Visualizing Global Variables while Target is Running with Eclipse and MCUXpresso IDE

By default, Eclipse provides ‘stop-mode-debugging’: in order to inspect the target code and data, I have to stop the target. But with the right extensions as present in the Eclipse based MCUXpresso IDE, it is possible to inspect the target even while it is running.

Graphing Variables

Graphing Variables

Inspecting and visualizing variables with the debugger while the target is running is incredible useful: I don’t have to stop the target to inspect the state of the system. But of course there are limiations: The debug probe only can read memory mapped variables (so no CPU core registers), and the variables should be global (it does not make much sense to use local variables, as their location on the stack changes all the time). The amount of data (number of variables, frequency of updates) is limited, so this works for a few variables updated every few 100s of milliseconds. The feature is usually named ‘live variables’ or similar.

I’m using the NXP MCUXpresso IDE V11.0 which implements the ability to read and interact with the target while it is running (gdb non-stop mode). That features has been introduced from V11.2 and has been enhanced in later releases with V11 the most recent one.

The feature depends to some extend on the debug probe capabilities, and with V11 it works seamless for all supported probes, including P&E, SEGGER and the NXP LPC-Link2/CMSIS-DAP ones.

If using LinkServer as debug connection, make sure it is is in Non-Stop mode. If it is in full-stop mode, see how to change an existing configuration.

LinkServer Non-Stop Mode

LinkServer Non-Stop Mode

To monitor the variables, the ‘Global Variables’ view is used:

Global Variables View

Use the ‘glasses’ icon to open a dialog to select the variable(s) to monitor:

add global variables

add global variables

The dialog has a filter functionality. Select the variables which shall be monitored:

Select Symbols

Select Symbols

The update frequency in milliseconds is configured in the view:

Update Frequency

Update Frequency

With the ‘play’ button pressed, the variables in the list get updated with the specified update frequency. Changed values are marked with yellow background:

Update Variales while running

Update Variables while running

The view has a ‘Details’ pane: selecting one or more lines shows a graph of the variable over time:

Graphing Variables

Graphing Variables

The data can be plotted in different formats:

Show Details

Show Details

including a list of values which can be exported too:

List of Values

List of Values

Happy Variabling 🙂


9 thoughts on “Visualizing Global Variables while Target is Running with Eclipse and MCUXpresso IDE

  1. Hi Erich,

    I apologize for using this article to get your attention. I’ve been looking for an email address to email you directly to no avail. I posted about my issue on NXP forum community about using MCU MKL28Z’s flash memory to read/write data that are needed by my product to be persistent even when powered down, in order to have the data available on power up. And sorry I’m not on twitter or IG.

    (I’ll be quoting below to my nxp forum question/post with the hope that I can get your attention & answer me there too besides directly emailing me.)

    I just found your old blog,, about reading/writing data.
    It seems viable for my application but I’m on MCUXpresso IDE. I have not seen you reply to my post on NXP forum maybe because it’s under a different category?

    Do you mind emailing me directly &/or responding also to my question at this link:

    For any project in MCUXpresso, under Properties, there’s the C/C++Build -> MCU settings -> Default LinkServer Flash Driver Memory Map. Based on your example, I wonder if I need to MODIFY (“Split’ button) the Flash Area so the flash program space will separate from the planned data flash space?
    Also under Debug Configurations (I use PEmicro Debugger) -> Debugger tab – Advance Options button, on the pop-up window, there is option to “preserve” non-volatile memory by range from & to boxes.
    The Flash memory range of MKL28Z is 00000000-0007fffh. Do I just define a memory block within that range that I know should be protected from flash erasure & code programming by using that “advance” options under debug configurations?
    Outside of debugging, how will this allocated data memory space pan out when binary code flashing with standalone programmers?
    Is the data range now based on what’s defined in my FIRMWARE in a header .h file, by HARDCODING those addresses to read/write from & creating special function calls in a source .c file like you have done in your example?

    Please advise.

    Thanks for the help.


  2. Yes, Erich, I saw & responded there. Great info & related post links. I’m devouring all right now. If you see the “Memory details” window screenshot on my recent response this morning, it shows how it is in MCUXpresso very similar to your article how you did it in PE. …


  3. … P.S. and sorry I just saw your contact info… I went there yesterday but I did NOT scroll down the page :-(… see you over at NXP post. Thanks so much!!!


  4. … P.S. I just saw your contact info now… I went to About yesterday but I did not scroll down at the bottom… sorry 😦 See you over at the NXP posted question… Thanks so much for all the clear articles. You are truly a very good professor/teacher.

    Liked by 1 person

  5. Pingback: Enable Default FreeRTOS Debugging for LinkServer Debug Connections | MCU on Eclipse

  6. Pingback: Visualizing Data with Eclipse, gdb and gnuplot | MCU on Eclipse

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