CMSIS-DAP is a 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.

CMSIS-DAP Overview

Configuration of CMSIS-DAP Firmware

The CMSIS-DAP Firmware version 2 can be configured in two different USB interface modes:

Version 1 configuration uses USB HID as interface to the host PC.
Version 2 configuration uses WinUSB as interface to the host PC and provides high-speed SWO trace streaming.

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 of Cortex-M devices (new in CMSIS-DAP Version 1.1.0).
Easy to deploy to Debug Units based on Cortex-M microcontrollers.
Debug Unit may be integrated on an evaluation board.
USB using HID (Human Interface Device) driver class that avoids driver installation on host PC.
Supports time-critical JTAG or SWD command execution (new in CMSIS-DAP Version 1.10).
Supports Test Domain Timer for time measurement using the debug unit (new in CMSIS-DAP Version 1.2.0)

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 Software Stack is composed of the following components:

CMSIS-DAP Firmware that interfaces to JTAG or SWD Debug 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.
USB Communication Stack that interfaces to the USB Port of the Host Computer using the HID or custom class.
The USB Device middleware may require CMSIS-RTOS and a CMSIS-Driver USB.

CMSIS-DAP Software Stack

In the examples provided the MDK Version 5 USB Communication Stack has been used. However it is possible to use alternative USB stacks instead.

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 Version 5 middleware

Debug Access

Note: Arm plans to provide the RDDI-DAP Access DLL that connects a debugger to the CMSIS-DAP Firmware. However as the DAP registers are standard in all Cortex devices, the debug access is well understood by the industry.

Validation

CMSIS-DAP compliant Debug Units must be validated using the scripts provided in Validate Debug Unit.