How to read data from serial port correctly?

Question

Arduino

How can I properly process a string that is sent on a port? now the line looks like this

100%\n

, I pass the value of the processor, but I would also like to transfer another value, for example, RAM, if I pass it, everything is mixed into a heap, who has any options? I think that you need to add headers to the lines, something like this

CPU: 100%\n

, but how then to process it correctly in arudino a piece of code of the current firmware

char rx_byte = 0;
String rx_str = "";

void loop() {
  if (Serial.available() > 0) {
    rx_byte = Serial.read();
    
    if (rx_byte != '\n') {
      rx_str += rx_byte;
    }
    else {
    display.setTextSize(1);
    display.setTextColor(WHITE);
    display.setCursor(10,0);
   
    display.clearDisplay();
    display.println("Usage CPU - " + rx_str);
    rx_str = "";
    display.display();
                   
    }
  } 
}

Answer 1

1 byte - ID of the parameter (0x01 - CPU, 0x02 - RAM, etc.)
2 bytes - Value of the parameter
3 bytes - XOR between ID and Value
4 bytes - sign of the end of the transfer 0xFA, for example
Total transfer 4 bytes
On arduino:

int counter = 0;
if (Serial.available() > 0){
    rx_byte = Serial.read();
    if(rx_byte !=0xFA)
    {
        read_array[counter] = rx_byte
    }
    else
    {
     counter = 0;   
     if ((read_array[0] xor read_array[1])== read_array[3])
        {
        //данные приняты успешно, можно передавать в обработку
        }
        else
        {
        //данные искажены, не берем их в расчет
        } 
    }
}

The code is conditional, only to demonstrate the idea of ​​transmitting a packet with slightly better noise immunity than none.

Answer 2

What does "everything is mixed together" mean? You have \n as a line separator control character, you can pass as many parameters as you like in this format. At the end of the package, an end-of-package character, such as \f, is required. On the MK side, you need to provide a code that will separate the line. The code you provided does all this, but it doesn't take into account the possible passing of multiple parameters.