5.4 Serial Monitor and Serial Plotter

5.4.1 What is Serial Communication?

Serial communication is a method of transmitting data one bit at a time between electronic devices.

Arduino can use serial communication to exchange information with:

• A computer
• Another microcontroller
• Sensors
• GSM modules
• Bluetooth modules
• Other serial devices

Arduino IDE provides two important serial tools:

1. Serial Monitor
2. Serial Plotter

5.4.2 Serial Monitor

The Serial Monitor is a tool in the Arduino IDE that allows the user to view data sent from the Arduino to the computer and, when configured appropriately, send data from the computer back to the Arduino.

It is very useful for:

• Debugging programs
• Displaying sensor values
• Checking program execution
• Sending commands
• Monitoring system status

Starting Serial Communication

The Arduino program normally initializes serial communication using:

Serial.begin(9600);

Here, 9600 is the communication speed, called the baud rate.

Displaying Data

Serial.println(“Hello Arduino”);

The Arduino sends the message to the computer.

Simple Serial Monitor Program

void setup() {

  Serial.begin(9600);

}

 

void loop() {

  Serial.println(“Arduino is working”);

  delay(1000);

}

The Serial Monitor will display:

Arduino is working

Arduino is working

Arduino is working

Arduino is working

Serial Monitor Functions

Function	Purpose
Serial.begin()	Starts serial communication
Serial.print()	Prints data without a new line
Serial.println()	Prints data and moves to a new line
Serial.read()	Reads incoming serial data
Serial.available()	Checks whether data is available
Serial.write()	Sends raw byte data

 

5.4.3 Serial Monitor for Sensor Data

For example, a temperature sensor can send measurements to the Serial Monitor.

int temperature = 25;

 

void setup() {

  Serial.begin(9600);

}

 

void loop() {

  Serial.print(“Temperature: “);

  Serial.print(temperature);

  Serial.println(” C”);

 

  delay(1000);

}

Output:

Temperature: 25 C

Temperature: 25 C

Temperature: 25 C

5.4.4 Serial Plotter

The Serial Plotter is an Arduino IDE tool used to display changing numerical data as a graph over time.

It is particularly useful when working with:

• Sensors
• Temperature
• Light intensity
• Humidity
• Distance
• Sound
• Motor speed
• Voltage
• Analog signals

Example

int sensorValue;

 

void setup() {

  Serial.begin(9600);

}

 

void loop() {

 

  sensorValue = analogRead(A0);

 

  Serial.println(sensorValue);

 

  delay(100);

}

The Serial Plotter displays the changing sensor value as a graph.

Serial Plotter with Multiple Values

Multiple variables can also be sent to the Serial Plotter.

int temperature = 25;

int humidity = 60;

 

void setup() {

  Serial.begin(9600);

}

 

void loop() {

 

  Serial.print(“Temperature:”);

  Serial.print(temperature);

 

  Serial.print(“\t”);

 

  Serial.print(“Humidity:”);

  Serial.println(humidity);

 

  delay(500);

}

The Serial Plotter can then show separate lines representing the different values.