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FRDM-iMX93: MCU-Link Pro cannot connect to Cortex-M33 core via SWD

Hi all,

I have recently started developing with a FRDM i.MX 93 and purchased an MCU-Link Pro for Cortex-M33 debugging. I am trying to set up M33 debugging using the MCU-Link Pro connected via a SWD adapter to the external debug pin header on the board.

Setup:

Board: FRDM-IMX93 (MIMX9352)
Probe: MCU Link Pro with SWD Adapter
IDE: MCUXpresso for VS Code
SDK: SDK_26_06_00_MIMX9352xxxxM

Problem:

After doing a firmware update on the probe, it is being recognised correctly by LinkServer, but when I try connecting to the M33 core it fails with Ee(42). Could not connect to core.

What I've done:

Connected the header pins correctly(P14) to the adapter and selected the right debug port on the MCU Link Pro (J7).
Disconnected the R3017 & R3018 resistors.

Exported the hello_world example from the SDK, built it successfully, and attempted to start a debug session in MCUXpresso for VS Code but it fails immediately:

My launch.json configuration is the following:

{
  "configurations": [
    

    {
      "type": "mcuxpresso-debug",
      "name": "Debug",
      "request": "launch",
      "cwd": "${workspaceFolder}",
      "executable": {
        "elf": "${workspaceFolder}/debug/mcimx93evk_hello_world_cm33.elf"
      },
      "stopAtSymbol": "main",
      "probeSerialNumber": "WWCHLV4PL2JZX",
      "isAttach": true,
      "skipBuildBeforeDebug": false,
      "gdbInitCommands": [
        "set remotetimeout 600",
        "set debug-file-directory",
        "set non-stop off"
      ],
      "gdbServerConfigs": {
        "linkserver": {
          "device": "MIMX9352:MCIMX93-EVK"
        },
        "segger": {},
        "pemicro": {}
      },
      "showDevDebugOutput": "none"
    }
  ]
}

Ran the LinkServer GDB server from the command line and got the following output (key lines highlighted below):

INFO: Selected device MIMX9352xxxxM:MCIMX93-EVK
INFO: Selected probe #1 WWCHLV4PL2JZX (MCU-LINK Pro (r1CF) CMSIS-DAP V3.172)
INFO: Firmware update: not required
GDB server listening on port 2332 in debug mode (core cm33)
INFO: Connected to core cm33
...
Wc: DpID = 00000000           <-- SWD DP ID reading as zero
Wc: Error: Wire not connected  <-- repeated throughout
Wc: Error: Wire not connected
Wc: Error: Wire not connected
...
Wc: ... send a request to EdgeLock secure enclave to release the Cortex-M33 TROUT
Wc: Resp1 : 0x000000C8
Wc: Resp2 : 0x000000C8
Wc: SCR = 0x000000C8
Wc: M33 kicked off
Wc: Error: Could not read registers (0xA5)
...
Ed:02: Failed on connect: Ee(42). Could not connect to core.
Et:31: No connection to chip's debug port
INFO: Disconnected from core cm33

The full repeated Error: Wire not connected and DpID = 00000000 suggest the SWD physical connection is not working, even though the ELE (EdgeLock enclave) responses appear non-zero.

Tried different boot mode switch settings on the board.
Tried this guide and got to the Flash the Binary using UUU Tool step, but when I tried starting fastboot I got the following error:
```
Failed to configure default pinctrl
```
This stopped progress on that path as well.

Questions:

DpID = 00000000 and Error: Wire not connected: is this a physical wiring fault, or can it also indicate the M33 is still held in a state where SWD is not reachable even after R3017/R3018 are removed?
Does VTref need to be connected on the MCU-Link Pro SWD adapter for this board? Could a missing VTref cause this symptom?
If VTref need to be connected, does it need to be connected to a 3V3 or a 1V8 (it is a topic that has been raised frequently on forums)?
Is P14 + J7 the correct header/port combination for M33 SWD access on the FRDM-IMX93, or is there another configuration that needs to be done on the MCU Link Pro and I have missed it?
The ELE responses show 0xC8, does that value indicate a problem with releasing the M33?
Regarding the UUU fastboot error (Failed to configure default pinctrl), is there a specific U-Boot image or boot switch configuration required for fastboot to work on the FRDM-IMX93?

References & resources I consulted:

Before posting I went through the following resources, which shaped the steps I tried:

Any guidance or a working configuration example would be greatly appreciated.

Thanks in advance!

Re: FRDM-iMX93: MCU-Link Pro cannot connect to Cortex-M33 core via SWD

Hi @AndreeaPascu,
Thank you for contacting NXP Support!

To debug the i.MX93 FRDM, you must first remove two resistors that interfere with the SWD signals. Without this modification, the debugger may not be able to communicate properly with the target device.

Another important point is that, by default, the MCU-Link Pro must be flashed with the Segger firmware before it can be used to debug the i.MX93. Once the Segger firmware is installed, the MCU-Link Pro can be used as a standard J-Link debug probe.

I published the following guide describing all the required hardware modifications and software setup steps needed to debug the i.MX93 using the MCU-Link Pro. I hope you find it useful:

Getting Started with FRDM-IMX93 and MCU-LINK Pro for M Core Debugging

Best regards,
Chavira