// https://forum.arduino.cc/t/help-with-tm1637-6-digit-and-button/1416196/279
// https://wokwi.com/projects/450964521677860865

const int N = 2 ;  // display width

// Pin definitions for 7-segment display chosen for ease of routing in Wokwi
const int segmentPins[] = {7, 8, 6, 3, 4, 11, 2, 5};    // A, B, C, D, E, F, G, DP
const int digitPins[N] = {9, 10};                      // Digit 1 (tens), Digit 2 (units)

// This matches 1:1 what appears on the display say show seconds 00 to 59
volatile byte displayImage[N] ;


// 7-segment display patterns for digits 0-9 (common cathode)
// Format: {A, B, C, D, E, F, G, DP}
const byte digitPatterns[10][8] = {
  {1, 1, 1, 1, 1, 1, 0, 0}, // 0
  {0, 1, 1, 0, 0, 0, 0, 0}, // 1
  {1, 1, 0, 1, 1, 0, 1, 0}, // 2
  {1, 1, 1, 1, 0, 0, 1, 0}, // 3
  {0, 1, 1, 0, 0, 1, 1, 0}, // 4
  {1, 0, 1, 1, 0, 1, 1, 0}, // 5
  {1, 0, 1, 1, 1, 1, 1, 0}, // 6
  {1, 1, 1, 0, 0, 0, 0, 0}, // 7
  {1, 1, 1, 1, 1, 1, 1, 0}, // 8
  {1, 1, 1, 1, 0, 1, 1, 0}  // 9
};


void setup() {
  Serial.begin(115200);
  Serial.println("\nhi Mom!\n");

  // test data
  displayImage[0] = 4 ;
  displayImage[1] = 6 ;

  for (int i = 0; i < 8; i++) pinMode(segmentPins[i], OUTPUT ) ;   // segments
  for (int i = 0; i < N; i++) pinMode(digitPins[i], OUTPUT) ; // commons

  cli();

  // Reset Timer1 control registers
  TCCR1A = 0;
  TCCR1B = 0;
  TCNT1 = 0;

  OCR1A = 249;  // Compare match value for 4ms
  TCCR1B |= (1 << WGM12);  // Turn on CTC mode (Clear Timer on Compare Match)
  TCCR1B |= (1 << CS12);  // Set prescaler to 256
  TIMSK1 |= (1 << OCIE1A);  // Enable timer compare interrupt

  sei() ;

}

// we really don't need to do anything in the loop
void loop0(){}


int counter;
int speed;

void loop()
{
  static unsigned long lastIncrement;
  unsigned long now = millis();

  int reading = analogRead(A0);
  speed = map(reading, 0, 1023, 200, 0);

  if (now - lastIncrement < 2000) return;
  
  lastIncrement = now;
  counter++;

  noInterrupts();
  displayImage[1] = counter % 10;
  displayImage[0] = (counter / 10) % 10;
  interrupts();

  Serial.print(displayImage[0]); Serial.print("  ");
  Serial.print(displayImage[1]); Serial.println("");
}

ISR(TIMER1_COMPA_vect) 
{
  static byte skipper;
  if (skipper++ < speed) return;
  skipper = 0;

// called every say 4 ms from timer1
  static byte currentSegment = 0;
  if (++currentSegment == 7) currentSegment = 0;

  digitalWrite(digitPins[0], HIGH); // turn off digits to prevent ghosting
  digitalWrite(digitPins[1], HIGH); // turn off digits to prevent ghosting

  for (int seg = 0; seg < 8; seg++)
    digitalWrite(segmentPins[seg], LOW);

  digitalWrite(segmentPins[currentSegment], HIGH);

  for (int dig = 0; dig < N; dig++) {
    int digitValue = displayImage[dig];

    if (digitPatterns[digitValue][currentSegment]) digitalWrite(digitPins[dig], LOW);
  } 
}