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Upgrading the BBC micro:bit DAPLink to J-Link

 J-Link Firmware upgrade for BBC micro:bit

SEGGER offers the capability to upgrade the firmware on the BBC micro:bit DAPLink to a J-Link OB (On Board). This firmware makes the on-  board debug solution on the BBC micro:bit compatible to J-Link, allowing  users to take advantage of all J-Link features such as ultra fast flash  download and debugging speeds and the free-to-use GDBServer as well  as application development using an IDE. 


  • Fully compatible to J-Link offering the same features.
  • Enables full featured development with Embedded Studio IDE
  • Using J-Link enabes the use of a broad range of IDEs.
  • Maintains support of HEX file Drag and Drop.
  • Getting started Demo project for Embedded Studio provided.


BBC microbit J-Link upgrade BBC microbit J-Link upgrade

This video walks through the steps needed to upgrade the BBC:microbit DAPLink to a SEGGER J-Link.


SEGGER's J-Link OB firmware update for the BBC micro:bit platform, makes it fully J-Link compatible.

In order to make use of this firmware, the following Terms Of Use must be accepted:

  • The firmware may only be used for development and/or evaluation purposes. It may not be used for production purposes.
  • The firmware is ONLY for use with BBC micro:bit boards and boards based on the micro:bit Reference Design (, provided that firmware on the micro:bit Reference Design is only used for non-commercial purposes (e.g. education, evaluation, ...). The firmware running on a micro:bit hardware may also be used to program the debug interface firmware (J-Link OB firmware, DAPLink, etc.) into hardware based on the micro:bit reference design
  • The firmware is made available without any warranty and without support from SEGGER.
  • No production flash programming support

If there is any doubts or concerns on a specific use case it is recommended to contact SEGGER prior to use.


When starting a debug session, a license dialog pop-up appears which must be accepted before the J-LINK OB can be used:


The BBC micro:bit J-Link OB firmware has some limitations when compared to the full featured industry leading SEGGER J-Link. These are detailed here:

By using an original SEGGER J-Link PROJ-Link ULTRA+ or J-Link PLUS, all these limitations are removed. Learn more about J-Link here.

Getting Started

Just a few easy steps are needed to upgrade the firmware on the BBC micro:bit DAPLink to a J-Link OB:
  1. Make sure that the latest J-Link software package is installed: J-Link software package download.
  2. Take the BBC micro:bit and hold the reset button pressed while connecting it via USB to the PC. This will start it in maintenance mode which allows firmware updates.
  3. The micro:bit will appear as mass storage device (MSD) on the PC as shown below.
  4. Download and extract the J-Link OB firmware from this page (below)
  5. Load the firmware - simply drag & drop the J-Link OB firmware (*.hex file) on to the MSD device.
  6. After the file transfer is complete, power-cycle the micro:bit, this time without the reset button pushed
  7. The micro:bit will now show up as J-Link on the PC.
  8. To verify the connection to the micro:bit use the J-Link Commander which is a command line utility that comes with the J-Link software package

Getting started - Sample projects

There are sample projects available for the BBC micro:bit that can be compiled, downloaded an debugged with SEGGER Embedded Studo. The sample projects are available for download in our downloads section:

Firmware Image

The Firmware image to convert the on-board debug interface of the micro:bit to a J-Link OB, can be downloaded from our download section:

Firmware Version History


  • Added support for VCOM


  • Initial version