MAX7219 7-segment display-Arduino

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MAX7219 Display Driver

The MAX7219/MAX7221 are compact, serial input/output common-cathode display drivers that interface microprocessors 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. A convenient 4-wire serial interface connects to all common micro controllers. Individual digits may be addressed and updated without rewriting the entire display. The MAX7219/MAX7221 also allow the user to select codeB decoding or no-decode for each digit. The devices include a 150µA low-power shutdown mode, analog and digital brightness control, a scan limit register that allows the user to display from 1 to 8 digits, and a test mode that forces all LEDs on.

MAX7219 7-segment Displau Module
MAX7219 7-segment Displau Module

Arduino Connections with Display Module

            MAX7219 display modules comes with 5 pin connector on its end these connections are connected to supply and arduino IO pins. Data, clock and load pins are used similar to the 74595 data, clock and latch pins. Connections are made as shown in figure.

MAX7219 Display Module Connections with Arduino
MAX7219 Display Module Connections with Arduino

Arduino Code for Display Module

We are using “LedControl” Library for this code.

//We always have to include the library
// circuits4you.com
#include "LedControl.h"

/*
 Now we need a LedControl to work with.
 ***** These pin numbers will probably not work with your hardware *****
 pin 7 is connected to the DataIn 
 pin 6 is connected to the CLK 
 pin 5 is connected to LOAD 
 We have only a single MAX72XX.
 */
LedControl lc=LedControl(7,6,5,1);

/* we always wait a bit between updates of the display */
unsigned long delaytime=250;

void setup() {
  /*
   The MAX72XX is in power-saving mode on startup,
   we have to do a wakeup call
   */
  lc.shutdown(0,false);
  /* Set the brightness to a medium values */
  lc.setIntensity(0,8);
  /* and clear the display */
  lc.clearDisplay(0);
}


/*
 This method will display the characters for the
 word "Arduino" one after the other on digit 0. 
 */
void writeArduinoOn7Segment() {
  lc.setChar(0,0,'a',false);
  delay(delaytime);
  lc.setRow(0,0,0x05);
  delay(delaytime);
  lc.setChar(0,0,'d',false);
  delay(delaytime);
  lc.setRow(0,0,0x1c);
  delay(delaytime);
  lc.setRow(0,0,B00010000);
  delay(delaytime);
  lc.setRow(0,0,0x15);
  delay(delaytime);
  lc.setRow(0,0,0x1D);
  delay(delaytime);
  lc.clearDisplay(0);
  delay(delaytime);
} 

/*
  This method will scroll all the hexa-decimal
 numbers and letters on the display. You will need at least
 four 7-Segment digits. otherwise it won't really look that good.
 */
void scrollDigits() {
  for(int i=0;i<13;i++) {
    lc.setDigit(0,3,i,false);
    lc.setDigit(0,2,i+1,false);
    lc.setDigit(0,1,i+2,false);
    lc.setDigit(0,0,i+3,false);
    delay(delaytime);
  }
  lc.clearDisplay(0);
  delay(delaytime);
}

void loop() { 
  writeArduinoOn7Segment();
  scrollDigits();
}

Results

The above code displays arduino on the display and also shows numbers.

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