How to use NXP MCU-Link as debug tool with LPC1769 target?

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The MCU-Link by NXP is a low-cost SWD probe that supports the CMSIS-DAP protocol and interfaces to most NXP LPC chips.
How could I set up platformio to use it as a custom debug tool?

I tried setting

debug_tool = cmsis-dap
upload_protocol=cmsis-dap

, but that didn’t work, nothing gets uploaded and debugging doesn’t work.

The target application board isn’t one on the available list of boards in platformio.
It’s an MKS-SGEN 3D printer controller with LPC1769 and an SWD connector.
The code is Marlin firmware with framework=arduino and platform=arduino-lpc176x
and it builds just fine, I just can’t upload and debug with the MCU-Link.

Side note: I was able to do a custom debug setup using an STLink probe, by setting the debug_server to call openocd with a customized board.cfg. This worked, but I picked up one of these MCU-Links and would like to use that instead,

I assume at minimum a custom board.cfg needs to be created?

Could someone describe what other steps need to be taken to get this working?

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If that’s true then check if openocd can manually use thast interface and conncect to the chip. Does something like openocd -f interface/cmsis-dap.cfg -f target/lpc17xx.cfg work with the Openocd version found in C:\Users\<user>\.platformio\packages\tool-openocd\bin?

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Thanks Max, this actually worked! It uploaded and started the debugger.

Now I just have to track some issues with the debugging, cause I keep getting errors like these:

I can set and break at a breakpoint and single step a few times, but “step into” fails and
there are numerous and random errors following that:

“could not read memory at 0xffff0000”
“target was not halted when step was issued”
and
“received SIGINT 0x00000000 isr.vector{}”

When I hit restart or run again, it always breaks on a USART TX routine even though I set no breakpoints! It’s stuck there forever until I close the session and start over again.
Could the problem be that there are a lot of interrupts coming in and the debugger just can’t handle that? (I know that debugging slows things down a bit, so maybe the incoming USART data is too much in a debug environment.)