Using Arduino Serial Monitor From Linux

Arduino Serial Monitor is a tool that can be used for debugging or interacting with our Arduino board. More specifically, it allows us to read and write data to a serial port.

For our sketch to be able to use the serial monitor, we need to use Serial.begin and specify a baud rate. For example:

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Serial.begin(9600);

The valid baud rates vary depending on the board we are using. 9600 is a safe value that works on most boards.

Reading

The first thing we want to do is print to the serial port. For example:

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Serial.println("Hello");

This simple sketch shows how we can print a Hello message every 2 seconds:

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void setup() {
  Serial.begin(9600);
}

void loop() {
  Serial.println("Hello");
  delay(2000);
}

If we upload this sketch to our board and connect the board to our PC, we can use these commands to see the output of our sketch:

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sudo chmod a+rw /dev/ttyACM0
sudo stty 9600 -F /dev/ttyACM0 raw -echo
sudo cat /dev/ttyACM0

Note that 9600 matches the baud rate specified in our sketch.

Writing

We can also use our board’s serial port to receive input from users. There are multiple functions available for reading data; I’ll use parseInt() in my example, since it’s very easy to use:

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int inputNumber;

void setup() {
  Serial.begin(9600);
}

void loop() {
  Serial.println("Enter a number:");

  while (Serial.available() == 0) {
    // Loop until there is data to be read
  }

  inputNumber = Serial.parseInt();
  Serial.print("You entered: ");
  Serial.println(inputNumber);
}

We use Serial.available to wait for the user to input some data. To input said data, we can use these commands:

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sudo chmod a+rw /dev/ttyACM0
sudo stty 9600 -F /dev/ttyACM0 raw -echo
echo "45" > /dev/ttyACM0

Conclusion

Arduino IDE includes a Serial Monitor that can be used to interact with a board’s serial port. In Linux environments we can use commands available in most distributions to interact with the serial port even if Arduino IDE is not available.