Known Issues or Limitations

The following is a list of known issues in Qt for MCUs 1.8. For workarounds or information about the status of these issues, contact Qt Support.

To view all user-reported issues, visit the Qt for MCUs public bug tracker.


  • Development host environment support is limited to Windows 10.

Qt Quick Ultralite

  • Qt Quick Ultralite is a subset of Qt Quick and as such does not provide all the base and control QML types, which are available on the non-MCU platforms. Refer to Qt Quick Ultralite vs Qt Quick and Differences between Qt Quick Ultralite Controls and Qt Quick Controls for more information.
  • EventQueue::postEvent is not interrupt safe.
  • Charts currenty can be drawn only to an RGB32 or ARGB32 surface.
  • The Text type does not properly render unicode sequences that require complex text layout. Use StaticText for complex text.
  • SequentialAnimation and ParallelAnimation do not start automatically when assigned to a property using the "on" syntax. Explicitly set the running property to true to start the animation.
  • Setting Item::visible changes the visibility of child items but does not update the visible property of those items.
  • Text::font.pointSize does not respect screen DPI. Recommend using Text::font.pixelSize instead.
  • The default state has some limitations. Refer to Default state limitations for more information.
  • States where multiple PropertyChanges or AnchorChanges target anchor properties on the same item will not work as expected. Use a single PropertyChanges instead.
  • Setting anchors to undefined does not restore previous position and size bindings.
  • A RotationAnimation in a transition may apply to non-rotation properties. Use PropertyAnimation::properties instead.
  • All delegates in a ListView must have the same size. The size must be explicitly specified and cannot be dynamically changed.
  • onPropertyChanged is not supported for grouped properties.
  • The JavaScript Date object returns the elapsed time since the application started, instead of the current date and time.
  • The scale, rotation, and transformOrigin properties are only generated if they have bindings. For example, if an item's scale is not explicitly declared with an initial value, setting item.scale = 2 results in a compilation error. This can be resolved by adding the scale: 1 binding to the item.
  • Bindings on color value accessors are not supported.
  • Using the clip property on transformed items is not supported.
  • Transforms on an item do not apply to the item's children. Individually set transforms on each child instead.
  • RGB332 pixel format is not supported by any of the reference boards. It can be only used for the desktop backend and for the custom hardware.
  • Font property bindings are supported only when using the Spark font engine. See Text Rendering and Fonts for details.

Qt Creator

  • When editing Qt Quick Ultralite QML files, the following errors are displayed in the Issues panel and highlighted in the code editor. They can safely be ignored:
    • package import requires a version number

      A version number can optionally be added but is not strictly required in Qt Quick Ultralite.

    • Unknown component for ColorizedImage and StaticText

      Set the QML_IMPORT_PATH variable in your CMake project file to the location of the QUL compatibility module to solve this issue.

  • QML debugging is not supported
  • QML profiling is not supported

Qt Design Studio

  • On-device preview is not supported. To preview the design on your MCU board, use the auto-generated CMake project and compile it using Qt Creator.
  • Qt Quick Ultralite-specific QML types (StaticText, ColorizedImage) are not available in the component library.

Renesas RH850

The following is a list of known issues on the Renesas RH850 hardware.

  • The internal ROM is used to store code (data and text) and the graphical assets only. This limits the size of the executable to be not more than 5 MB.
  • Qt Quick Ultralite 1.8 does not enter low CPU power mode. If no frame is rendered and no other tasks are running, Qt Quick Ultralite loops until next frame needs to be rendered or another task needs CPU time.
  • The Monotype Spark font engine (Technology Preview) is not supported.


The following is a list of known issues on the STM32H750B hardware.

  • Screen may flicker while performing double precision operations. For that reason, qreal defaults to float instead of double.
  • The SDK version 1.6.0 is not supported yet.

NXP i.MXRT1050 and NXP i.MXRT1064

The following is a list of known issues on the NXP i.MXRT1050 hardware.

  • When debugging, interrupted program won't resume its execution and must be restarted by using the mon reset halt command.


  • To work around a GNU Arm Embedded Toolchain bug (https://bugs.launchpad.net/gcc-arm-embedded/+bug/1747966), all the object files and libraries are passed to ld in a linker group (using --start-group/--end-group). Additionally, libraries are passed to linker before application object files, which is opposite to default behavior.

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