About 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 vMicro > 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 Icon Note

A good start for experimenting with Arduino's Serial functions is the ReadASCIIString example provided by the classic Arduino IDE.
(read this page about how to open examples)

Anatomy of the Serial Monitor window

Sending and receiving data

Serial Monitor (1)

In the Outbound Area 1 you can enter characters. As soon as you click on the Send Button 2 , the string is sent to your Arduino board and can be received by the board via a Serial.Read() function.

Strings received from your board are displayed in the Inbound Area 3 .

Settings and other functions

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

Serial Monitor (2)


1 Connection button
By activating/deactivating this box, you can establish or interrupt the connection to your board. When the connection is interrupted, then the serial port is free for other programs on your PC.
If you activate this box again, the connection will be restored. The behavior of your Arduino board depends on the DTR checkbox (see below).
2 DTR button
The DTR line of your board's UART is used to reset the board and restart the sketch. If this box is activated (highlighted), 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 boards that have a separate small processor for serial communications.
3 RTS button
If this box is checked, Visual Micro  can start/stop incoming data to avoid buffer overruns with high data rates/slow PCs, by controlling the COM port's Rts line.
4 "Auto-Scroll" button

If activated, the inbound window scrolls as data arrives.  You can also click into the inbound window to temporarily disable pause the display and disable scrolling. Move the cursor to the end of the window to restart display.

5 "Auto-Recon" button

If activated, Visual Micro attempts to reconnect automatically when hardware is plugged in and/or becomes available. Shows the connection state of the board in real-time by showing the "Connect" button's text in green or red: Connect Button Green / Connect Button Red. Some types of ports do not support this feature.
Only available in the Pro Version of Visual Micro.

6 "Auto-Clear" button
When this box is activated, the inbound area of the window will be cleared every time the port is reopened.
7 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.
8 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.
"Line Feed": a Line Feed character ('LF'=0x0a or '\n') is appended.
"Both CR & LF": both a CR and a 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 "Line Feed" setting will be the right one. If in doubt, use the "Both NL and CR" setting.
Line end characters are a convenient and common way of indicating your board the end of a transmission.
9 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.
If the baud rates of your board and Visual Micro don't match, you will see no incoming characters or garbage.
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 Menu Button 10  Serial Monitor Options Button

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

The "CStr" Button 11  Serial Monitor CStr button On

Note IconNote:

The CStr switch is only available to users of the Visual Micro Pro version.

This is an On/off toggle switch.

If switched on, then the Serial Monitor outbound text box supports escape sequences, similar to those used in C++ and C#,  and shows them as 2-character sequences, starting with a '\':

The supported escape sequences are:

\0 NUL character (value 0)
\a "Bell" character (value 07)
\b Backspace character (value 08)
\t Tab character  (value 09)
\n Newline character (value 10 dec, 0x0a hex)
\n "Vertical tab" character (value 11 dec, 0x0b hex)
\n "Form feed" character (value 12 dec, 0x0c hex)
\r Carriage return character (value 13 dec, 0x0d hex)
\\ Backslash character '\'
A single, one byte character with the hexadecimal value of 0xnn
It is recommended to use the \x00nn variant of this notation, to avoid that characters following the sequence are traeted as being part of the hex code, like in "\x4fa", which would not result in '\x4f', followed by an 'a', but as an illegal character of value 0x4fa,  which will be converted to a '?' by Visual Micro.
Identical to \xnn


The \x..., \u... and \U... only support the ASCII character value range from 0x0 through 0x7f.

Note IconNote:

If you are working with such special characters, and you send them to devices like an LCD display: Please keep in mind that it depends on the device, if and how these characters are interpreted. E.g. typical 2- or 4-line LCD displays do not understand \n as a new line character. In this example, it is up to your sketch to send the right commands to the LDC controller, in order to advance to the next line.
This is also true for Non-ASCII-characters above 0x80, where devices may have their very own character sets.

The Log Button 12    Serial Monitor Log Button Enabled   /   Serial Monitor Log Button Disabled

The Serial Window writes sent and received data to a log file.

When you click on the button itself, you can switch logging on: Serial Monitor Log Button Enabled and off: Serial Monitor Log Button Disabled.

if you click on the submenu arrow on the button's right side, the Log submenu appears, where you can specify in which folder log files shall be written (2), and you can open this folder for opening and reviewing log files (1).

Serial Monitor Log Menu 

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, the opposite takes place: a driver receives the USB signals, and mimics a RS-232 hardware interface in your PC, that's why these drivers are called "Virtual Com Port Drivers", because they are no read serial ports, but they simulate them.

From a PC application's perspective, everything looks as if the UART of your board's CPU was directly connected to a RS-232 connector in your PC.

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

As a consequence, you can use any software that is able to communicate via COM ports for communication with your board, not just Visual Micro or the Arduino IDE.