Arduino program to control an 8 relay board from a Serial connection

serial8RelayBoardControl.imo

// Takes an input from Serial (11111110) and turns on 1-7 relays and turns off relay 8.

// the setup function runs once when you press reset or power the board
void setup() {
  pinMode(2, OUTPUT);
  pinMode(3, OUTPUT);
  pinMode(4, OUTPUT);
  pinMode(5, OUTPUT);
  pinMode(6, OUTPUT);
  pinMode(7, OUTPUT);
  pinMode(8, OUTPUT);
  pinMode(9, OUTPUT);
  digitalWrite(2, HIGH);
  digitalWrite(3, HIGH);
  digitalWrite(4, HIGH);
  digitalWrite(5, HIGH);
  digitalWrite(6, HIGH);
  digitalWrite(7, HIGH);
  digitalWrite(8, HIGH);
  digitalWrite(9, HIGH);
  Serial.begin(9600);
}

// Array of relay board pins
char currentPins[8] = {'0', '0', '0', '0', '0', '0', '0', '0'};

// Used to store input from serial connection (eg. 11111111) (all on)
char inputStr[8];

// the loop function runs over and over again forever
void loop() {
  while (Serial.available() == 0) {}     //wait for data available
  int inputLength = Serial.readBytesUntil('\n', inputStr, 9);  //read until timeout

  if (inputLength != 8) {
    Serial.println("ERR_LEN");
    return;
  }

  for (int i = 0; i < inputLength; i++) {
    if (inputStr[i] != '0' && inputStr[i] != '1') {
      Serial.println("ERR_CHAR");
      return;
    }
  }

  for (int i = 0; i < inputLength; i++) {
    if (currentPins[i] == inputStr[i]) {
      continue;
    }

    const int pin = i + 2;
    if (inputStr[i] == '0') {
      digitalWrite(pin, HIGH);
    } else {
      digitalWrite(pin, LOW);
    }

    currentPins[i] = inputStr[i];
  }

  Serial.println("DONE");
}