Debug Arduino - Different USB Serial Port or SoftwareSerial?

by Visual Micro 26. April 2013 14:01

The project properties has an optional override of the serial port used for debug. LocalPort/RemotePort. For example LocalPort=COM10 and RemotePort=Serial2. Leave empty for the default which uses the standard Arduino usb/serial connection used for upload.

The local port relates to the pc and the remote port relates to the port the arduino will use for serial debug. Please note that some arduino boards have a single hardware Serial port, such as the Arduino Uno. Others such as the Leonardo have Serial, Serial1 and some such as the mega2560 have Serial,Serial1-4. For advanced users, LocalPort can also contain the name of a valid pre instantiated (prior to setup()) "compatible" object.

It is also possible to override the port speeds (LocalSpeed/RemoteSpeed). Normally the Remote and Local speeds will be the same unless remote devices such as xbee modules are being used.

If hardware serial port(s) are unavailble or if you prefer to debug using software serial then select “SoftwareSerial” from the RemoteTransport property.

Software serial defaults rx/tx to pins 7 and 8 but you can use the RemoteRX and RemoteTX project property to change to something else. (tip: In this case leave RemotePort empty)

It is recommended that speeds of 57k (recommended) or 19k are specified when using SoftwareSerial (especially if altering variables on a running microprocessor)

When using SoftwareSerial, leave the RemotePort property empty unless you already have a custom SoftwareSerial object in your code that you want the debugger to use (not recommended or tested).

You do not need to add the Arduino SoftwareSerial library to your project to debug using SoftwareSerial.

If you change the local port to a fixed value then that port will always be opened as a debugger after clicking F5 (or menu "Debug>Start Debugging").

If you want to use, for example, Serial2 for debug instead of the main serial port for debug then enter "Serial2" (without quotes) into the "Remote Port" property.

As stated earlier, SoftwareSerial allows you to define the pins to use for TX and RX. FastSerial works the same as HardwareSerial. To use FastSerial you must already have a project that initialises it then you can use the "Remote Port" property to define the name of the serial object. If "Remote Port" is empty then the "Serial" object is used by default

note: any property can be empty for defaults to apply

apm: If you are using the hardware serial ports of arducopter or arduplane then use the“FastSerial” option. 

How to connect arduino pins to the computer using rx and tx pins (or serial1,serial2, etc)

There are lots of different cables and usb/serial converts.

FTDI 5v Cable (there is also a 3v version)


(you might find it cheaper or a better alternative elsewhere)

Use the schematic to detrmine which two pins (rx and tx) to connect.

Rember to cross the rx/tx between pc and Arduino (rx>tx and tx>rx)


Modify Arduino Variables During a Debug Session

by Visual Micro 24. October 2012 14:57

Update Arduino MCU Variables During A Debug Session


There are three modes a breakpoint can work:

  • Disabled
    In this mode, breakpoints have no effect at all, but you can leave them in your sketch, if you want to.
  • Enabled, not halting execution
    In this mode, the breakpoint updates expression windows, trace and code windows but execution of your sketch continues without interruption.
  • Enabled, halting execution
    In this mode, when a breakpoint is hit, it halts execution of your sketch until you press [F9].

To disable Debugging/Breakpoints completely...

To enable Breakpoints...

To make breakpoints halt sketch execution when passed...

To let breakpoints continue execution of your sketch when passed...


Note 1: These settings become effective after a recompile/upload of your sketch
Note 2: These settings become effective immediately in your debugging session
Note A: These settings are global for all Visual Micro projects
Note B: These settings are project and configuration specific and apply to all breakpoints in the project
Note C: These settings are breakpoint specific



If you chose Break/Pause = True and your sketch is halted in a breakpoint, see the link below in the "See also" section to find out how to stop the sketch at that point, recompile and upload.

Related Topics

Miscellaneous Topics

Tip: Use =? to change the value of an Arduino variable


The debugger supports two different modes that allow variables to be updated. It is important to understand the difference between the two modes:-

Mode 1) Debug with "Enable Break/Pause=False" - Arduino does not stop

In this mode we can alter any of the assigned writable variables at any time however the change in value will only be recognised when the BreaPoint/TracePoint is hit/passed. The order that variables are updated corresponds to the order that you update them. For example if you update var1 which is in a breakpoint hit every 10 minutes then no other updates will be applied to any other variables until the 10 minutes has been reached.

If you are updating variables in a fast loop() then, subject to your code, the updates should also be applied immediately.

Mode 2) Debug with "Enable Break/Pause=True" and "WhenHit Continue Execution = False" - Arduino stops and waits for F5/Continue

In this mode only the variables of the current breakpoint can be changed.

With the mouse, select and hover over a breakpoint in the expression window to see information about the breakpoint

In the image below the breakpoint configuration specifies variables 'i' and 'a' to be read/write and 'c' is read-only. This configuration is specified using the "WhenHit" property of the breakpoint. 

Update Arduino MCU Variables During A Debug Session


Arduino Debugger Extensibility Performance Considerations

by Visual Micro 7. August 2012 14:00

Aug 2012: First draft - The Visual Micro Extension Framework

Visualizations provide a simple way to build powerful fully featured graphical plugins. It is possible to code both efficient and inefficient visualizations, the latter should be void!

Unfortuately all this power and flexiblity means that it is possible to create unwieldy and slow plugins that consume fast amounts of cpu power. This document provides a place to develop useful tips and suggestions that will help ensure the debugger continues to run at an efficient speed.

The Visual Micro interface provides a number of standard events that should be used to perform a little work as possible. For example in the OnDebugInit event is called once each time a debug session starts. The event should be used to initialise as much as possibly ensuring that a timer is used when possibly to prevent blocking.

The OnDebugExpressionsChanged event is called every time a breakpoint is hit. It is a high volume message and should be used to perform as little work as possible. Off-loading heavy processing to a regulated timer using a flag is highly recommended.

