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Arm Mbed DAPLink is an open-source software project that enables programming and debugging application software running on Arm Cortex CPUs. Commonly referred to as interface firmware, DAPLink runs on a secondary MCU that is attached to the SWD or JTAG port of the application MCU. This configuration is found on nearly all development boards. Enumerating as a USB composite device, it creates a bridge between your development computer and the CPU debug access port. DAPLink enables developers with:

  • MSC - drag-n-drop programming flash memory
  • CDC - virtual com port for log, trace and terminal emulation
  • CMSIS-DAPv2 WinUSB (driver-less vendor-specific bulk) - CMSIS compliant debug channel
  • CMSIS-DAPv1 HID - CMSIS compliant debug channel
  • WebUSB CMSIS-DAP HID - CMSIS compliant debug channel

More features are planned and will show up gradually over time. The project is constantly under heavy development by Arm, its partners, numerous hardware vendors and the open-source community around the world. DAPLink has superseded the mbed CMSIS-DAP interface firmware project. You are free to use and contribute. Enjoy!

For more detailed usability information see the users guide.


There are many ARM microcontroller-based Hardware Interface Circuits (HICs) that DAPLink interface firmware runs on. These can be found as standalone boards (debugger) or as part of a development kit. Some branded circuits that are known to be IO compatible are:

You can find more information on the microcontrollers supported here.


There are many board builds (board = HIC + target combination) created from this repository. Quarterly releases will contain new features and bugfixes. Standalone bugfixes are released once reported, verified and fixed. Both quarterly and bugfix releases will result in the build number being incremented. Many development kits and products ship with DAPLink interface firmware or are capable of running DAPLink firmware. The current release builds and instructions for updating DAPLink interface firmware is hosted on the DAPLink release site. Release notes and previous release builds can be found under GitHub releases.


We welcome contributions to DAPLink in any area. Look for an interesting feature or defect under issues. Start a new thread in the discussions or in Slack to engage with the developers and maintainers.

Please see the contribution guidelines for detailed requirements for contributions.

To report bugs, please create an issue in the GitHub project.


Information for setting up a development environment, running the tests or creating a release build can be found in the developers guide.


DAPLink is licensed with the permissive Apache 2.0 license. See the LICENSE file for the full text of the license.

Copyright © 2006-2023 Arm Ltd