Simple sketch to drive the resistor ladder circuit.

ladder.ino

const byte D0 = 44; // Digital Line 0
const byte D1 = 45; // Digital Line 1
const byte D2 = 46; // Digital Line 2

void setup() {
  pinMode(D0, OUTPUT);
  pinMode(D1, OUTPUT);
  pinMode(D2, OUTPUT);
}

void loop() {
  digitalWrite(D0, LOW);
  digitalWrite(D1, LOW);
  digitalWrite(D2, LOW);
  delay(2);
  digitalWrite(D0, LOW);
  digitalWrite(D1, LOW);
  digitalWrite(D2, HIGH);
  delay(2);
  digitalWrite(D0, LOW);
  digitalWrite(D1, HIGH);
  digitalWrite(D2, LOW);
  delay(2);
  digitalWrite(D0, LOW);
  digitalWrite(D1, HIGH);
  digitalWrite(D2, HIGH);
  delay(2);
  digitalWrite(D0, HIGH);
  digitalWrite(D1, LOW);
  digitalWrite(D2, LOW);
  delay(2);
  digitalWrite(D0, HIGH);
  digitalWrite(D1, LOW);
  digitalWrite(D2, HIGH);
  delay(2);
  digitalWrite(D0, HIGH);
  digitalWrite(D1, HIGH);
  digitalWrite(D2, LOW);
  delay(2);
  digitalWrite(D0, HIGH);
  digitalWrite(D1, HIGH);
  digitalWrite(D2, HIGH);
  delay(2);
}