lcdOKskeleton.ino

const int db4 = 13;
const int db5 = 12;
const int db6 = 11;
const int db7 = 10;
const int en = 9;
const int rs = 8;

void setup() {
  pinMode(db4, OUTPUT);
  pinMode(db5, OUTPUT);
  pinMode(db6, OUTPUT);
  pinMode(db7, OUTPUT);
  pinMode(rs, OUTPUT);
  pinMode(en, OUTPUT);

  initlcd();
    // Print 'G'
    sendMachineCode(1, 0, 1, 0, 0, 0, 1, 1, 1);
    // Print 'R'
    sendMachineCode(1, 0, 1, 0, 1, 0, 0, 1, 0);
  // Print 'E'
    sendMachineCode(1, 0, 1, 0, 0, 0, 1, 0, 1);
    // Print 'E'
    sendMachineCode(1, 0, 1, 0, 0, 0, 1, 0, 1);
  // Print 'N'
    sendMachineCode(1, 0, 1, 0, 0, 1, 1, 1, 0);

}

void loop() {

}

void send4bits(int rrs, int b7, int b6, int b5, int b4) {
  digitalWrite(rs, rrs);
  digitalWrite(db4, b4);
  digitalWrite(db5, b5);
  digitalWrite(db6, b6);
  digitalWrite(db7, b7);

  // Enable pulse
  digitalWrite(en, HIGH);
  delay(1);
  digitalWrite(en, LOW);
  delay(1);

}

void sendMachineCode(int rrs, int b7, int b6, int b5, int b4, int b3, int b2, int b1, int b0) {
  // Send higher nibble
  send4bits(rrs, b7, b6, b5, b4);
  // Send lower nibble
  send4bits(rrs, b3, b2, b1, b0);

}

void initlcd() {
  // Function set: 4-bit mode
  send4bits(0, 0, 0, 1, 0);
  // Now the LCD is in 4-bit mode, we can send full commands
  sendMachineCode(0, 0, 0, 0, 0, 0, 0, 0, 1); // Clear display
  sendMachineCode(0, 0, 0, 0, 0, 0, 0, 1, 0); // Return home
  sendMachineCode(0, 0, 0, 0, 0, 1, 1, 0, 0); // Display ON/OFF control: display on, cursor off, blink off
}