arudino_7seg.c

const int pin_a  = 10;
const int pin_b  = 12;
const int pin_c  = 9;
const int pin_d  = 4;
const int pin_e  = 5;
const int pin_f  = 8;
const int pin_g  = 11;
const int pin_dp = 13;
const int dig1   = 2;
const int dig2   = 3;
const int dig3   = 6;
const int dig4   = 7;

const int all_pins[] = {pin_a, pin_b, pin_c, pin_d, pin_e, pin_f, pin_g, pin_dp, dig1, dig2, dig3, dig4};
const int all_pin_count = (sizeof(all_pins)/sizeof(int));
const int led_pins[] = {pin_a, pin_b, pin_c, pin_d, pin_e, pin_f, pin_g, pin_dp};
const int led_pin_count = (sizeof(led_pins)/sizeof(led_pins[0]));

const int slider_pin = 0;
const int ultrasonic_pin = 0;

long val;
int dig4_index;
int dig3_index;
int dig2_index;
int dig1_index;

typedef void (*FUNCPTR)();

FUNCPTR write_ptr[] = {&write_0, &write_1, &write_2, &write_3, &write_4, &write_5, 
                       &write_6, &write_7, &write_8, &write_9, &write_dp};

void setup() {
  for(int i = 0; i < all_pin_count; i++){
    pinMode(all_pins[i], OUTPUT);
  }
  
  dig_off();
}

void loop() {
  int bar_val = analogRead(slider_pin);

  if(bar_val == 0) {
    val = ultrasonic_read();
    dig4_index = (val%10); val/=10;
    dig3_index = (val%10); val/=10;
    dig2_index = (val%10); val/=10;
    dig1_index = (val%10); val/=10;  
  }

  use_dig1();
  write_ptr[dig1_index]();

  use_dig2();
  write_ptr[dig2_index]();

  use_dig3();
  write_ptr[dig3_index]();

  use_dig4();
  write_ptr[dig4_index]();
}

long ultrasonic_read() {
  pinMode(ultrasonic_pin, OUTPUT);
  digitalWrite(ultrasonic_pin, LOW);
  delayMicroseconds(2);
  digitalWrite(ultrasonic_pin, HIGH);
  delayMicroseconds(5);
  digitalWrite(ultrasonic_pin,LOW);
  pinMode(ultrasonic_pin,INPUT);
  long duration;
  duration = pulseIn(ultrasonic_pin,HIGH);
  long RangeInCentimeters;
  RangeInCentimeters = duration/29/2;
  return RangeInCentimeters;
}

void write_0() {
  const int pins[] = {pin_a, pin_b, pin_c, pin_d, pin_e, pin_f};
  write_7seg(led_pins, led_pin_count, LOW);
  write_7seg(pins, (sizeof(pins)/sizeof(pins[0])), HIGH);
  delay(1);
}

void write_1() {
  const int pins[] = {pin_b, pin_c};
  write_7seg(led_pins, led_pin_count, LOW);
  write_7seg(pins, (sizeof(pins)/sizeof(pins[0])), HIGH);
  delay(1);
}

void write_2() {
    const int pins[] = {pin_a, pin_b, pin_d, pin_e, pin_g};
  write_7seg(led_pins, led_pin_count, LOW);
  write_7seg(pins, (sizeof(pins)/sizeof(pins[0])), HIGH);
  delay(1);
}

void write_3() {
  const int pins[] = {pin_a, pin_b, pin_c, pin_d, pin_g};
  write_7seg(led_pins, led_pin_count, LOW);
  write_7seg(pins, (sizeof(pins)/sizeof(pins[0])), HIGH);
  delay(1);
}

void write_4() {
  const int pins[] = {pin_b, pin_c, pin_f, pin_g};
  write_7seg(led_pins, led_pin_count, LOW);
  write_7seg(pins, (sizeof(pins)/sizeof(pins[0])), HIGH);
  delay(1);
}

void write_5() {
  const int pins[] = {pin_a, pin_c, pin_d, pin_f, pin_g};
  write_7seg(led_pins, led_pin_count, LOW);
  write_7seg(pins, (sizeof(pins)/sizeof(pins[0])), HIGH);
  delay(1);
}

void write_6() {
  const int pins[] = {pin_a, pin_c, pin_d, pin_e, pin_f, pin_g};
  write_7seg(led_pins, led_pin_count, LOW);
  write_7seg(pins, (sizeof(pins)/sizeof(pins[0])), HIGH);
  delay(1);
}

void write_7() {
  const int pins[] = {pin_a, pin_b, pin_c, pin_f};
  write_7seg(led_pins, led_pin_count, LOW);
  write_7seg(pins, (sizeof(pins)/sizeof(pins[0])), HIGH);
  delay(1);
}

void write_8() {
  const int pins[] = {pin_a, pin_b, pin_c, pin_d, pin_e, pin_f, pin_g};
  write_7seg(led_pins, led_pin_count, LOW);
  write_7seg(pins, (sizeof(pins)/sizeof(pins[0])), HIGH);
  delay(1);
}

void write_9() {
  const int pins[] = {pin_a, pin_b, pin_c, pin_d, pin_f, pin_g};
  write_7seg(led_pins, led_pin_count, LOW);
  write_7seg(pins, (sizeof(pins)/sizeof(pins[0])), HIGH);
  delay(1);
}

void write_dp() {
  const int pins[] = {pin_dp};
  write_7seg(led_pins, led_pin_count, LOW);
  write_7seg(pins, (sizeof(pins)/sizeof(pins[0])), HIGH);
  delay(1);
}

void use_dig1() {
  dig_off();
  digitalWrite(dig1, LOW);
}

void use_dig2() {
  dig_off();
  digitalWrite(dig2, LOW);
}

void use_dig3() {
  dig_off();
  digitalWrite(dig3, LOW);
}

void use_dig4() {
  dig_off();
  digitalWrite(dig4, LOW);
}

void dig_off() {
  digitalWrite(dig1, HIGH);
  digitalWrite(dig2, HIGH);
  digitalWrite(dig3, HIGH);
  digitalWrite(dig4, HIGH);
}

void write_7seg(const int pattern[], int index, int value) {
  for(int i = 0; i < index; i++) {
    digitalWrite(pattern[i], value);
  }