//----------------------------------
#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x27,16,2);           // select the pins used on the LCD panel

const byte numBytes = 255;
char line1[numBytes];
char line2[numBytes];
byte line1b = 0;
byte line2b = 0;
//----------------------------------
int Li          = 16;
int Lii         = 0;
int Ri          = -1;
int Rii         = -1;
//----------------------------------
void setup(){
  lcd.init();                           // start the LCD library
  lcd.backlight();
  Serial.begin(9600);
}
//----------------------------------

void loop(){

  processdata();

  lcd.setCursor(0,1);
  lcd.print(line2);
  lcd.setCursor(0, 0);
  lcd.print(Scroll_LCD_Left(line1));
  delay(250);
  if(Lii==1) {delay(2000);} //wait 2 seconds before starting scroll

}

//----------------------------------
String Scroll_LCD_Left(String StrDisplay){
  String result;
  if (StrDisplay.length() < 17) { // why scroll if we're under 16 characters?
    result = StrDisplay;
    return result;
  }
  String StrProcess = StrDisplay + "                ";
  result = StrProcess.substring(Li,Lii);
  Li++;
  Lii++;
  if (Li>StrProcess.length()){
    Li=16;
    Lii=0;
  }
  return result;
}

void Clear_Scroll_LCD_Left(){
  Li=16;
  Lii=0;
}
void processdata() {
    int ndx = 0;
    byte startMarker = 0x02;
    char linebreak = '\n';
    byte endMarker = 0x04;
    char rb;
    int topline;

topline = 1;
    while (Serial.available() > 0) {
        rb = Serial.read();
        if (topline == 1) {
             if (rb == linebreak) {
                line1[ndx] = '\0';
                line1b = ndx;
                topline = 0;
                ndx=0;
                Clear_Scroll_LCD_Left();
             }
             else {
              line1[ndx] = rb;
              ndx++;
             }
                          }

        else  {
              if (rb == linebreak) {
                line2[ndx] = '\0';
                line2b = ndx;
                Serial.flush();
                clearLCDbuffer();

              }
              else {
                line2[ndx] = rb;
                ndx++;
              }
              }}

       }

void clearLCDbuffer() {
    lcd.setCursor(0,0);
    lcd.print("                ");
    lcd.setCursor(0,1);
    lcd.print("                ");
}