This OnDebugExpressionsChanged event also procides access to the dynamic xml properties from the MicroExtensions.xml config file. Looking up xml poperties is relatively heavy on cpu load as opposed to using class variables to store property settings. For this reason it is recommended that the OnDebugExpressionsChanged event is used to copy regularly used xml config properties into class variables. This will enable functions that are called regularly during a debug session to refer to the class properties and NOT the xml config properties.

When developing .NET visualizations (UserControls and Forms) testing using the slowest possible pc is highly recommended. A good target to aim for seems to be no more than a 3% increase in cpu load on a 1.8Ghz intel processor.

You can easily test the load your extension causes by adding a "Pause" checkbox to your control or form. Stop responding to the OnDebugExpressionValuesChanged event when the checkbox is true. Start a debug session and add a breakpoint that your visualization is watching for intoto the loop().  This causes a huge amount of debug messages to be sent to the pc. Clikcing the Pause checkbox should clearly show in windows task manager the additional cpu load.

The Visual Micro Extensibility Framework

by Visual Micro 7. August 2012 11:57

Aug 2012: First draft, - About The Visual Micro Extension Framework

Debugger visualizations are controls and/or windows written in any .NET language that enable us to graphically display remote debug data from a micro-controller such as an arduino. This means that any open source .net instrument/control project that can be found on the internet can be used as a visualization. The micro extension framework is a set of easy to implement inheritable classes that enable an application to interact with the arduino debugger and also with visual studio. Visualizations are loaded with full trust and have access to a computer in the same way that other visual studio addins can access a computer.

The Visual Micro inheritance system is optional, but provides an easy way to manage a debug state server. Below is an example of a >NET form constructor requesting notification of 3 visual micro debugger events. (OnDebugInit, OnDebugStateChanged, OnDataExpressionValuesChanged)

public SketchDebuggerExample1Window()
InitializeComponent(); //standard vs component init


  • this.OnDebugInit += onDebugInit; //fires when debug is started before connect to micro
  • this.OnDebugStateChanged += onDebugStateChanged; //fires whenever a debug state change occurrs
  • this.OnDataExpressionValuesChanged += onExpressionValuesChanged; //fires when a watched expression breakpoint is hit



Event sigantures

  • void onDebugInit(object sender, DebugInitEventArgs e)
  • void onExpressionValuesChanged(object sender, ExpressionValuesChangedArgs e)
  • void onDebugStateChanged(object sender, DebugStateChangedArgs e)

The Visual Micro debug upgrade is supplied with a few basic working examples such as Digital Pin Viewer, Analog Graphs and other examples, found on the internet and adapted to be intelligent visualizations. All of the example are supplied with full source, attributed to the original authors, and may be feely copied or extended.

Visualizations are therefore simply just .NET dll(s) and all that is needed to register them into Visual Micro is a MicroExtension.xml file. The xml file provides a unique name for the visualization, a caption, path to the dll and namespace.className of the control to be loaded. The file also allows "Watched" expressions "of interest" to be registered and setting of the "Startup" type.


"StartUp" types include:-

  • open when watched expression is hit
  • open when debug starts
  • open when user demands

The captions of all open/running Visualizations will appear on the "Running Visualizations" menu of the debug button in the serial tool window. This menu item allows us to hide/show active visualizations for the current project. (Settings are retained after vs closes)

The captions of any "When User Demands" visualizations will appear on the "Other Windows" menu of the the debug button in the serial tool window. This menu allows us to enable/disable a visualization for the current project. (settings are retained after vs closes)

Visualizations can be placed in specific folders in any one of three locations. Under the vm program folder, under My Document, under a sketch folder. The latter being specific visualizations for a single sketch project.

To create a visualization we create a normal .net class project and set the COM Visible property to true (Project>Properties>Build>Assembly>Com Visible checkbox. Adding a UserControl or Form to the class project and inheriting MicroDebugDataVisualizationWindowBase or MicroDebugDataVisualizationControlBase

To gain access to these inheritable classes the project must contain a reference to Visual.Micro.Debugger.Data.Extensions" assembly that is available in the global assemblies list. Tip: Right click the project and select "Add Reference". Alternatively copy and rename one of the provided Visual Micro examples which will already be configured with the reference :)

  • using Visual.Micro.Debugger.Extensions
  • using Visual.Micro.Xml

The xml object is an optional helper, if you have experience with xml you might have a better solution.

If you copy an existing Visualization we must replace the projects "Assembly" guid with a new one. Create a new guid using Tools>Create Guid. Set the new guid against the project by right clicking the project and clicking the Advaned or Assembly button

Click to enlarge. Soon to be released open source debugger visualizations. Digital and analog visualizations are included with the debugger upgrade. Build visualizations using ANY data from an Arduino

How can we debug our visualizations

Currently, the controls shipped with visual micro are .NET3.5 format so that they work for both VS 2008 and 2010 users. If you are using VS2010 and want to debug a visualization it is recommended that you switch the .NET version (project properties) to 4.0. If you do not do this then you will not be able to use "Start>debugging" in your c# or vb projects. Instead you will have to use "Tools>Attach to process" once you have an Arduino sketch open in Visual Studio. "Start>debugging" is the recommended debug option because it will allow you to edit/change your code during an active debug session.

It gets a bit confusing because to debug your visualization you will have two debug sessions running in two different visual studio instances. One for your visualization and one for the arduino :) You should also bear in mind that if you havd a sloe machine or if you hit a breakpoint in your C#/Vb code the pc will fall behind realtime with the arduino. This is not a probleme except it might cause confusion. So after breaking into a visualization and fixing a bug, I suggest re-starting the debug session.

When you try to start>debug a class project in visual studio you may encounter a message telling you that class projects can't be debugged directly. Our extension is a Visual Studio plugin so we actually want to debug visual studio when it is running our extension.

To make the debug work correctly, right click the project and open the project properties window. Click the "Debug" tab and click the radio button called "Start external program:". Enter the full path to your visual studio program in the box. An example being "C:\Program Files (x86)\Microsoft Visual Studio 10.0\Common7\IDE\devenv.exe". On the same screen, set the "Working directory:" to the folder containing the devenv.exe, an example might be "C:\Program Files (x86)\Microsoft Visual Studio 10.0\Common7\IDE\"

Once you have set .NET4 and configured the options above you can switch the visualization project to "Debug" mode and press F5. This will start visual studio so you can open a sketch project that will use the visualization. Configure the sketch for "Full" debug and press F5 to start the arduino debugger. When the visualization opens in the arduino debugger your breakpoints should be hit in the visualization control debugger.

