Pattern for Arduino LCD Keypad Shield

// Pattern for Arduino LCD Keypad Shield
// Create custom character: https://omerk.github.io/lcdchargen/
// String reference: https://www.arduino.cc/en/Reference/StringObject
// LCD reference: https://www.arduino.cc/en/Reference/LiquidCrystal
// Stream reference: http://playground.arduino.cc/Main/StreamingOutput

#include <LiquidCrystal.h>
#define TIMEOUT 10

LiquidCrystal lcd(8, 9, 4, 5, 6, 7);

void setup() {
  // Initialize Serial
  Serial.begin(9600);
  Serial.setTimeout(TIMEOUT);

  // Initialize LCD and special characters
  lcd.begin(16, 2);

  // Generate completely random
  randomSeed(analogRead(1));
}

void loop() {
  if (Serial.available() > 0) {

  }
}

char readKey() {
  short tolerance = 5;
  short value = analogRead(0);
  short values[] = {639, 408, 255, 99, 0};
  char out[]  = {'s', 'l', 'd', 'u', 'r'};
  for (int i = 0; i < 5; i++) {
    if (values[i] - tolerance < value && values[i] + tolerance > value) {
      return out[i];
    }
  }

  return '-';
}

String getRandomString(int n) {
    // Awful optimisation, but easy to scale
    char charset[] = "0123456789"
                     "abcdefghijklmnopqrstuvwxyz"
                     "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    String randomString = "";
    for (int i = 0; i < n; i++) {
      randomString += String(charset[random(0, strlen(charset))]);
    }
    return randomString;
}