/*

  Forum: https://forum.arduino.cc/t/reading-hex-binary-from-pc-serial-then-output/1302803/9
  Wokwi: https://wokwi.com/projects/409852867075662849

  Copy one of the following lines to Serial input and press return to test the routines:

  01234567890123456789<#This part is okay #>
  Test<- This part is okay->EndOfTest
  01234567890123456789<A01234567890123456GFGFGF>
  01234567890123456789<This part is okay !!>01234567890123456789<A01234567890123456GFGFGF>

  Be aware that < and > are used as START and STOPCHARACTER.
  There must be exactly messageLen characters between these brackets to be considered a valid
  message.

*/

#include <LiquidCrystal_I2C.h>
#define I2C_ADDR    0x27
#define LCD_COLUMNS 20
#define LCD_LINES   4
LiquidCrystal_I2C lcd(I2C_ADDR, LCD_COLUMNS, LCD_LINES);

const byte STARTCHARACTER = '<';  // Replace by 0x1B
const byte STOPCHARACTER = '>';   // Replace by 0x12
const byte bufferLen  = 21;       // Allows to read more than the message length to detect length errors
const byte messageLen = 20;       // This is the length of a valid message

byte msg[bufferLen]; //byte array to store values not including the STOPCHARACTER
int bytesRead = 0;   // Counts the numbers of bytes read
boolean msgBegin = false;   // Becomes true if STARTCHARACTER was recveived
boolean msgFound = false;   // Becomes true if a valid message was found
// means: messageLen characters between START- and STOPCHARACTER
boolean error  = false;     // Becomes true if more or less that messageLen characters were received
// between START- and STOPCHARACTER

void setup() {
  setupLCD();
  Serial.begin(115200); // opens input serial port, sets data rate to 1115200 bps
  Serial.println("Start");
}

void loop() {
  if (Serial.available() > 0) { // check if data is available
    byte aChar = Serial.read();
    if (aChar == STOPCHARACTER) {
      msgBegin = false;
      msgFound = (bytesRead == messageLen);
      error = !msgFound;
      bytesRead = 0;
    }
    if (msgBegin && bytesRead < bufferLen) {
      msg[bytesRead] = aChar;
      bytesRead++;
    }
    if (aChar == STARTCHARACTER) {
      msgBegin = true;
      bytesRead = 0;
    }
  }
  if (msgFound) {
    writeToLCD();
    msgFound = false;
  }
  if (error) {
    Serial.println("Wrong message length");
    error = false;
  }
}

void setupLCD() {
  lcd.init();
  lcd.backlight();
}

void writeToLCD() {
  Serial.println("Message found!");
  lcd.clear();
  lcd.print("STX");
  lcd.print("0");
  lcd.print("1");
  lcd.setCursor(0, 1);
  for (int i = 0; i < messageLen; i++) {
    lcd.print(char(msg[i]));
  }
  lcd.setCursor(0, 2);
  lcd.print("ETX");
}