Important Point: When a visualization has been loaded into a tool window by an instance of visual studio, the visualization (dll) will not be unloaded/released until the Visual Studio instance exists. A hidden visual studio tool window is still open and available. You will not be able to re-compile the visualization while the assembly remains loaded into another visual studio instance

Configuration Settings

Whilst a visualization dll can not be re-loaded without re-starting visual studio it is possible to alter the settings in the MicroExtension.xml which is re-loaded each time the debugger starts. This also means that is is possible to add new extensions without re-starting visual studio, Visual Micro will auto detect new xml files each time the debugger starts.

The MicroExtension.xml file also provides the facility for "User Settings" allowing the visualization to dynamically render different graphics based upon xml properties. This means that a single visualization control can be highly customizable without the need to re-compile or re-build the visualization dll.

Below is an example of a very basic visualization. The project provides 3 cicular dial instrument controls (like speedometers). When the arduino debug starts the visualization is notified and is also provided with the xml object of the MicroExtension.xml along with simple functions to provide the xml data to the c#/vb code.

The c#/vb visualization example responds to the visual micro "OnDebugInit" event and initializes its graphical controls based upon the xml properties. This means that you can create a flexible visualization control that can be used in different ways by different people or in different projects.

In the xml example below the xml is a know visual micro structure except for "ConfigSettings". This section(s) is entirely user defined but it is hoped we find and agree a standard that we can all work with.

The ConfigSettings section can be accessed in c#/vb as follows:-

  • XmlNode ConfigSettingSensor1;
  • ConfigSettingSensor1 = MicroGetVisualizationConfigSetting("Sensor1");
  • ValueExpressionNameSensor1 = XmlHelper.GetAttribute(ConfigSettingSensor1, "ValueExpressionName")

MicroExtension.Xml example follows

<MicroDebugExtension Startup="WhenHit"
Caption="Sketch Debug Example 1"

  <Visualization Type="ToolWindow" 
<Expression Name="ValueOfDial1">analogReadingA</Expression>
<Expression Name="ValueOfDial2">analogReadingB</Expression>

<ConfigSettings Name="Standard">
<ConfigSetting Name="Page"
        <ConfigSetting Name="Sensor1"
DialText="Something 1"
        <ConfigSetting Name="Sensor2"
DialText="Something 2"
<ConfigSetting Name="Sensor3"
DialText="Something 3"



Arduino Debug Release Information - Breakpoints Example

by Visual Micro 19. May 2012 13:59

The Arduino debugger upgrade for Visual Studio is due for release in June 2012. The date has slipped slightly due to high work loads. The debugger includes eveything required to set conditional breakpoints, trace messages, expression reporting step through pre-defined debug points. The Arduino debug tool does not require you to make any code modifications to your arduino source code so it is fully automated.

In the Arduino breakpoints below we see 5 breakpoints of various types. Two breakpoints have conditional expressions, one breakpoint produces a trace message and also reports the value of variable i. An unlimited number of Arduino variables to watch can be set per breakpoint, the message is also optional. Two breakpoints have hit conditions (n times before each hit)

Read more about the Arduino Debug Tool

Please EMAIL beta @ if you would like to be a beta tester

Configure Arduino Debugging to use Software Serial

by Visual Micro 6. May 2012 12:00

The method of "Transport" used to send or receive debug messages on the Arduino defaults to standard serial ports such as Serial or Serial1 etc. The default (empty) is "Serial" however the RemotePort project property can be altered to another port suppoted by the micro-controller.

The "RemoteTransport" project property allows SoftwareSerial and spare digital pin(s) to be used as an alternative to the built-in Serial ports. The SoftwareSerial library is automatically included duiring debug compilation if required. The RemoteTx (and RemoteRx for Debug Break/Pause/Step) project properties should be populated with the digital pin numbers used for tx/rx on the Arduino. See the software serial guide when choosing digital pins

To use FastSerial the project must include all required library references and the RemoteTransport project property must be set to FastSerial. Other methods of debugger "transport" can be added by advanced users. We hope that in the future debugger transport will be configurable using a simple user interface. Please ask in the forum for more information.

All of the options shown below are default except for the FastSerial setting. 

click the image for a draft debugger overview tutorial


  • To use a different Arduino serial port such as Serial2, enter Serial2 as the "RemotePort" property
  • To use a different PC serial port such as COM7, enter COM7 as the "LocalPort" property
  • To switch from the default speed of 115200, set the "LocalSpeed" to value from the pick list, RemoteSpeed will change automatically to match.
  • Apm users should not that the "Throttle" properties relate to debugger bandwidth throttling and are nothing to do with drones :) Leave the throttle at the defaults, learn more about the throttle via the forum.
  • If using SoftwareSerial on spare digital pins you should clear the RemotePort property and set the Remote Rx Tx Pins to the digital pins that are connected to the serial device or cable. If "Break/Pause" and "Startup Wait" are not enabled (default) then only the Arduino Tx pin is required

And a few hints that might mean something at some stage...

1) Validation Skip (project property) 

Set to False if you are not altering the arduino code in a way that might cause compilation errors. This will skip the "release" build of apm that happens prior to the debug build. (Saves time)

2) TracePoint Throttle (project property)

An unconditional breakpoint/tracepoint example in the 50hz loop is a good example for us to use...

By default, for newer users and non fastserial users the breakpoints are throttled so that the 50hz loop will only run at about 8-12hz. Visual micro ensures an 80 millisecond delay between breakpoints. 

