Button counter/stopwatch?

[DaveX]

Up on the top right, the days & all add up to 140% of a millis rollover:

(70*86400+0*3600+3*60+52)*1000/2^32 = 1.408214

I don't see any hint of an RTC, so it might have the 0.5% accuracy of the Uno's ceramic oscillator.

I think I'd "handle rollover" by counting seconds into a uint32_t. And use a controller with crystal accuracy.

I'd start with multiple LCDs as in

Multiple_LCDs - Wokwi ESP32, STM32, Arduino Simulator

Add a button and use:

@DaveX

• Planning and Implementing an Arduino Program by @Robin2-- A great way to plan your program to be flexible, easy to read, understand, maintain, and extend.
• Demonstration code for several things at the same time by @Robin2-- An example running a couple blinking LEDS, a button and two servos, all independently. (Live Simulation)

A bit like this:

CountTimerMultLCD - Wokwi ESP32, STM32, Arduino Simulator

code

// https://wokwi.com/projects/405684473173069825
// for https://forum.arduino.cc/t/button-counter-stopwatch/1289236/6
// based on 
// https://wokwi.com/projects/359393073615174657

#include <Wire.h>
#include <hd44780.h>                       // https://github.com/duinoWitchery/hd44780
#include <hd44780ioClass/hd44780_I2Cexp.h> // i2c expander i/o class header

//hd44780_I2Cexp lcd(0x27); // declare lcd object: auto locate & auto config expander chip
// or autoconfigure:
hd44780_I2Cexp lcd(0x27); // declare lcd object: auto locate & auto config expander chip

// Configure 2nd LDC in Wokwi with i2c-address per https://docs.wokwi.com/parts/wokwi-lcd1602
hd44780_I2Cexp lcdB; // declare lcd object: auto locate & auto config expander chip
hd44780_I2Cexp lcdC; // declare lcd object: auto locate & auto config expander chip
hd44780_I2Cexp lcdD; // declare lcd object: auto locate & auto config expander chip


const byte ButtonPin = A0;
uint32_t seconds = 0; // remember seconds since boot
uint32_t lastChangeMs, lastPressMs = 0; // button timings
uint32_t maxSecBetweenPresses = 0, lastPressSec = 0;
uint32_t count = 0;
bool dirty = false;  // flag for whether the screens need updating

void setup()
{
  Serial.begin(115200);
  pinMode(ButtonPin, INPUT_PULLUP);
  // initialize the LCD
  lcd.begin(16, 2);
  lcdB.begin(16, 2);
  lcdC.begin(16, 2);
  lcdD.begin(20, 4);

  // Turn on the blacklight and print a message.
  lcd.backlight();
  lcd.print("MaxTime btwn Presses");

  lcdB.backlight();
  lcdB.print("Uptime");
  lcdC.backlight();
  lcdC.print("Elapsed Betwn");
  lcdD.backlight();
  lcdD.print("Count:");
}

void loop()
{
  input();
  process();
  output();
}

void input() {
  const uint32_t interval = 1000;
  static uint32_t last = 0;
  static int lastButtonState = digitalRead(ButtonPin);
  int buttonState = digitalRead(ButtonPin);
  uint32_t now = millis();
  if (now - last >= interval) {
    last += interval;
    ++seconds;
    dirty = true;
  }
  if (buttonState != lastButtonState && now - lastChangeMs > 10) {
    lastButtonState = buttonState;
    lastChangeMs = now;
    if (lastButtonState == LOW) {
      lastPressMs = now;
      if (seconds - lastPressSec > maxSecBetweenPresses ) {
        maxSecBetweenPresses = seconds - lastPressSec;
      }
      lastPressSec = seconds;
      ++count;
    }
  }
}

void process() {};

void output() {
  if (dirty) {
    char buff[80];
    uint32_t secs = seconds;
    int days = 0, hours = 0, minutes = 0;
    //Serial.print(seconds); Serial.print("s ");
    dirty = false;
    // total elapsed
    days = seconds / 86400UL;
    hours = (seconds - days * 86400UL) / 3600;
    minutes = (seconds - days * 86400UL - hours * 3600UL) / 60;
    secs = (seconds - days * 86400UL - hours * 3600UL - minutes * 60UL);

    snprintf(buff, 80, "   %02d:%02d:%02d:%02d", days, hours, minutes, secs);
    lcdB.setCursor(0, 1);
    lcdB.print(buff);

    secs = seconds - lastPressSec;
    days = secs / 86400UL;
    secs -= days * 86400UL;
    hours = secs / 3600UL;
    secs -= hours * 3600UL;
    minutes = secs / 60UL;
    secs -= minutes * 60UL;

    snprintf(buff, 80, "   %02d:%02d:%02d:%02d ", days, hours, minutes, secs);
    lcdC.setCursor(0, 1);
    lcdC.print(buff);

    // count
    snprintf(buff, 80, "    %8ld", count);
    lcdD.setCursor(0, 1);
    lcdD.print(buff);

    secs = maxSecBetweenPresses;
    days = secs / 86400UL;
    secs -= days * 86400UL;
    hours = secs / 3600UL;
    secs -= hours * 3600UL;
    minutes = secs / 60UL;
    secs -= minutes * 60UL;

    snprintf(buff, 80, "   %02d:%02d:%02d:%02d", days, hours, minutes, secs);
    lcd.setCursor(0, 1);
    lcd.print(buff);
  }
};