The Serial Monitor Window

You can use the Serial Monitor Window to send data via the serial connection to your Arduino board and to visualize incoming data from your board.

With the Serial.print() and Serial.read() functions, you can send and receive data via the serial port. Visual Micro's Serial Monitor is the PCs counterpart on the other end of the serial line.

You can find the documentation of the Serial... functions on the Arduino web site.

To show the Serial Monitor in your IDE, choose Tools > Visual Micro > Serial Monitor or click the Serial Monitor button in the Arduino Communications toolbar:

Serial Monitor Toolbar Button

With the selection box COM Port Selection you choose the COM port your board is connected to.

Note

A good start for experimenting with Arduino's Serial functions is the ReadASCIIString example provided by the classic Arduino IDE.

Anatomy of the Serial Monitor window

Sending and receiving data

Serial Monitor (1)

In the Outbound Area you can enter characters. As soon as you click on the Send Button, the string is sent to your Arduino board and can be received by the board via a Serial.Read() function.

Strings sent by your Arduino board are displayed in the Inbound Area.

Settings and other functions

The other elements of the Serial Monitor window are important to configure and control the serial connection.

Serial Monitor (2)

Connection Checkbox

If you uncheck this box, the connection to your board will be interrupted. The serial port is then free for other programs on your PC.
If you check that box again, the connection will be restored. The behavior of your Arduino board depends on the DTR checkbox (see below).

DTR Switch

The DTR line of your board's UART is used to reset the board and restart the sketch. If this box is checked, Visual Micro controls the DTR line which results in a board reset if the board connection is established/restored (with the "Connect" box above). The DTR switch has no effect if you use SoftwareSerial as the transport method, see "Advanced Serial Communication". The DTR switch also has no effect with some sorts of boards that have a separate small processor for serial communications.

"Clear" Checkbox

Check this box to clear the contents of the Inbound box where the data sent by the Arduino board is shown.
When this box is checked, the inbound area of the window will be cleared every time the port is reopened.

"Reconnect" Switch

Indicates whether Visual Micro attempts to reconnect to the board once it was disconnected. The initial state of this switch is taken from Tools > Options > Communications > Auto Re-Connect.

Echo Settings

This setting can be used to route all incoming data from one board to another board connected to a different COM port.
Example: If you have two boards attached to your PC, one on COM3 and one on COM4, and you choose "COM4" in the Serial Monitor of COM3, then all data coming in from COM3 will be displayed in the Serial Monitor and sent to the other board via COM4.

Line End Settings

Specifies how the string is terminated that you send to your Arduino board after clicking the Send Button.

"no line endings": no character is appended to the string being sent.
"Carriage return": a Carriage return character ('CR'=0x0d or '\r') is appended .
"Newline": a newline aka Line Feed character ('LF'=0x0a or '\n') is appended .
"Both NL and CR": both a CR and a newline (LF) character are appended .

The right setting depends on how your sketch handles the incoming characters. In the Arduino ReadASCIIString example, you will notice that the sketch waits for a '\n', which is a "newline" or "line feed". So for this sketch, the "Newline" setting will be the right one. If in doubt, use the "Both NL and CR" setting.

Baud Rate Settings

Specifies the transmission speed or so called "baud rate" that Visual Micro and your board use. This setting must match the setting your sketch uses in the Serial.begin() function. In the Arduino ReadASCIIString example, the sketch operates with a setting of 9600.
If the baud rate of your board and that of Visual Micro don't match, you will see no incoming characters or garbage only.
If you are using Visual Micro debugging, then this value must also match the baud rate setting you chose for debugging communication, see "Debugging with Different Ports, Pins and Speeds".

The options button

See here for a description of this button's menu items.

The most common mistakes when using serial connections

These are the most common causes for problems with serial communication:

Wrong baud rate selected

Make sure that the baud rate in your sketch is the same as selected in the Serial Monitor of Visual Micro. If both do not match, you won't be able to read and write characters to and from the serial connection.

Serial.begin() missing

You cannot perform any serial reading or writing operation unless you call Serial.begin() in your sketch. Usually, Serial.begin() is put into the setup() function of your sketch.

Wrong port on the Arduino board chosen

With boards that have multiple serial ports, like the Arduino Due, you must make sure that you work with the correct port in your sketch and that you have connected this port to your PC.

Wrong serial port selected on PC

If you connect your board to different USB connectors of your PC or if you use a different board, the COM port number may change. In these cases you must adjust the COM port setting in the Visual Micro Arduino Communications toolbar.

What is a COM port?

The CPUs used in most boards have one or more built in serial communication devices called UARTS. They work according to the RS-232 standard. The USB hardware on the board converts these signals into similar USB signals. On the PC side, there is a driver that can send and receive such USB-RSR-232 signals and that mimics a RS-232 hardware interface in your PC, that's why these drivers are called "Virtual Com Port Drivers".

From a PC application's viewpoint, everything looks as if the UART of your board's CPU was directly connected to a serial hardware interface in your PC.

Traditionally, serial ports in PCs are called COM ports and numbered COM1, COM2 etc.

That's why you can use any software that is able to work with COM ports in order to read and write data to and from your board.