FastSerial, if available, is more efficient than normal Arduino Serial therefore you could change the project property called Throttle (ms) to, for example, 30 (milllis) which would improve the speed. Leaving the Throttle (ms) empty uses the default of 80ms.

or b)
Try setting "Throttle Enabled = False" to entirely disable throttling in which case apm will send as fast as it can but it is possible for the arduino buffer to overflow causing the debug to stop working or invalid serial packets to be received by the debugger

or c)
Set the breakpoint "HitCount" to 50. Because we are in the 50hz loop this should produce one debug breakpoint message every second allowing apm to function at full speed inbetween each breakpoint message

or d)
Set the "Hit Counter" project property to milliseconds and all the breakpoint "HitCounters" will no longer be treated as counts, instead the HitCounts will represent milliseconds. So a breakpoint "HitCount" of 1000 would produce a debug  message exactly once every second regardless of where you put the breakpoint.


When sharing the serial port with the arduino code you might expect to see some "junk" in the serial window. This is normal, the debugger windows will workaround the "junk" and function correctly. If your arduino program reads the serial port then you will not be able to switch on the break/pause facility in which case you should use a different arduino serial port or SoftwareSerial on two digital pins.

The throttle setting is very dependant on the speed of your pc. If the arduino sends messages faster than your pc can process them the pc display will fall behind the arduino. The pc display will no longer be real-time and will be confusing.

Reminder: Please read our disclaimers !!

Break Points Can Be Disabled But ...

by Visual Micro 5. May 2012 18:46

You will notice that in Visual Studio breakpoints can be disabled. Visual Micro always sends all breakpoints to the Arduino during compilation but will stop reporting disabled breakpoints.

This means you can switch on/off breakpoints during a single debug session by enabling or disabling them.

If using debug break/pause with disabled breakpoints the breakpoint will still be active in the arduino but the pc will automatically send an F5. This means that disabled breakpoints will still cause the Arduino to work more slowly than normal but that the breakpoint will not require users to manually press F5. This feature might be useful in some situations or to freeze the variables window for certain variables.

It is recommended that breakpoints are exported and/or deleted when not being used.

BreakPoint Hit Count Condition

by Visual Micro 5. May 2012 18:36

Instead of, or in combination with a conditonal breakpoint expression (as described in earlier posts) to make an Arduino trace or break point we can use the "Hit Count" dialog.

The hit count dialog is opened by right clicking any break break and selecting "Hit Count" from the menu that appears (described in detail in earlier posts). The Hit Count dialog allows us to select 4 options.

The example below is self explanatory. If we are adding a break point into a frequent arduino loop we might set a hit count of 30000. In effect this will increment a counter in the code until 3000 is reached, then the breakpoint will be executed prior to the counter being reset to 0. To use a normal "count" for a hit counter then set the project or global property "Hit Count" to "Counter". The default "Hit Count" is "milliseconds"

Tip: The hit count is automatically combined with any conditional expression (as described in earlier posts). Example, we use "break when hit count is a multiple of 250 and we set the HitCount in the project properties to milliseconds (is the default) then we will see a breakpoint or tracepoint 4 times per second (every 250 ms)

How to control the Arduino execution speed during a debug session


note: when using non-breaking tracepoints the stream of debug messages are processed on the pc in batches of up to 10 per second (also depends on the amount of data). The time displayed in the pc debug trace is the time each message is processed on the pc, not the time the message was sent from the micro-controller. For example, we might use a tracepoint at 4hz (every 250ms). In this case the debug data will be an accurate reflection of the micro_controller every 4hz however the millisecond values in the pc trace might not appear enitrely consitent. 

Break/Pause Into Source Code

by Visual Micro 5. May 2012 17:59

2015 - The following is old documentation. In many ways it does still apply but the debug features are better described in our Documentation section

The example below shows both automated and manual arduino source debugging features. The "old style" manual debug of arduino is shown in the code. Some of the automated features are shown in the "When Breakpoint hit" dialog

Individual points in your Arduino source code can be configured to break/pause or simply trace/continue without pause. The configuration settings change depending on the type of break or trace point. When a break/pause is hit Visual Studio will automatically open and select the line of arduino source that contains the current break point.

Most points can be configured to either continue or break/pause using the breakpoint message window as shown below.

Untick the "Continue Execution" checkbox to force a pause. Behind the dialog in the example we can see that the Arduino is paused on a breakpoint. Pressing F5, clicking any of the Visual Studio "Start>debug" commands or sending any serial data will re-start the Arduino program.

This example shows a few of the options that allow Arduino source code debugging

IMPORTANT WARNINGS! It is only right that we make the following statements very clearly...

Before enabling Arduino debug "break/pause" you must carefully consider what will happen if the Arduino suddenly stops on a breakpoint. Will your flying machine drop out of the sky and injure someone or be damaged. Will a robot crash? Will a motor be stuck on full power? Will a device stop responding and cause a critical problem? This is entirely your responsibility, if you are in any doubt then ask questions on the forum but please do not use this feature until there is no doubt! The same applies to the ability for the Arduino to pause at startup.

All arduino debug pause features provided in Visual Studio can not be relied upon in sensitive or dangerous siutations. This is because of the use of the serial port for the debug "continue" command. In the current version any data transmitted over the debug serial port will cause the Arduino to continue program execution which might be unexpected in many cases such as electrical interference and stray serial data.

Debug break/pause should only be used with breakpoints that will be hit every so often otherwise you will spend your time hitting F5 (continue) lots and lots of times :) If you mistakenly set a break condition that happens to often you will find that you can untick the "connect" checkbox on the serial window to stop the serial comms. This will, ineffect, stop the debug session but bear in mind that the Arduino will still be in debug mode.

Because the Arduino can be in debug mode and might be paused while Visual Studio is not in debug mode it is suggested that you either upload a "release" version when you finish debugging. This will ensure the Arduino is always in a known state. 

It is strongly recommended that you switch on the DTR setting on the serial window or in the Visual Micro options. The DTR setting will ensure that the Arduino is reset whenever  the serial window connects and/or debugging starts. Without the DTR setting it possible to start debuging when the Arduino is already paused on a beakpoint which will be confusing for most users.

