/*
  Simple 7 segment demo

  Written for common cathode
  In a real circuit the digit pin should have a transistor driver.
*/

const int SEG_PINS[] = {7, 8, 10, 11, 12, 6, 5, 9};
const bool DIGITS[][8] = {  // numeral lookup table
  // A  B  C  D  E  F  G  DP
  {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
  {0, 0, 0, 0, 0, 0, 0, 0}  // blank
};
const unsigned long ONE_SEC = 1000;

unsigned long prevTime = 0;

void writeDigit(int value) {
  for (int seg = 0; seg < 8; seg++) {
    digitalWrite(SEG_PINS[seg], DIGITS[value][seg]);
  }
}

void setup() {
  Serial.begin(115200);
  for (int segment = 0; segment < 8; segment++) {
    pinMode(SEG_PINS[segment], OUTPUT);
  }
}

void loop() {
  static int count = 0;

  // every ONE_SEC
  if (millis() - prevTime >= ONE_SEC) {
    count++;
    if (count > 10)  count = 0;
    prevTime = millis();
  }
  // refresh the display frequently
  writeDigit(count);
}