CMSIS-DAP is a protocol specification and a implementation of a firmware that supports access to the CoreSight Debug Access Port (DAP).The various Arm Cortex processors provide CoreSight Debug and Trace. CMSIS-DAP supports target devices that contain one or more Cortex processors. A device provides a Debug Access Port (DAP) typically either with a 5-pin JTAG or with a 2-pin Serial Wired Debug (SWD) interface that connects to a debug unit. CMSIS-DAP is the interface firmware for a debug unit that connects the debug port to USB. Debuggers that execute on a host computer connect via USB and the Debug Unit to the device which runs the application software.

Benefits of CMSIS-DAP

Provides a standardized interface for debuggers. Interfaces to many standard debuggers is available.
Access to CoreSight registers of all Cortex processor architectures (Cortex-A/R/M).
Connects via 5-pin JTAG or 2-pin Serial Wire Debug (SWD).
Supports multi-core debugging.
Supports Serial Wire Output (SWO) of Cortex-M devices.
Easy to deploy to debug units based on Cortex-M microcontrollers.
Debug unit may be integrated on an evaluation board.
Using USB bulk transfers avoids driver installation on host PC.
Supports time-critical JTAG or SWD command execution.
Supports Test Domain Timer for time measurement using the debug unit.
Supports UART communication port, which can be routed to USB COM Port (optional) or native CMSIS-DAP commands (new in CMSIS-DAP Version 2.1.0).

CMSIS-DAP firmware

The CMSIS-DAP firmware is provided as source code and is fully configurable to a new debug unit. A source code template and several reference implementations for popular debug units are provided. Refer to Firmware configuration for more information.

The CMSIS-DAP firmware stack is composed of the following components:

CMSIS-DAP firmware that interfaces to JTAG or SWD pins using standard I/O pins of the Cortex-M device.
CMSIS-Driver USART that connects:
- the UART of the Cortex-M device to the SWO output from the target.
- an additional UART of the Cortex-M device to the UART from the target.
USB stack that interfaces to the USB port of the host computer using:
- a custom class (for USB bulk endpoints),
- the CDC ACM class to export USB COM Port.
The USB Device middleware may require CMSIS-RTOS and a CMSIS-Driver USB.

In the examples provided, the MDK-Middleware USB stack has been used. However, it is possible to use alternative USB stacks.

Note

CMSIS-DAP v1.x is deprecated and not recommended for new designs.
Use CMSIS-DAP v2.x instead that provides high-speed SWO trace streaming and does not require driver installation in modern operating systems (Mac OS, Linux, Windows). Refer to Installing CMSIS-DAP enabled debug adapters for more information.

Validation

CMSIS-DAP compliant debug units must be validated using the scripts provided in Validate the debug unit operation.

The CMSIS-DAP firmware is provided in the following directory structure.

Directory	Description
.\CMSIS\DAP\Firmware\Config	CMSIS-DAP firmware configuration
.\CMSIS\DAP\Firmware\Examples	CMSIS-DAP firmware adapted to various debug units
.\CMSIS\DAP\Firmware\Include	CMSIS-DAP firmware header file
.\CMSIS\DAP\Firmware\Source	CMSIS-DAP firmware source code
.\CMSIS\DAP\Firmware\Template	Interface templates for MDK-Middleware
.\CMSIS\DAP\Firmware\Validation	Validation project