Debug Break/Pause is enabled by selecting the project in the Solution Exporer and viewing the properties window (not right mouse click properties, the Property Window). Set Enable Break/Pause to True. Each time Break/Pause is enabled for a project a warning is displayed.


Optionally make use of the _DEBUG symbol in your Arduino code

by Visual Micro 5. May 2012 17:36

Nov 2012 - This document is out of date. A new prject property called Define _DEBUG allows you to enable this property in the standard plugin. The #define will be called _DEBUG

When debuging is enabled the _VMDEBUG symbol allows code to be used "instead of" or "in combination with" the Visual Studio debug tools

The example below shows the wrong name for this symbol


Optional Message Viewers

by Visual Micro 5. May 2012 16:47

Visual Studio provides a number of text message views during a arduino debug session. Configuration of which windows are used to view messages is available using the debug options sub menu on the active debugger Serial window as shown below.

Messages can be directed to any combination of 3 windows:-

  • Serial Viewer
  • Message Viewer
  • Trace Viewer

The example above would allow messages to be appear in a dedicated message window (as shown below) and also in the trace window (as shown in previous posts).

Below shows a "message only" window which is free of trace messages

Below shows a "trace only" window which is free of messages. The example below was created by unticking the "Trace" sub menu shown at the start of this post.

Running Variables and Expressions Viewer

by Visual Micro 5. May 2012 16:40

In addition to showing hit data the "Variables and Expressions Window" provides a number of additional columns that are enabled by right clicking the list (as shown below)

As with all Visual Micro windows, the Arduino Debugger Variables Window can be docked. The window positions are retained on a "port by port" basis and scrolling locks the variables/expression name column to provide clearer analysis

During Arduino program debug, variables and expressions are automatically displayed inside a grid grouped by breakpoint location. Double clicking a variable of breakpoint will jump to the respective line of source code

Source Code Modification Tracking

by Visual Micro 5. May 2012 16:24

A debug session continues on the Arduino until a release program/sketch version is upload therefore it is possible for the source code to be different from the source code running on the Arduino. For this reason breakpoint configuration and source code is saved during compilation and used to display messages and variable data during debug.

Tip: Hovering over the name of a breakpoint provides a summary of the code that was uploaded to the Arduino. In the example below we see that the Arduino is using a random number between 0 and 2000 when the code has been altered to between 0 and 4000


Conditonal Breakpoints and Tracepoints

by Visual Micro 5. May 2012 15:25

If we need to debug fast running arduino code we might only want to trace exceptions or conditions within a certain range. Visual Micro allows any expression to be used as an arduino breakpoint condition.

To add a debug conditon to an arduino breakpoint we can use the right menu menu to select the breakpoint options menu. it is also possible to set a "Hit Count" allowing a tracepoint to be reported every x times that it is executed (hit) by the arduino cpu.

The example below shows an arduino debugger tracepoint that reports when a random number of between 0 and 2000 has a value between 1000 and 1500. The debugger tracepoint reports the value of i and also the value of the Arduino millis() (milliseconds since startup). "Is True" or "Has Changed" may be used to distinguish between the type of condition that is required. In each case the expression entered must either return boolean true/false or a value. The example below uses the "Is True" condition to ensure the value of i is within the given range.


The image below shows this conditional tracepoint when an arduino is running in debug mode. Notice the variables viewer displays both variable and expression along with min and max values. In the example below the min and max values of the condition have already been reached. 

Items in red show data that has changed since the last point was hit.

Trace Messages and Variables/Expressions

by Visual Micro 5. May 2012 14:30

Right mouse clicking a debugger break point in the source code or in the debugger Breakpoints Window (CTR+ALT+B) provides a number of menu items relevent to the breakpoint.


Clicking the debug "When Hit" option opens the following dialog window allowing us to optionally print a message that includes variable data or we can just report variables to the debug tool. Debugger messages can be as long as is needed because they are not compiled into the Arduino program. Messages are stored locally on the pc and displayed when a break or trace point is hit.

The example below shows how to create a dynamic trace message that includes variable data. Note that requests for variable data are enclosed in {brackets}. Any expression that returns a numeric (int, float etc) value is allowed and any number of expressions can be included in the message. The "Run Macro" option will be supported in future versions of Visual Micro. The "Continue Execution" feature is only relevent if "Debug Break/Pause" is enabled.

After making changes to arduino debugger breakpoints or source code the project must be compiled and uploaded. The easiest way is to press F5


If the debug message soley consists of expressions (no text) then a trace message entry is not displayed. The variable/expression inspector shown below will automatically open when a debug session starts.

Double click arduino debugger variables and/or trace message to jump to the respective source code line.


Basic Trace Point

by Visual Micro 5. May 2012 14:11

When debuging has been enabled for a configuration a debug session can be started by pressing F5, clicking menu item "Debug>Start With Debugging" or the standard "Start Debugging" icon on the Visual Studio tool bar.

The first thing to note is that two compilations are performed. The first is normal compilation of the sketch to ensure it is free of errors then the second to include debug information. Below you can see the difference in memory between a release and debug build. The difference would be smaller if our test sketch already referenced the serial port and other basic arduino properties. Therefore this example probably represents a worst case senario.

If the serial port monitor was already open prior to upload then Visual Studio automatically displays the debug trace window. Otherwise the serial port monitor should be opened for the trace window to be displayed. The example below shows a running tracepoint. In a real world project we might have multiple break or trace points. Double clicking the trace point will jump to the correct line in the source code.

Creating a Simple Arduino Debug Tracepoint

by Visual Micro 5. May 2012 09:09

In this example we create a simple debug trace point using the main Arduino serial port and the default Visual Micro settings. This article assumes that arduino debugging in Visual Studio has been enabled (see this post for a how to).

The Visual Studio Debugger Breakpoints Window is opened using CTRL+ALT+B or by clicking the menu item Debug>Windows>Breakpoints. Alternatively you can right mouse click the tool bars and show the "Debug" bar as shown below above the source code.

In the example below the breakpoints window is displayed below the source code. A single breakpoint has been added by clicking the left margin of the source.

During compilation - How are breakpoints added to a temporary copy of the code?

