[SMT Part Counter](https://hackaday.io/project/27910-smt-part-tape-counter)

smtPartCounter.ino

#include "TimerOne.h"

const int PIN_1_K = 10;
const int PIN_2_K = 12;
const int PIN_3_K = 11;

int digits[10][8] = {
 // 0  1  2  3  4  5  6  7
  { 1, 1, 0, 1, 0, 1, 1, 1 }, // 0
  { 0, 0, 0, 1, 0, 1, 0, 0 }, // 1
  { 1, 1, 0, 0, 1, 1, 1, 0 }, // 2
  { 0, 1, 0, 1, 1, 1, 1, 0 }, // 3
  { 0, 0, 0, 1, 1, 1, 0, 1 }, // 4
  { 0, 1, 0, 1, 1, 0, 1, 1 }, // 5
  { 1, 1, 0, 1, 1, 0, 1, 1 }, // 6
  { 0, 0, 0, 1, 0, 1, 1, 0 }, // 7
  { 1, 1, 0, 1, 1, 1, 1, 1 }, // 8
  { 0, 0, 0, 1, 1, 1, 1, 1 }  // 9
};

volatile bool disableDigits = false;
volatile int digit1 = 1;
volatile int digit2 = 2;
volatile int digit3 = 3;

void setup() {
  Serial.begin(115200);

  pinMode(2, OUTPUT);
  pinMode(3, OUTPUT);
  pinMode(4, OUTPUT);
  pinMode(5, OUTPUT);
  pinMode(6, OUTPUT);
  pinMode(7, OUTPUT);
  pinMode(8, OUTPUT);
  pinMode(9, OUTPUT);

  pinMode(A0, INPUT_PULLUP);
  pinMode(A1, INPUT_PULLUP);

  Timer1.initialize(100);
  Timer1.attachInterrupt(refresh);
}

void displayDigit(uint8_t n) {
  int *segments = digits[n];

  for (int i = 0; i < 8; i++) {
    digitalWrite(2 + i, segments[i]);
  }
}

uint8_t count = 0;
void refresh() {
  if (disableDigits) {
    pinMode(PIN_1_K, INPUT);
    pinMode(PIN_2_K, INPUT);
    pinMode(PIN_3_K, INPUT);
    return;
  }
  
  uint8_t v = (count >> 4) % 3;
  
  if (v == 0) {
    pinMode(PIN_3_K, INPUT);
    pinMode(PIN_1_K, OUTPUT);
    displayDigit(digit1);
  } else if (v == 1) {
    pinMode(PIN_1_K, INPUT);
    pinMode(PIN_2_K, OUTPUT);
    displayDigit(digit2);
  } else if (v == 2) {
    pinMode(PIN_2_K, INPUT);
    pinMode(PIN_3_K, OUTPUT);
    displayDigit(digit3);
  }

  count++;
}

void setDigits(int v) {
  digit1 = v / 100 % 10;
  digit2 = v / 10 % 10;
  digit3 = v % 10;
}

void loop() {
  static int multiplier = 1;
  static int multiplierShowCounter = 0;
  static int count = 0;
  static bool wasHigh = false;

  if (!digitalRead(A0)) {
    count = 0;
  }

  if (!digitalRead(A1)) {
    multiplier++;
    if (multiplier > 3) {
      multiplier = 1;
    }

    multiplierShowCounter = 100;
    disableDigits = true;
    delay(100);
    disableDigits = false;
    setDigits(multiplier);
    delay(100);
  }

  if (digitalRead(A2)) {
    if (!wasHigh) {
      count++;
      wasHigh = true;
    }
  } else {
    if (wasHigh) {
      wasHigh = false;
    }
  }

  if (multiplierShowCounter == 0) {
    setDigits(count * multiplier);
  } else {
    multiplierShowCounter--;
    delay(10);
  }
}