Make Arduino Rotating Clock Using Led Line

#include <Arduino.h>
#include <Wire.h>
#include <RTClib.h>
#include <Adafruit_NeoPixel.h>

// Forward declarations
void onMarker();
bool pixelForColumn(const uint8_t column, const uint8_t y, const uint8_t values[4]);
void showColumn(uint8_t phaseColumn);

constexpr uint8_t HALL_PIN = 2;
constexpr uint8_t LED_DATA_PIN = 6;
constexpr uint8_t LED_COUNT = 8; // Number of LEDs on the rotating arm, not a board pin.
constexpr uint8_t COLUMNS_PER_TURN = 120;
constexpr uint8_t GLYPH_HEIGHT = 5;
constexpr uint8_t DISPLAY_Y_OFFSET = 1;
constexpr uint8_t BRIGHTNESS = 32;

Adafruit_NeoPixel leds(LED_COUNT, LED_DATA_PIN, NEO_GRB + NEO_KHZ800);
RTC_DS3231 rtc;

volatile uint32_t markerMicros = 0;
volatile uint32_t previousMarkerMicros = 0;
volatile uint32_t revolutionMicros = 100000;
volatile bool markerSeen = false;

uint8_t lastColumn = 255;

const uint8_t digits[10][GLYPH_HEIGHT] = {
  {0b111, 0b101, 0b101, 0b101, 0b111},
  {0b010, 0b110, 0b010, 0b010, 0b111},
  {0b111, 0b001, 0b111, 0b100, 0b111},
  {0b111, 0b001, 0b111, 0b001, 0b111},
  {0b101, 0b101, 0b111, 0b001, 0b001},
  {0b111, 0b100, 0b111, 0b001, 0b111},
  {0b111, 0b100, 0b111, 0b101, 0b111},
  {0b111, 0b001, 0b010, 0b010, 0b010},
  {0b111, 0b101, 0b111, 0b101, 0b111},
  {0b111, 0b101, 0b111, 0b001, 0b111}
};

void onMarker() {
  const uint32_t now = micros();
  const uint32_t interval = now - markerMicros;
  // Ignore a second trigger from the same magnet pass and unreasonable speeds.
  if (interval > 20000UL && interval < 500000UL) {
    previousMarkerMicros = markerMicros;
    markerMicros = now;
    revolutionMicros = interval;
    markerSeen = true;
  } else if (markerMicros == 0) {
    markerMicros = now;
    markerSeen = true;
  }
}

bool pixelForColumn(const uint8_t column, const uint8_t y, const uint8_t values[4]) {
  // Each digit is 3 columns wide. The two separator dots occupy one column.
  uint8_t cursor = 0;
  for (uint8_t digitIndex = 0; digitIndex < 4; ++digitIndex) {
    if (digitIndex == 2) {
      if (column == cursor && (y == 1 || y == 3)) return true;
      ++cursor;
    }
    if (column >= cursor && column < cursor + 3) {
      const uint8_t bit = 2 - (column - cursor);
      return (digits[values[digitIndex]][y] & (1 << bit)) != 0;
    }
    cursor += 3;
    if (digitIndex != 3) ++cursor;
  }
  return false;
}

void showColumn(uint8_t phaseColumn) {
  // Put the 15-column HH:MM image in the middle of a 120-column turn.
  const int16_t imageColumn = static_cast<int16_t>(phaseColumn) - 52;
  leds.clear();

  if (imageColumn >= 0 && imageColumn < 15) {
    const DateTime now = rtc.now();
    const uint8_t values[4] = {
      static_cast<uint8_t>(now.hour() / 10),
      static_cast<uint8_t>(now.hour() % 10),
      static_cast<uint8_t>(now.minute() / 10),
      static_cast<uint8_t>(now.minute() % 10)
    };

    for (uint8_t y = 0; y < GLYPH_HEIGHT; ++y) {
      if (pixelForColumn(static_cast<uint8_t>(imageColumn), y, values)) {
        // Reverse if your physical strip is fitted with pixel 0 at the top.
        leds.setPixelColor(DISPLAY_Y_OFFSET + y, leds.Color(0, 0, BRIGHTNESS));
      }
    }
  }
  leds.show();
}

void setup() {
  pinMode(HALL_PIN, INPUT_PULLUP);
  attachInterrupt(digitalPinToInterrupt(HALL_PIN), onMarker, FALLING);

  Wire.begin();
  rtc.begin();
  if (rtc.lostPower()) {
    // Sets the RTC once from the firmware build time after a flat or missing coin cell.
    rtc.adjust(DateTime(__DATE__, __TIME__));
  }

  leds.begin();
  leds.setBrightness(BRIGHTNESS);
  leds.clear();
  leds.show();
}

void loop() {
  uint32_t markerCopy;
  uint32_t revolutionCopy;
  bool seenCopy;
  noInterrupts();
  markerCopy = markerMicros;
  revolutionCopy = revolutionMicros;
  seenCopy = markerSeen;
  interrupts();

  if (!seenCopy || revolutionCopy == 0) {
    return;
  }

  const uint32_t elapsed = micros() - markerCopy;
  if (elapsed >= revolutionCopy) {
    return; // Wait for the next Hall marker rather than drawing with a guessed angle.
  }

  const uint8_t column = static_cast<uint8_t>((elapsed * COLUMNS_PER_TURN) / revolutionCopy);
  if (column != lastColumn) {
    lastColumn = column;
    showColumn(column);
  }
}