During compilation, breakpoints are added to the end of the selected code line, can not be added to comment lines but can be added to empty source lines. Adding breakpoints to empty source lines is recommended because it ensures you are happy with the exact position the debug code will be added to a copy of the code. For example, consider the following line of code:-

if (foo) {a=0;}

In the above example the debug engine would compile the following code which involves a significant code change and might, in a more complex example, lead to unexpected results. The debug engine tries a few tests to attempt a code injection and might fail or produce the wrong code. Hence the rule, add breakpoints to empty or simple lines of codes.

if (foo)
//some debug commands will be inserted here

SUGGESTION: Add debugger breakpoints to empty or simple lines of codes, see why at the end of this section

Settings Explained

by Visual Micro 5. May 2012 08:04

The debugger was released May 2013 as an upgrade to standard Arduino plugin. The plugin is free, the debugger has an rrp of $49 but is currently being offered for approx. $15, includes 2 years of support and updates. A 30 day free trial is available in all versions of Visual Micro

The project properties window is available when the project is selected in the Visual Studio solution explorer. Properties in the "Micro Debug" section are only used if (Micro Debug) is enabled (see the example below). The properties are the Arduino debugging options that are available.

IMPORTANT WARNING - Enable Break/Pause causes the Arduino to STOP/WAIT when a breakable point in the source code is reached. You must only enable this option if you understand the consequences of the Arduino stopping and waiting for an F5 (continue) command. Further more, because the debug uses the serial port to communicate any transmission to the arduino serial port will cause the arduino to continue. REMOVE all propellers and consider the dangers of debug pause prior to using this feature! For this reason the default for this option is false (off) which forces all break points to become tracepoints regardless of their settings.

Jump To Source is automatically enabled when a pausable breakpoint is hit. This option forces jumping to source for all tracepoints so must be used with consideration to how fast visual studio can react. For example if we only trace when a sensor button is clicked or when a condition happens infrequently (such as every 20 seconds or longer) then this option can provide a useful animated view of the code that is being executed.

Remote Port enabled us to override the serial port that the debugger uses. By default it uses the main Arduino Serial port and initialises the port speed to 115k. You may optional override the speed of the port or both the speed and the port. This option might be useful if you already use the main serial port or if you want to manually initialise the debug port in the sketch setup() function.

Startup Message provides the ability to send a startup message from the arduino when it is in debug mode

Startup Wait is used in cojuntion with Enable Break/Pause and automatically forces the arduino to wait for F5 (continue) when it starts or resets. The Startup message is displayed in the trace then the Arduino will pause

Tip: Press F4 or "View>Properties Window" if the debugging properties are not displayed. The visibility and position of the project properties will be remebered when you re-start Visual Studio

How To Enable Arduino Debugging

by Visual Micro 5. May 2012 07:05

This page is for users of Visual Studio 2010, 2012 and Atmel Studio 6.1. Please review our documentation index for more up to date full featured debugging.

Note: Since version 1404 (Apr 2014) simple debugging is enabled for all configurations (debug/release/custom) by default.

To enable finer control of the debugger un-tick "Tools>Visual Micro>Automatic Debugging". In this mode the debugger can be enable for a specific configuration such as the Debug configuration (see tool bar)... 

Open the project properties window by clicking on the project name in the solution explorer and either pressing F4 (ALT+ENTER in Atmel Studio) or by selecting the menu "View>Properties Window".

Set the project property called "(Micro Debug)" to "Full" to enable Arduino usb debugging

The default debugger settings use the built in Arduino "Serial" port at 115200 and the projects local upload port/usb

Click the grey left side border next to source code to add breakpoints. Right click breakpoints to set properties such as variables to watch

Per Configuration

"Per configuration" settings means that the settings are saved based upon the current Visual Studio configuration such as "Release" or "Debug".

In the following example the configuration is set to "Debug"

The following example is using the default arduino software serial library.

Tip: The TX/RX pins in this example are the default so did not need to be entered. The same applies to the speed settings at 115200. To use the defaults you can simply set the transport to SoftwareSerial


To enable debug you do NOT need to add or alter any of your Arduino source code. ANY arduino project can be debugged.

Bear in mind that if you don't configure at least one source trace/break point(s) then you won't see very much in the trace other than an Arduino startup confirmation message.

To avoid confusion it is recommened that debug is enabled when Visual Studio is set to the "Debug" configuration. This then allows the configuration option to be used to quickly switch between a Release or Debug Arduino build and upload.

IMPORTANT WARNING - Enable Break/Pause causes the Arduino to STOP/WAIT when a breakable point in the source code is reached. You must only enable this option if you understand the consequences of the Arduino stopping and waiting for an F5 (continue) command. Further more, because the debug uses the serial port to communicate any transmission to the arduino serial port will cause the arduino to continue. REMOVE all propellers and consider the dangers of debug pause prior to using this feature! For this reason the default for this option is false (off) which forces all break points to become tracepoints regardless of their settings.

Debug Arduino - Overview

by Visual Micro 5. May 2012 06:18

news: june 2018 - Visual Micro is now a single version with all features enabled.

this is old documentation, still applies but has been superceeded wth better docs! please click Documentation at the top of this site to learn about visual micro. Thanks!

Update Arduino MCU Variables During A Debug Session

above image is just an example, the code does not do anything useful!

Usb (serial) or network (Bridge/Console) debugging for Arduino improves productivity by allowing us to monitor the running Arduino code, variables and expressions.

Conditional or timed breakpoints can be used to trace or pause the Arduino code. The values of variables can be modified with or without pausing the Arduino micro-controller.

The debugging tool automatically combines the debug facilities of Visual Studio, a world class IDE, with simple Arduino usb/serial commands without altering any of your Arduino source code (also supports Teensy 3, Yun, Uno (all Arduino), Due, Galileo Energia, StellarPad ). 

Automatic debugging for novice users is enabled after first install. This ensures that the debugger always runs for the debug>start command and also adds an example breakpoint (if no breakpoint(s) has been created).

