Serial Communication

Syntax#

Serial.begin(speed) // Opens the serial port on the given baud rate
Serial.begin(speed, config)
Serial[1-3].begin(speed) // Arduino Mega only! When writing 1-3 it means you can choose between the numbers 1 to 3 when choosing the serial port.
Serial[1-3].begin(speed, config) // Arduino Mega only! When writing 1-3 it means you can choose between the numbers 1 to 3 when choosing the serial port.
Serial.peek() // Reads the next byte of input without removing it from the buffer
Serial.available() // Gets the number of bytes in the buffer
Serial.print(text) // Writes text to the serial port
Serial.println(text) // Same as Serial.print() but with a trailing newline

Parameters#

Parameter	Details
Speed	The rate of the serial port (usually 9600)
Text	The text to write to the serial port (any data type)
Data bits	Number of data bits in a packet (from 5 - 8), default is 8
Parity	Parity options for error detection: none (default), even, odd
Stop bits	Number of stop bits in a packet: one (default), two
## Remarks#
The Arduino Mega has four serial ports which there can be choosed from. They are accesed in the following way

  Serial.begin(9600);
  Serial1.begin(38400);
  Serial2.begin(19200);
  Serial3.begin(4800);

The serial port on an Arduino can be set with additional parameters. The config parameter sets data bits, parity, and stop bits. For example:

8 data bits, even parity and 1 stop bit would be - SERIAL_8E1

6 data bits, odd parity and 2 stop bit would be - SERIAL_6O2

7 data bits, no parity and 1 stop bit would be - SERIAL_7N1

Simple read and write

This example listens for input coming in over the serial connection, then repeats it back out the same connection.

byte incomingBytes;

void setup() {                
  Serial.begin(9600); // Opens serial port, sets data rate to 9600 bps.
}

void loop() {
  // Send data only when you receive data.
  if (Serial.available() > 0) {
    // Read the incoming bytes.
    incomingBytes = Serial.read();

    // Echo the data.
    Serial.println(incomingBytes);
  }
}

Base64 filtering for serial input data

String base64="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";

void setup() {

    Serial.begin(9600); // Turn the serial protocol ON
    Serial.println("Start Typing");
}

void loop() {

    if (Serial.available() > 0) { // Check if data has been sent from the user
        char c = Serial.read();   // Gets one byte/Character from serial buffer
        int result = base64.indexOf(c); // Base64 filtering
        if (result>=0)
            Serial.print(c); // Only print Base64 string
    }
}

Command Handling over Serial

byte incoming;
String inBuffer;

void setup() {
    Serial.begin(9600); // or whatever baud rate you would like
}

void loop(){
    // setup as non-blocking code
    if(Serial.available() > 0) {
        incoming = Serial.read();
        
        if(incoming == '\n') {  // newline, carriage return, both, or custom character
        
            // handle the incoming command
            handle_command();

            // Clear the string for the next command
            inBuffer = "";
        } else{
            // add the character to the buffer
            inBuffer += incoming;
        }
    }

    // since code is non-blocking, execute something else . . . .
}

void handle_command() {
    // expect something like 'pin 3 high'
    String command = inBuffer.substring(0, inBuffer.indexOf(' '));
    String parameters = inBuffer.substring(inBuffer.indexOf(' ') + 1);
    
    if(command.equalsIgnoreCase('pin')){
        // parse the rest of the information
        int pin = parameters.substring("0, parameters.indexOf(' ')).toInt();
        String state = parameters.substring(parameters.indexOf(' ') + 1);

        if(state.equalsIgnoreCase('high')){
            digitalWrite(pin, HIGH);
        }else if(state.equalsIgnoreCase('low)){
            digitalWrite(pin, LOW);
        }else{
            Serial.println("did not compute");
        }
    } // add code for more commands 
}

Serial Communication with Python

If you have an Arduino connected to a computer or a Raspberry Pi, and want to send data from the Arduino to the PC you can do the following:

Arduino:

void setup() {
  // Opens serial port, sets data rate to 9600 bps:
  Serial.begin(9600);
}

void loop() {
  // Sends a line over serial:
  Serial.println("Hello, Python!");
  delay(1000);
}

Python:

import serial


ser = serial.Serial('/dev/ttyACM0', 9600)  # Start serial communication
while True:
    data = ser.readline()  # Wait for line from Arduino and read it
    print("Received: '{}'".format(data))  # Print the line to the console