22. MAX7219/MAX7221: Control two independent 7-segment display

	Arduino Nano
	Breadboard
	7 segment display Type: 5161AB, Blue, Common Cathode, 0.56 inch
	Capacitor, 10 µF 25V
	MAX7221 pdf
	Wire
	Resistor 10K ohm

	Capacitor 5v rail <=> gnd rail Arduino Nano 5v <=> 5v rail gnd <=> gnd rail
	Arduino Nano <=> MAX7221 (blue) D12 <=> DIN (1) D11 <=> CLK (13 D10 <=> LOAD (12)
	Daisy chain first 7 segment display to second 7 segment display
	MAX7221 <=> Rail ISET (18) 10k resistor <=> 5V rail (Controls brightness) GND (4) <=> GND rail GRD (9) <=> GND rail 5V (19) <=> 5V rail
	MAX7221 <=> 7 segment display DIG0 (2) <=> Common cathode first 7 segment display DIG1 (11) <=> Common cathode second 7 segment display SEGA (14) <=> A SEGB (16) <=> B SEGC (20) <=> C SEGD (23) <=> D SEGE (21) <=> E SEGF (15) <=> F SEGG (17) <=> G

Code:

#include <LedControl.h>

LedControl lc = LedControl(12, 11, 10, 1);  // datapin, clockpin, cs   1 = number of MAX7221 devices
unsigned long delaytime = 250;

void setup() {
  lc.shutdown(0, false);  // Wake up device 0
  lc.setIntensity(0, 8);  // Brightness (0–15) for device 0
  lc.clearDisplay(0);     // Clear display 0
}

void loop() {
  for (int num = 0; num < 100; num++) {
    int tens = num / 10;  // Extract tens digit
    int ones = num % 10;  // Extract ones digit

    lc.setDigit(0, 0, tens, false);  // device 0 display 0
    lc.setDigit(0, 1, ones, false);  // device 0 display 1

    delay(1000);
  }
}

Ino file
Source and examples LedControl