To switch the debugger to normal mode, as described in the documentation, untick "Tools>Visual Micro>Automatic Debugging"


More info & blurb

note: Click the image for more details. The message viewer in the image above was frozen at an informative position for the purposes of the example. Yes the code in the example is rubbish and doesn't do anything useful. It's just an example :)
The image above shows a running Arduino debug session in addition to the latest feature of allowing Arduino variables to be changed during debug. The arduino code (bad example) shown is the entire arduino program source. There is no need for serial.print() debug statements in our code.

Notice that in the image all of the variables have different values to the defined source code. This is because the variables have been modified using the "watch expressions" window without causing the Arduino to stop or recompile. The image also shows the message trace which is one of the 3 available trace windows provided by the debugger. Read about how to modify variables on an Arduino while it is running

The text messages assigned in breakpoints are not stored on the Arduino so they can be as long as is needed without concern of excessive Arduino memory usage. Whilst the debug version of an Arduino build will result in a large program size (depends on the program code) the huge savings of SRAM, caused by the removal of serial.print() debug messages from code, can immediately solve some erratic arduino program failures.

In the lower section of the image is the break point configuration list makes it possible to see how break point messages are constructed and that they can consist of a mix of text and/or expressions. Any valid Arduino variables and expressions can be used in breakpoints messages, watch expressions and/or conditions.

Variables and expressions in breakpoints are automatically made available in the expression watch window grouped by break point. Various views of the Arduino data are provided including bin, dec, hex in addition to summary values min/max. The Min/Max values are useful to the range of values encountered.

During an active debugger session, if the debugger is configured to share a serial port with the Arduino code, serial messages omiitted by code will continue be displayed correctly in the serial monitor(s).

Improves Productivity - Works over usb, xbee, bluetooth and more

Developing small and large Arduino projects often depends on scanning the web to find the ranges of values produced by various sensors such as giro, temperature, accellerometer etc. The debug tool provides this information and also shows min and max values for every watched expression which makes it easier to see how sensors are working.

The debug tool has a huge array of options, the default settings are configured for new users allowing little or zero Arduino knowledge prior to staring a debug session.

The debug tool requires only a USB connection to work and also supports SoftwareSerial (used if the main arduino usb is being used for other purposes). A great benefit of using a simple serial transport for debug data is that it wil also work over GPRS and Radio such as XBee.

Real-time trace and/or message display - entirely replace the need for serial.print() statements

Click to see full size image of Arduino programming in Microsoft Visual Studio 2010.

Conditional Breakpoints - Right click break point context menu

The image below shows the context menu that appears when right mouse clicking an Arduino break point in Visual Studio 2010

For the remainder of this document we will use the term "Break point" meaning break point or trace point.

Breakpoints are more effective when they are made conditional by the use of additional code such as if (x>100) or (HitCounter>10) or (TimeSinceLast>100ms) etc. Experienced pogramers will be used to this type of conditional exception reporting but in normal Arduino programming this means surrounding the textual debug messages with additional code. This means editing the Arduino program source every time the conditions or debug messages need to be modified. It's slow messy work which causes development to take much longer than it should.

Messages and Variable/Expression Watch - Replace those old arduino serial print() debug statements!

For non-arduino programs, Microsoft Visual Studio includes very easy to use and feature rich interfaces that enable programmers to set breakpoints, conditions, and many other settings. The ideal debug solution for Arduino would be to allow these standard debug features of Visual Studio to be used within an Arduino project. 

The debug facility from Visual Micro does just that. It enables programmers to configure debugging of an Arduino program in the same way a windows program can be debugged. The difference is that Visual Micro interprets the debug commands into Arduino source code dynamically when a programmer decides to upload a debug version of an Arduino program to an Arduino micro-controller. This happens in the background and well away from the real code leaving the original Arduino program in a clean and untouched state.

The image below demonstrates how to create an Arduino debug trace message combined with expressions in curly braces. The expression values will also be available in the expression watch debug window.

This example shows a few of the options that allow Arduino source code debugging

In theory, by injecting these additional commands into Arduino code we use additional memory that a normal running Arduino program does not use. However the Visual Micro debug tool does not compile string messages onto the Arduino, instead it retains the messages on the pc and displays them in the debug trace windows at the appropriate times. This results in smaller debug versions of Arduino programs than might normally be achieved with the "old style" Arduino debug facilities.

Feed back from users about the new debugger has been excellent so far. It seems to make Arduino development much easier for both new and experienced users. The result being faster production of working code and successful completion or all types of Arduino project in vastly reduced time-scales. Less hair loss and head scratching!

Watch the Values of Variables and Expressions

As standard the debug tool is able to track complex Arduino expression values with options to see Min,Max,Hex,Binary representation of all debug data.

The expression watch window provides a number of additional options covered in detail in the wiki.

Breakpoints in the expressions watch window also provide a tool tip showing useful configuration and original source code.

The image below shows some of the options available in the Arduino expression watch window.

Hit Counters

An alternative to conditional breakpoints or code conditions is to use the "Hit Count" facility of a break point. By default we can set the number of times a break point is reached before the break point is activated. Example: Activate a break point after 200 hits or every 200 hits etc.

In Arduino terms setting the number of hits might not be so useful because the number might be in the 10's or 100's of thousands. For this reason Visual Micro provides a project property called "Hit Frequency Type" that can be changed from "Count" to "Milliseconds". This change causes all hit counts of the current project to signify a timespan in milliseconds instead of a numeric count. The result in our example would be to activate a break point after or every 200 milliseconds.

Flexibility and Considerations

The open source visualizations are also created using Microsoft Visual Studio and C#. Any .NET (windows) language can be used to create additional debugger visualizations which are easily registered so that the debug tool knows about them. Visualizations can be global for all projects or local to a specific project, can open on demand or in response to certain expressions becoming available within a debug session.

The debugger is not a full hardware debugger, for example it is only possible to watch expression values of expressions that are registered when adding a break point. Break/pause allows only to step between breakpoints and not each line of source between two breakpoints. It is however much easier to use than a hardware debugger and more flexible in terms of data visualization and conditional reporting.

