communication. One such module is shown in the image given below.

These modules are compact and require few pins and wires compared to using singular 7-segment displays in cascade.

MAX7219 7-Segment Display Hardware Connection with ESP32

Display 0 to 7 Digit on 7 Segment display

Here we have used the LedController library.

Download the library from the below link.

https://www.arduino.cc/reference/en/libraries/ledcontroller/

Code for MAX7219 with ESP32

/**
 * @file LCDemo7Segment.ino
 * @author Noa Sakurajin ([email protected])
 * @brief using the ledcontroller with 7-segment displays
 * @version 0.1
 * @date 2020-12-30
 *
 * @copyright Copyright (c) 2020
 *
 */

#include "LedController.hpp"
/*
 You might need to change the following 3 Variables depending on your board.
 pin 15 is connected to the DataIn
 pin 14 is connected to the CLK
 pin 13 is connected to LOAD/ChipSelect
*/
#define DIN 15
#define CS 13
#define CLK 14

/*
 Now we need a LedController Variable to work with.
 We have only a single MAX72XX so the Dimensions are 1,1.
 */
LedController<1,1> lc;

/* we always wait a bit between updates of the display */
unsigned long delaytime=1000;

void setup() {
  //Here a new LedController object is created without hardware SPI.
  lc=LedController<1,1>(DIN,CLK,CS);
  lc.setIntensity(8); /* Set the brightness to a medium values */
  lc.clearMatrix(); /* and clear the display */
}

void loop() {
  for(int i=0; i<8; i++) {
    lc.setDigit(0,i,i,false);
    delay(delaytime);
  }
  lc.clearMatrix();
  delay(delaytime);
}

• Now upload the code. (While uploading the code make sure your ESP32 board is in the boot mode.)

Output

Let’s Understand the code

Set the SPI pin number 

#define DIN 15
#define CS 13
#define CLK 14

Now we need a LedController Variable to work with.

We have only a single MAX72XX so the Dimensions are 1,1.

LedController<1,1> lc;

we always wait a bit between updates of the display

unsigned long delaytime=1000;

In setup function

Here we have created a new LedController object.

lc=LedController<1,1>(DIN,CLK,CS);

Set the display brightness to medium values

lc.setIntensity(8);

Clear the display

lc.clearMatrix();

In loop function

Set the digit and show it on the 7-segment display 

for(int i=0; i<8; i++) {
  lc.setDigit(0,i,i,false);
  delay(delaytime);
}

Here wait for the delay time

delay(delaytime);