DAPlink is an open source project that implements the embedded firmware required for a Cortex debug probe. The project is hosted on Git Hub, and is published under an Apache 2.0 license, making it attractive for commercial developments.

The software project is complemented by a series of reference designs for creating the DAPLink debug probe hardware, which are available in the mbed HDK.

DAPLink Features

A DAPLink debug probe connects to your host computer through USB, and connects to your target system (the one to be programmed and debugged) through a standard Cortex debug connector. It provides three main features all over a single USB connection.

HID interface

The driver-less HID interface provides a channel over which the CMSIS-DAP debug protocol runs. This enables all the leading industry standard toolchains to program and debug the target system. Supported tools include :

  • Keil MDK
  • IAR Workbench
  • pyOCD

USB Disk drag and drop programming

DAPLink debug probes also appear on the host computer as a USB disk. Program files in binary (.bin) and hex (.hex) formats can be copied onto the USB disk which then programs them into the memory of the target system.


The DAPLink probe needs to contain the programming algorithms specific to the target system. Therefore, the version of the DAPLink firmware being used must match the target system.

USB Serial Port

The DAPLink debug probe also provides a USB serial port which can be bridged through to a TTL UART on the target system. The USB Serial port will appear on a Windows machine as a COM port, or on a Linux machine as a /dev/tty interface.

For more information on configuring your host computer to use this feature, please see :

Git Hub repository for DAPLink

Debug probes built with DAPLink