Max7219 8×8 LED matrix example

The MAX7219/MAX7221 are compact, serial input/output common-cathode display drivers that interface microprocessors (µPs) to 7-segment numeric LED displays of up to 8 digits, bar-graph displays, or 64 individual LEDs.

Included on-chip are a BCD code-B decoder, multiplex scan circuitry, segment and digit drivers, and an 8×8 static RAM that stores each digit.

Only one external resistor is required to set the segment current for all LEDs. The MAX7221 is compatible with SPI™, QSPI™, and MICROWIRE™, and has slew-rate-limited segment drivers to reduce EMI.

Features
● 10MHz Serial Interface
● Individual LED Segment Control
● Decode/No-Decode Digit Selection
● 150μA Low-Power Shutdown (Data Retained)
● Digital and Analog Brightness Control
● Display Blanked on Power-Up
● Drive Common-Cathode LED Display

Here is a picture of a typical module that can be bought from many sources, including the link at the end of the article

Parts List

Here are the parts I used

 

Name Links
Wemos Mini
MAX7219
Connecting cables

 

Schematics

wemos and max7219 _bb

Code

You will need the library from https://github.com/squix78/MAX7219LedMatrix

 

#include <SPI.h>
#include "LedMatrix.h"

#define NUMBER_OF_DEVICES 1
#define CS_PIN D4
LedMatrix ledMatrix = LedMatrix(NUMBER_OF_DEVICES, CS_PIN);

void setup() 
{
  ledMatrix.init();
  ledMatrix.setIntensity(4); // range is 0-15
  ledMatrix.setText("The quick brown fox jumps over the lazy dog");
}

void loop() 
{
  ledMatrix.clear();
  ledMatrix.scrollTextLeft();
  ledMatrix.drawText();
  ledMatrix.commit();
  delay(200);
}

 

Link

https://www.analog.com/media/en/technical-documentation/data-sheets/MAX7219-MAX7221.pdf

2 COMMENTS

  1. Hello guy’s,
    at first I have to say that I am a beginner. I read these instruction but I am confused.
    Schematics show connection to 3.3 V. Specification of LED Matrix from MAX7219 say’s it works with

    Operating Voltage: DC 4.7V – 5.3V
    Typical Voltage: 5V
    Operating Current: 320mA
    Max Operating Current: 2A

    my questions:
    – why using 3.3V (and not 5V)
    – If I use power from Wemos D1 can these kill my board because
    board can’t support so muh mA for MAX7219 ?
    Thx

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