Serial Monitor

Objectives and Overview

This lesson introduces the serial monitor. This tool helps monitor input and output values by listening to communication to and from the Arduino board.

Lesson Objectives

• Understand and explain the purpose of the serial monitor and give an example of the information it provides.
• Demonstrate that you’re able to display the serial monitor in a sketch.

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The Serial Monitor

Now that you’ve been adding inputs to your Arduino, it would be useful to be able to have a method for monitoring the information that is being sent from the inputs. In the previous project, the photoresistor constantly sends information based on the light level in the room. You then mapped the values being sent from the photoresistor to the LED brightness. However, these values have been “hidden” from you in the sense that they are essentially passing from component to component.

This is fine as long as your project is working as intended, but sometimes it’s helpful to see the values that the Arduino is reading. In the previous example, it would’ve been useful to actually monitor the range of values that the Arduino reads from the photoresistor.

Arduino has a feature called the serial console for this purpose. This console is built into the Uno that you’re using in this course. There are other Arduino boards with this feature, but it’s important to note that not every board supports serial output.

Basically, the serial monitor is used to listen to the communication between the Arduino board and a computer.

For this project, you’ll be using the circuit setup from the previous photoresistor project. Adding the serial monitor is done in the Arduino IDE, so for this project, there is no need to change your connections.

Code Additions

Note: This example will be using the code from the potentiometer sketch.

There is some code that you need to add in order to use the serial monitor. Let’s build it out step by step:

In void setup(), add the following line of code: Serial.begin(9600);
Your setup should look like this:

void setup() {
pinMode(ledPin, OUTPUT); // configure the ledPin for output
Serial.begin(9600);
}
Code language: JavaScript (javascript)

In void loop(), add the following code after potentValue:

Serial.print("Analog Read"); // outputs to the serial console
Serial.println(potentValue); // outputs potentValue to serial console and adds a new line at the end
Code language: PHP (php)

The void loop() should now look like this:

void loop() {
  // put your main code here, to run repeatedly:
  potentValue=analogRead(potentPin); // read the value of the potentiometer pin
  Serial.print("Analog Read: "); // output to serial console
  Serial.println(potentValue); // output potentValue to serial console and add a new line at the end
  brightnessValue=map(potentValue,0,1023,0,255); // map the potentiometer value to a brightness
  analogWrite(ledPin,brightnessValue); // set the brightness of the ledPin
}
Code language: JavaScript (javascript)

The complete sketch should look like this:

int ledPin=0; // variable to store the LED pin
int potentPin=0; // variable to store potentiometer pin
int potentValue=0; // variable to store last known value of potentiometer
int brightnessValue=0; // variable to store LED brightness
 
void setup() {
  pinMode(ledPin, OUTPUT); // configure the LED pin for output
  Serial.begin(9600);
}
 
void loop() {
  potentValue=analogRead(potentPin); // read the value of the potentiometer pin
  Serial.print("Analog Read: "); // output to serial console
  Serial.println(potentValue); // output potentValue to serial console and add a new line at the end
  brightnessValue=map(potentValue,0,1023,0,255); // map the potentiometer value to a brightness
  analogWrite(ledPin,brightnessValue); // set the brightness of the ledPin
}
Code language: JavaScript (javascript)

New Commands

This project introduced three new commands: Serial.begin(), Serial.print(), and Serial.println(). Let’s review each command before moving to the next project.

• Serial.begin(): This sets up the data rate for the serial connection. The typical value that you’ll use is 9600. This number needs to match the value in the Serial Monitor window or else it won’t work.
• Serial.print(): This is the command that actually prints to the serial port.
• Serial.println(): This command prints to the serial port and is followed by a new line. In the example code, this is the command that prints and then creates a space after the entry.

Quick Test: Go ahead and change the Serial.println() in the code to be Serial.print() and see what happens!