The tool should not be used in dangerous situations without being fully aware of how it works and what possible problems might occur. For example a break point that pauses when a drone rolls past a given angle would cause the drone to crash. Obviously!!

A single Arduino Debug session can run for years - We can re-connect to an existing debug session at any time

One other difference between normal windows application debug and the Arduino debugger is that the Arduino might be running for a significant time such as a month or year. As an example, this means that a debug condition on a remote weather sensor might not be hit for a year. In the meantime the original source code might have altered. Windows debugging does not cater for this situation but the Arduino debug does...

The image below shows how the debugger has retained knowledge of the code that is running on the Arduino, whilst the Visual Studio source code has been altered. You can see that the Arduino is producing a random number between 0 and 2000 whilst the code has been altered to produce a random number between 0 and 4000.

Sit Back And Watch Your Program Running

The debugger currently supports two modes. Continuous operation and/or ability to break/pause at certain points in an Arduino program. Both modes allow trace, messages and variables/expression watch. 

Break/pause mode allows stepping from break point to break point, unlike a hardware debugger that allows stepping through every code line. An example of break/pause might be a break point on a line or code that only executes when a button connected to an arduino is pressed (pushed). In this case, when the button is pressed Visual Studio will open the source code containing the button click (if not already open) and highlight the line of code that has been reached.

When demonstrating code to other users, or to see the code of an arduino program that is unfamiliar, well placed breakpoints can be used to clearly show the flow of an arduino program. This is achieved by switching off break/pause and switching on "Debug>Break point Manager>Jump To Trace points". ("Debug" is the little bug icon on the debugger serial window). With these settings applied, all breakpoints will not pause but the respective lines of source code will still be displayed and highlighted.

The result is the cursor will jump from code line to code line and/or source file to source file showing visually what arduino code is actually running at any moment in time. This feature is only useful with well spaced breakpoints that occur no more than a couple of times per second (depends on the speed of your computer)

Execution Speed

The default settings of the debugger are designed for new users and simple non-timing critical project debugging. This enables breakpoints to be used liberally in fast running loops although this is not recommended. We have to keep in mind that the pc can only effectively process 10 or 20 debug messages per second yet in theory the Arduino could send 1000's per second. The debugger will automatically prevent the arduino from swamping the pc should the possibility arise as a result of break point configuration/placement.

All debugger defaults can be overridden or disabled entirely by more expert users. However, if well placed conditional breakpoints are used, there should be no need.

Automated Analog, Digital and Memory Usage Visualizations

In addition to providing break point/step/trace the debugger has a range of other features, some of which cause additional debug messages to be automatically generated,  such as Analog Pins Graph and Digital Pin Visualization.

This automated visualization of Arduino Analog and Digital pins can be achieved in two ways. Either by enabling "Micro Reports" in the Project properties or by adding special break point "WhenHit" watch expressions such as {@ReportDigital} and/or {@ReportAnalog}. The break point facility allows finer control over when visualization reports are generated, the automated version are generated at the start of each Arduino loop().

It is recommended that automatic reports are only used if there are no frequently exciting non-pausing breakpoints and that manual break point reports are used, when required, at all other times.

Extensible - Build/customize open source visualizations and plugins for the debugger

In addition to the standard debug trace and expression viewers the debug tool provides graphical visualizations or Analog and Digital pin values along with free memory graphs. The visualizations provided by the debugger are open source, can be altered to represent any data that is being processed on an Arduino.

Click to enlarge. Soon to be released open source debugger visualizations. Digital and analog visualizations are included with the debugger upgrade

Arduino Debug Visual Studio 2010 The image below shows a running debug session in Visual Studio 2010 along with, break point expression watch, open source graphical visualizations of Analog and Digital Pins + Custom Guages

Click to enlarge. Soon to be released open source debugger visualizations. Digital and analog visualizations are included with the debugger upgrade. Build visualizations using ANY data from an Arduino

View all arduino debugging tutorials. Email beta [at] to obtain a free copy of the debug tool

How to try and buy + important notes

Visual Micro + and the usb debug tool is available on a 14 day (full) trial or for purchase at 19GBP ($29 approx.) single machine, 29GBP 3 machines plus there are various license options available for commercial use (includes 24 months of free upgrades). Educational establishments should contact us for free licenses. 

This is not a perfect technical solution due to the principals of using the arduino core for debug purposes. The debugger can only debug code where an arduino serial command could possibly be placed. (.pde and the cpp/c files of an arduino sketch). In cpp files, only static c++ classes may be debugged.

This integrated software debugger is not the same as a full hardware debugger. It can not be relied upon for use with sensitive and dangerous projects. However it is an easier to use "real world" alternative and contains more productivity features. Requires at least one usb connection and an Arduino


With the default settings the debugger uses the main arduino upload serial/usb port for debug. If you are new to Arduino and have technical skills you might experiment with "timer0". Timer0 is used by the Arduino serial/usb port so this will prevent the debug from working correctly. In this case use timer2 or switch the debugger "RemoteTransport" to softwareSerial. To use SoftwareSerial you will need a serial/usb converter or an FTDI cable.

References and Disclaimer

The standard plugin for Visual Studio was released in 2009 and has been updated constantly during since. The plugin provides 100% compatible programming and upload to any Arduino hardware. The plugin is used by thousands of people around the world.

New users should note that any type of debugging with a micro-controller can affect the speed at which the cpu (or connected hardware) operate and should not be used, or should be used carefully, for timer critical applications. This said, there are few applications that are timer critical so in the main, debugging is widely used.

This product is provided without warranty and is used entirely at your own risk. The same applies to the Arduino programs that this plugin and debug tool produce. No liability is implied or accepted for anything!

please read the disclaimer and the terms of sale, at least 2 years of new version updates and support on a best endeavors basis, if your circumstances prevent you from buying the debugger please contact us, requests will be dealt with on a case by case basis and a response will be given as quickly as possible but might take a week or longer. The debugger will work better with some hardware than others. Please use the trial and be sure this product meets your needs before buying it. Thank you.