MAX 7219 Countdown Timer

Other Hardware LEDs and Multiplexing
1

Hi, First post please excuse me if this is wrong in any way. First Arduino project ever! yay i want to make a 9x7 display countdown for 45mins on an input and then set off a buzzer (or other output) i've found some previous code in this forum and tried to adapt it but the issue is time displaying as time and then counting down correctly. Please help

#include "LedControl.h"


/*pin 12 is connected to the DataIn 
pin 11 is connected to the CLK 
pin 10 is connected to LOAD 
We have only a single MAX72XX.
*/
LedControl lc=LedControl(12,11,10,1);

unsigned long delaytime=1;

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);
}

int time = 0;
int s0 = 0;
int s1 = 0;
int s2 = 0;
int s3 = 0;
int s4 = 5;
int s5 = 4;
int s6 = -1;
int s7 = -1;
void loop() { 
  
  s0=time;
  
  if (time==9){
    time=-1;
  }
  
  if (s0==0){
    s1=s1+1;
  }
  
  //---------------------------------------------------------
  
    if (s1==10){
    s1=0;
  }
  
  if (s1==0&&s0==0){
    s2=s2+1;
  }
  
  //---------------------------------------------------------
  
     if (s2==10){
    s2=0;
  }
  
  if (s2==0&&s1==0&&s0==0){
    s3=s3+1;
  }
  
    //---------------------------------------------------------
  
     if (s3==10){
    s3=0;
  }
  
  if (s3==0&&s2==0&&s1==0&&s0==0){
    s4=s4+1;
  }
  
      //---------------------------------------------------------
  
     if (s4==10){
    s4=0;
  }
  
  if (s4==0&&s3==0&&s2==0&&s1==0&&s0==0){
    s5=s5+1;
  }
  
        //---------------------------------------------------------
  
     if (s5==10){
    s5=0;
  }
  
  if (s5==0&&s4==0&&s3==0&&s2==0&&s1==0&&s0==0){
    s6=s6+1;
  }
  
          //---------------------------------------------------------
  
     if (s6==10){
    s6=0;
  }
  
  if (s6==0&&s5==0&&s4==0&&s3==0&&s2==0&&s1==0&&s0==0){
    s7=s7+1;
  }
  
  
  lc.setChar(0,0,s0 ,false);
  lc.setChar(0,1,s1 ,false);
  lc.setChar(0,2,s2 ,false);
  lc.setChar(0,3,s3 ,false);
  lc.setChar(0,4,s4 ,false);
  lc.setChar(0,5,s5 ,false);
  lc.setChar(0,6,s6 ,false);
  lc.setChar(0,7,s7 ,false);
  
   delay(delaytime);
  time=time+1;
}
2

Hi.

A single max7219 chip can only run up to 8 digits of 7 seg display. Why do you think you need 9 digits for a 45 min countdown?

Please explain what you meant by "the issue is time displaying as time and then counting down correctly". Describe what happens, how that is wrong, and what you want to happen.

The code you posted will also be inaccurate and lose many seconds over 45 mins.