Hello Nordic Support,
I need version-specific troubleshooting advice for an nRF52840 DK, PCA10056 hardware v3.0.3 (label 2026.16), with the nRF5340 interface MCU. I have not yet been able to use its onboard debugger.
Current isolated setup:
- Only J2 / IMCU USB is connected to the computer. External target/P19 connections are disconnected.
- SW6 = DEFAULT, SW9 = VDD, SW8 = ON.
- LED5 currently stays off. Earlier during troubleshooting it sometimes flashed rapidly; the current symptom is off.
- On an Apple Silicon Mac, the USB device tree does not show a J-Link or Nordic device (not merely a missing serial port).
- Tried multiple cables, direct connection and a USB hub. The same cable and Mac port successfully enumerated a Vivo phone. Another computer also gave no detection indication, although its full USB device tree was not recorded.
DC measurements relative to GND:
- TP36 = 5.02 V (V5V)
- TP37 = 3.0 V (VDD)
- TP35 = 3.0 V (VDD_IMCU)
These net names are from the v3.0.3 hardware schematic. VBUS_IMCU, USB_DETECT and IF_OFF have NOT been measured. Thus I am not assuming the USB supply path through U24 is working.
No solder bridges have been modified, and no interface-MCU erase/recover or firmware update has been performed. I want to avoid erasing the interface MCU bootloader or using legacy SAM3U firmware.
Could an engineer please advise:
1. The safest accessible measurement points and expected voltages for VBUS_IMCU, U24 input/output and its control on this exact revision. Could that path explain both LED5 off and no USB enumeration while VDD_IMCU is 3.0 V?
2. Whether SB30 on the actual v3.0.3 schematic provides a non-erasing interface-MCU reset, and whether you recommend testing it. No bridging has been attempted.
3. Is there any supported recovery/update procedure for the nRF5340 onboard probe when it is completely absent from the USB device tree? Does RESET-at-power-up apply to this revision?
4. If the measurements above indicate service is needed, should I arrange a distributor replacement instead of modifying the board?
Related cases found, but not assumed to diagnose my board:
- v3.0.2 user-reported U24 / SB48 workaround: devzone.nordicsemi.com/.../nrf52840dk-v3-0-2---solution-for-flashing-led5-and-no-detection-over-usb
- v3.0.3 bootloader/update failure: devzone.nordicsemi.com/.../pca10056-rev-3-0-3-2026-7---j-link-ob-nrf5340-stuck-in-bootloader-firmware-update-always-fails
The second case initially had a detectable bootloader; mine currently has no USB enumeration. I have not applied either case's workaround.
Thank you.
