MAX7219 not updating 7 seg display

Projects Programming
1

Howdy,
This has me puzzled. I have a MAX7219 connected to a 5 digit 7 segment display.
I can set the digits to whatever I want in setup(), but I tried making a simple counter, and it will not update.
I say it will not update, but sometimes it will a couple of times and then just go blank.

#include <LedControl.h>
#include <time.h>
LedControl mydisplay = LedControl(52, 54, 56, 1); 
int delayTime = 500;
byte digit= 0;  // I have tried int as well
unsigned int currentTime  = 0;
unsigned int lastChange  = 0;

void setup() {
  // this works 
  mydisplay.shutdown(0, false);
  mydisplay.setIntensity(0, 8); 
  mydisplay.setDigit(0, 0, 8, true);
  mydisplay.setDigit(0, 1, 8, true);
  mydisplay.setDigit(0, 2, 8, true);
  mydisplay.setDigit(0, 3, 8, true);
  mydisplay.setDigit(0, 4, 8, true);
  // every part of the display is lit

  delay(1000);               

  mydisplay.clearDisplay(0);
  delay(500);               
  lastChange = millis();    
  currentTime = millis();
  lastChange = currentTime;    
}
void loop() {
  currentTime = millis();
  if ((lastChange + delayTime) <= currentTime)
  {
    lastChange = currentTime;
    digit = digit + 1;
    if (digit == 10)
       digit = 1;
    // this might work or might not...generally not... ????
    // if it does, it won't get through the count all the way
    mydisplay.setDigit(0, 0, digit, true);
  }

I appreciate any feedback.
Thanks,
John

2

Since millis() returns a long, currentTime and lastChange should be declared as unsigned long.

NB.: I didn't look for possible other errors.