Why doesn't my 7 segment update every second like in the program?

Question

I used sevseg.h library to write numbers to my 4 digit seven segment. The display should update every second with the current time since program started running. This is my code so far:

#include <SevSeg.h>

SevSeg sevseg;

void setup() {
    byte numDigits = 4;
    byte digitPins[] = {5, 4, 3, 2};
    byte segmentPins[] = {13, 12, 11, 10, 9, 8, 7, 6};
    sevseg.begin(COMMON_CATHODE, numDigits, digitPins, segmentPins);
    sevseg.setBrightness(50);
    sevseg.setNumber(0000, -1);
}

void loop() {
    unsigned long timer = millis();
    for (int i = 0; i < 500; i++) {
        sevseg.setNumber(timer/1000, -1);
        sevseg.refreshDisplay();
        delay(2);
    }
}

Since the delay is 2, the for loop loops 500 times, resulting in 1000ms or 1 second. The current second is written to the display. For some reason, the display is updated every other 5 or 6 seconds. Why is this occurring? How can this be fixed so that my display turns into a stopwatch in a way?

Answer 1

This is the code that fixed the issue:

  #include <SevSeg.h>
  SevSeg sevseg;

  void setup() {
    byte numDigits = 4;
    byte digitPins[] = {5, 4, 3, 2};
    byte segmentPins[] = {13, 12, 11, 10, 9, 8, 7, 6};
    sevseg.begin(COMMON_CATHODE, numDigits, digitPins, segmentPins);
    sevseg.setBrightness(50);
    sevseg.setNumber(0000, -1);
  }

  void loop() {
    unsigned long timerGlobal = millis();
    sevseg.setNumber(timerGlobal/1000, -1);
    sevseg.refreshDisplay();
  }

In this, no delays are needed. millis is divided by 1000 and the integer second is drawn on the display. Proved to be much easier than I previously thought.

Answer 2

On SevSeg.h Arduino Page, It says:

Your program must run the refreshDisplay() function repeatedly to display the number.

I think that's the Problem. You are calling it just once and then your the number is changed.

Plus, you are saying it must get updated after One Second, but I think in your code, its being updated ever other 2 milisecond (WOW).

What I suggest is that you add a delay() for one second and then call sevseg.refreshDisplay(); several times in a for loop. You also need to change the way you measure no. of seconds elapsed.

i.e. try Something like this:

#include <SevSeg.h>
SevSeg sevseg;
void setup() {
  byte numDigits = 4;
  byte digitPins[] = {5, 4, 3, 2};
  byte segmentPins[] = {13, 12, 11, 10, 9, 8, 7, 6};
  sevseg.begin(COMMON_CATHODE, numDigits, digitPins, segmentPins);
  sevseg.setBrightness(50);
  sevseg.setNumber(0000, -1);
}
unsigned long timerGlobal = millis();
void loop() {
  delay(1000);
  sevseg.setNumber( (timerGlobal - millis())/1000, -1)
  for (int i = 0; i < 50; i++) {
    sevseg.refreshDisplay();
  }
}