Do you remember the magnifying glass icon in the upper right corner of your sketch window? Clicking on it opens the Serial Monitor – provided your Arduino UNO is connected to your computer and you have selected the correct USB port.
The Serial Monitor functions as a communication interface for your Arduino. It can display measurement values and other data, allowing you to check them. But this interface also works in the other direction – you can send commands to your Arduino through the Serial Monitor.
Let’s first take a look at the most important parts of the monitor:
In the top right, you’ll find three buttons:
- Autoscroll: The Serial Monitor scrolls along with the incoming data – the newest entry is always visible at the bottom.
- Timestamp: The data is marked with the exact time of its arrival.
- Clear Output: All entries in the monitor are deleted.
To the left of these buttons, you’ll find an input field. This allows you to send data and commands to your Arduino. For now, however, we’ll focus on reading data.
The largest part of the window is reserved for output – this is where you’ll display text in the next lesson.
The Baud Rate
The baud rate (or symbol rate) refers to the number of characters transmitted per second. Projects with an Arduino UNO often use a rate of 9,600.
If you open the dropdown menu, you’ll see many other baud rates available. These will become relevant if you later build projects with an ESP8266 or ESP32, as these microcontrollers are significantly faster than an Arduino UNO.
One thing is important: This dropdown menu must always be set to the same baud rate as in your sketch (you’ll learn how to set it there in the next lesson). If the baud rates in the sketch and monitor differ, nothing will break – but you’ll often see a jumble of characters. 😉
One more note: Your Arduino can communicate not only via USB but also via pins 0->RX and 1<-TX. Therefore, you shouldn’t connect anything to these pins unless you specifically want to use them for serial communication later.
In the next lesson, you’ll get practical experience by activating the Serial Monitor and displaying your first characters there.