sixty_second_counter.c

#include <Arduino.h>

struct BCD {
  int eights;
  int fours;
  int twos;
  int ones;
};

struct BCD decimal_to_BCD(int value) {
  switch (value)
  {
  case 0:
    /* code */
    return {0, 0, 0, 0};
  case 1:
    return {0, 0, 0, 1};
  case 2:
    return {0, 0, 1, 0};
  case 3:
    return {0, 0, 1, 1};
  case 4:
    return {0, 1, 0, 0};
  case 5:
    return {0, 1, 0, 1};
  case 6:
    return {0, 1, 1, 0};
  case 7:
    return {0, 1, 1, 1};
  case 8:
    return {1, 0, 0, 0};
  case 9:
    return {1, 0, 0, 1};
  default:
    break;
  }
}

int seconds = 0;

void increment_seconds() {
  seconds += 1;
  if (seconds >= 60) {
    seconds = 0;
  }
}

void write_seconds_ones_digit() {
  int ones_digit = seconds % 10;
  struct BCD bcd = decimal_to_BCD(ones_digit);

  digitalWrite(18, bcd.eights);
  digitalWrite(19, bcd.fours);
  digitalWrite(21, bcd.twos);
  digitalWrite(22, bcd.ones);
}

void write_seconds_tens_digit() {
  int tens_digit = seconds / 10;
  struct BCD bcd = decimal_to_BCD(tens_digit);

  digitalWrite(26, bcd.eights);
  digitalWrite(27, bcd.fours);
  digitalWrite(32, bcd.twos);
  digitalWrite(33, bcd.ones);
}

void setup() {
  Serial.begin(9600);

  // ones place
  pinMode(18, OUTPUT);
  pinMode(19, OUTPUT);
  pinMode(21, OUTPUT);
  pinMode(22, OUTPUT);

  // tens place
  pinMode(26, OUTPUT);
  pinMode(27, OUTPUT);
  pinMode(32, OUTPUT);
  pinMode(33, OUTPUT);
}

void loop() {
  increment_seconds();

  write_seconds_ones_digit();
  write_seconds_tens_digit();

  delay(1000);
}