Hi Folks & experts
I hope you ALL are well.
I wanted to share a bring-up result from my XIAO nRF54LM20A workbench and ask for your guidance.
I have the XIAO nRF54LM20A mounted on the Seeed expansion board and connected by external SWD to the P19 external-debug port of an nRF54L15 DK. The nRF54L15 DK onboard J-Link connects to the LM20A reliably:
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Target selected: nRF54LM20A_M33
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SWD-DP detected: 0x6BA02477
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Cortex-M33 identified
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Secure debug enabled
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Halt, register reads, and memory reads all work
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RTT/UART output works after programming
I built a Zephyr/NCS v3.2.1 hello-world/demo application using the Seeed XIAO nRF54LM20A board files. Nordic nrfutil programs the resulting merged.hex successfully through the same nRF54L15 DK probe:
nrfutil device program --firmware C:\ncs\v3.2.1\build\merged.hex --serial-number 1057729516
After reset, the application runs and produces serial output, including LED and IMU data.
The issue is with direct J-Link Commander flash operations. I tested current J-Link software, including V9.30a, with the nRF54L15 DK onboard J-Link firmware dated July 8, 2025. J-Link Commander can connect and debug the LM20A, but both erase and loadfile fail with:
“Timeout while preparing target, RAMCode did not respond in time!”
“Failed to perform RAMCode-sided Prepare()”
This happens at 500 kHz SWD as well as 1 MHz. Because nrfutil programs the same target successfully through the same physical setup, the wiring, target power, SWD access, build artifact, and basic debugger path appear sound.
SEGGER’s supported-device information indicates nRF54L-family support, so I am trying to determine whether this is:
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a limitation or defect in the J-Link flash-loader/RAMCode path for nRF54LM20A,
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a requirement for Nordic-specific initialization that nrfutil performs, or
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a limitation of using the nRF54L15 DK onboard J-Link as an external probe for the LM20A.
I can provide full J-Link logs, the merged.hex, board files, and screenshots if helpful.
same result with J-Link commander Ver. 8.94
Thank you,
PJ Glasso
PS. same tech has always worked, nRF52840, nRF54L15. it does flash, but only with nRFutil, not J-Link, Debug works?