10 years, 6 months ago.

I am not the expert and my understandings are:

1). CMSIS-DAP defines a bunch of DAP commands to access the micro controller. The hardware debugger that support CMSIS DAP should be able to support those DAP commands. Through those DAP commands, most debug features required by software MCU developers can be achieved.

2). A brief process would be like: software developer input gdb command like "load" under gdb, a gdb server figures out what DAP commands are needed to finish this "load" command, then gdb server enclose DAP command along with data in USB packet and send it to hardware debugger over USB cable, hardware debugger decode the USB packet and get DAP command and data, and then hardware debugger do the final job through debug access port of MCU. Possible the "load" command requires more than one DAP commands, so the gdb server talks to hardware debugger more than one times.

3). With CMSIS DAP, it becomes easy to implement a software debugger server.

4). There is CMSIS-DAP Beta 0.01 package at https://silver.arm.com/browse/CMSISDAP. Among which you can find what standard DAP commands are defined, some example firmware projects that enable hardware debugger to support DAP.

10 years, 6 months ago.

Would mbed.org share the source code of the mbed interface firmware? I found it is also implemented based on CMSIS-DAP.