J-Link OB is an on-board debug probe as part of YOUR eval board.

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J-Link OB is an on-board debug probe as part of YOUR eval board. The microcontroller has a USB-interface on one side and a JTAG/SWD + SWO etc. interface on the device side. It allows debugging the target device on the board it comes with, without the need for an additional debug probe. J-Link OB is used on various eval boards by several eval board manufacturers for various target CPUs.

Having a J-Link right on the eval board allows customers to fully use and test the target CPU, providing full debug capabilities. At the same time, the eval board can remain small and inexpensive. All features of the regular J-Link can be used, including download into Flash memory.

Licensing - Eval board manufacturers

J-Link OB is provided as part of an evaluation board. It is not sold separately. It may only be used to debug the device on the evaluation board it came with. Support is given via the eval board manufacturer and via SEGGER Forum. J-Link OB may not be used for production purposes.

Licensing - Commercial use

J-Link OB is designed in a product or a software development board (for setting up a automated test environment etc.). Pricing is available upon request. 

Getting started

Basic Concept

The pictures below show the connection between a PC and the target CPU using the regular J-Link and a J-Link OB.

Connection via regular J-Link:

The PC is connected to J-Link via USB and J-Link connects to the eval board via JTAG debug connector.

Drag-And-Drop Option: Intuitive Programming of the Target Device

Drag-And-Drop is a an optional J-Link OB intuitive programming feature. It allows programming your target MCU in a very simple way. 

J-Link OB with Drag-And-Drop capability appears both as a debug probe and as a flash drive on the user's computer - similar to a USB stick. The J-Link's high performance and functionality for programming and debugging remain unchanged! The additional flash drive capability simplifies programming the target to dragging a Motorola S-record, Intel Hex, or plain binary file onto the J-Link Drive using the desktop. 

J-Link Drive enables manufacturers, and third-party software developers, to deploy ready-to-go demonstration applications to customers who can then quickly evaluate the capability of the board, software, and device - all without installing complex development software. All major operating systems (Windows, macOS, Linux) are supported and existing OS drivers already support J-Link Drive. 

When customers outgrow the convenience of J-Link Drive and fixed demonstration applications, they can unleash the full potential of the target board using the J-Link OB as a debug probe backed by unparalleled, industry-wide support. 

Developed by SEGGER's Embedded Experts Team, J-Link OB offers a compelling opportunity for board manufacturers to provide a highly polished way to deliver integrated solutions to customers, and enhance the experience over time by adding new applications and features that just "drop into place".

  • NordicSemi nRF52-DK

The image below demonstrates how easy an MCU can be programmed via "Drag-And-Drop" option. 
1) Open a file explorer of your choice. J-Link will be shown as a flash drive. 
2) Drag and drop a Bin, Hex or Mot file to the J-Link drive. Programming will start as soon as you drop the file.

Please note, that Drag-And-Drop is available upon request only. 
If you are interested or need more information, please do not hesitate to contact us at info@segger.com.

Example implementations that support Drag-And-Drop flash programming

The following boards are already using J-Link OB implementations that support Drag-And-Drop flash programming: 

  • NordicSemi nRF51-DK (https://www.nordicsemi.com/Software-and-Tools/Development-Kits/nRF51-DK)

J-Link OB is intended to be licensed for evaluation board manufacturers and silicon vendors. We offer a very reasonable pricing.

Model overview / Supported cores

J-Link OB is not much more than a microcontroller with USB device interface running J-Link firmware. Below is a list of currently available options for J-Link-OB, along with the supported cores and interfaces.

Please note that not every J-Link-OB supports every core and every interface/feature. Other microcontrollers can be supported upon request. If you are looking for a combination that is not yet supported, please get in touch with us.

J-Link OB modelOB DeviceSupported target coresJTAGSWDVCOM
Drag & Drop
SWO speedInterface speedDownload performance
J-Link-OB-K22-Cortex-M NXP MK22FN128VLH10 LQFP64 package No external crystal required Cortex-M4 @ 96MHz, 128 KB flash Cortex-M





4 MHz 4 MHz 200 KB/s
J-Link-OB-K22-Cortex-A Cortex-A





J-Link-OB-STM32F072-Cortex-M-128KB ST STM32F072CB UFQFPN48 package No external crystal required Cortex-M0+ @48 MHz, 128 KB flash Cortex-M





250 kHz 2 MHz 100 KB/s
J-Link-OB-STM32F072-Cortex-M-64KB ST STM32F072C8
UFQFPN48 package
No external crystal required
Cortex-M0+ @48 MHz, 64 KB flash





250 kHz 2 MHz 100 KB/s
J-Link-OB-STM32F072-Cortex-A-64KB Cortex-A





J-Link-OB-STM32F103-Cortex-M ST STM32F103TB
VFQFPN36 package
Cortex-M3 @72 MHz, 128 KB flash





4500 kHz 2.25 MHz 150 KB/s
J-Link-OB-STM32F103-Cortex-A Cortex-A





J-Link-OB-SAM3U128 Atmel ATSAM3U2C
LQFP100 package
Hi-Speed USB
Cortex-M3 @96 MHz, 128 KB flash





12000 kHz 3.2 MHz 225 KB/s
Available, but not recommended for new designs
J-Link-OB-SAM7S64 Atmel SAM7S64
LQFP64 package
ARM7 @48 MHz, 64 KB flash





6000 kHz 12 MHz 700 KB/s
  • • Fully compatible with and same features as regular J-Link 
  • • Inexpensive solution for complete evaluation kits with debug functionality
  • • JTAG, SWD + SWO supported
  • • Virtual COM Port (K22-Cortex-M, K22-Cortex-A, STM32F072, SAM3U)
  • • Optional disable allows use of other external debug probes
  • • Compatible with most IDEs 
  • • Very small form factor
  • • "Drag-And-Drop" interface for intuitive programming of the target device