jonr wrote:The drag and drop feature in DAPLink requires custom flash writing code for each target processor. So it's far from being a universal adapter that (fully) works with a large number of MCUs.
IMO, DAP42 gets bonus points for being more open.
DAPLink does both target-agnostic CMSIS-DAP and the target-specific drag-and-drop flashing, so it's not really a limitation (the normal use-case is to place directly on a development board, but some of them have external debug connectors that can be repurposed to debug other boards).
In terms of openness, I think it's really just a difference of priorities. The DAPLink/mbed HDK firmware is primarily written by ARM/mbed and their industry partners, so using a commercial IDE is a logical choice for them.
They're probably already paying for license keys, support, and licensed middleware (some of which has been partially open sourced in order to include in the mbed HDK project).
It's theoretically possible to make it to build with gcc - they already have a build system that can generate Makefiles.
The particularly un-fun bits are writing shims to make the armcc-specific compiler features work with gcc. I spent a few hours poking at it before deciding that becoming an expert in differences between armcc and gcc was not very rewarding.
In the mean time, I may just borrow their open source drag-and-drop implementation and see if it fits in my project.