// modified from https://wokwi.com/arduino/libraries/LiquidCrystal_I2C/HelloWorld
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 20, 4); // set the LCD address to 0x27 for a 16 chars and 2 line display

void setup()
{
  lcd.init();                      // initialize the lcd
  // Print a message to the LCD.
  lcd.backlight();
  lcd.setCursor(3, 0);
  lcd.print("Speed test");
  Serial.begin(115200);

  delay(1000);
}

void loop() {
  scrollLcd();
  LoopCounter();
}

void scrollLcd()
{
  const uint32_t interval = 2000;
  static uint32_t last;
  uint32_t now = micros();
  if (now - last >= interval) {
    last = now;

    static byte row = 0;
    static byte col = 0;
    static byte val = 0;
    lcd.setCursor(col, row);
    lcd.print((char)('0' + val));
    if (++col > 19) {
      col = 0;
      ++row;
    };
    if (row > 3) {
      row = 0;
      ++val;
    }
    if (val > 10 + 26 * 2) val = 0;
  }
}



void LoopCounter() // tells the average response speed of void loop()
// code modified from https://forum.arduino.cc/t/while-loop-as-a-condition-for-limit-switches/963899/11
{ // inside a function, static variables keep their value from run to run
  const unsigned long microsInOneSecond=1000000UL;
  static unsigned long count, countStartMicros; // only this function sees these

  count++; // adds 1 to count after any use in an expression, here it just adds 1.
  if ( micros() - countStartMicros >= microsInOneSecond ) // 1 second
  {
    countStartMicros += microsInOneSecond; // for a regular second
    Serial.println( count ); // 32-bit binary into decimal text = many micros
    count = 0; // don't forget to reset the counter 
  }
}