How to Parse Serial Data in Arduino: Simple Guide

To parse serial data in Arduino, use Serial.available() to check if data is ready, then read it with Serial.read() or Serial.readStringUntil(). You can convert the received data into usable values by splitting strings or using functions like toInt().

Syntax

Here are the main functions to read serial data in Arduino:

• Serial.available(): Returns the number of bytes available to read.
• Serial.read(): Reads one byte (character) from the serial buffer.
• Serial.readStringUntil(char terminator): Reads characters until the terminator is found.

You use these to check for incoming data and then read it for parsing.

arduino

if (Serial.available() > 0) {
  char incomingByte = Serial.read();
  // process incomingByte
}

String data = Serial.readStringUntil('\n'); // reads until newline character

Example

This example reads a line of serial data ending with a newline, splits it by commas, and converts each part to an integer.

arduino

void setup() {
  Serial.begin(9600);
  while (!Serial) { ; }
  Serial.println("Send numbers separated by commas, e.g. 10,20,30");
}

void loop() {
  if (Serial.available()) {
    String input = Serial.readStringUntil('\n');
    int values[3];
    int index = 0;
    int start = 0;
    for (int i = 0; i <= input.length(); i++) {
      if (input.charAt(i) == ',' || i == input.length()) {
        String part = input.substring(start, i);
        values[index++] = part.toInt();
        start = i + 1;
      }
    }
    Serial.print("Parsed values: ");
    for (int i = 0; i < index; i++) {
      Serial.print(values[i]);
      Serial.print(" ");
    }
    Serial.println();
  }
}

Output

Send numbers separated by commas, e.g. 10,20,30
Parsed values: 10 20 30 

Common Pitfalls

Common mistakes when parsing serial data include:

• Not checking Serial.available() before reading, which can cause errors.
• Assuming all data arrives at once; serial data can come slowly and in parts.
• Not handling the end of data properly, like missing newline terminators.
• Using Serial.read() without converting bytes to the correct data type.

Always wait for complete data and parse carefully.

arduino

/* Wrong way: reading without checking availability */
if (Serial.available() > 0) {
  char c = Serial.read();
  // process c
}

/* Right way: */
if (Serial.available() > 0) {
  char c = Serial.read();
  // process c
}

Quick Reference

Function	Description
Serial.available()	Returns number of bytes available to read
Serial.read()	Reads one byte from serial buffer
Serial.readStringUntil(char)	Reads characters until the specified terminator
String.toInt()	Converts string to integer
String.substring(start, end)	Extracts part of a string

Key Takeaways

Always check Serial.available() before reading serial data.

Use Serial.readStringUntil() to read complete lines ending with a terminator.

Parse the received string by splitting and converting parts to needed data types.

Handle incomplete or slow serial data carefully to avoid errors.

Convert bytes or strings properly to integers or other types before use.