J-Link Commander Cannot Download Image to PN7642 (Some Units Previously Working Now Failing)

[axis-zhao]

Hi all,

I'm encountering an issue when using J-Link Commander to download firmware to the PN7642 .

Summary:

* Total units: 36

* 22 units: working normally

* 14 units: consistently failing

Important note:

All units were previously programmed successfully with our earlier firmware. The issue appeared when attempting to reprogram them with a newer image.

Issue description:

For the failing units, J-Link Commander cannot connect to the target device. The log output is shown below:

```

Connecting to target via SWD
Found SW-DP with ID 0x6BA02477
DPIDR: 0x6BA02477
CoreSight SoC-400 or earlier
Scanning AP map to find all available APs
AP[1]: Stopped AP scan as end of AP map seems to be reached
AP[0]: AHB-AP (IDR: 0x84770001, ADDR: 0x00000000)
Iterating through AP map to find AHB-AP to use
AP[0]: Skipped. Could not read CPUID register
Attach to CPU failed. Executing connect under reset.
Failed to power up DAP
Found SW-DP with ID 0x6BA02477
DPIDR: 0x6BA02477
CoreSight SoC-400 or earlier
Scanning AP map to find all available APs
AP[1]: Stopped AP scan as end of AP map seems to be reached
AP[0]: AHB-AP (IDR: 0x84770001, ADDR: 0x00000000)
Iterating through AP map to find AHB-AP to use
AP[0]: Skipped. Could not read CPUID register
Attach to CPU failed. Executing connect under reset.
Failed to power up DAP
Error occurred: Could not connect to the target device.
For troubleshooting steps visit: https://wiki.segger.com/J-Link_Troubleshooting
```

Additional information:

• I have tried issuing the r (reset) command in J-Link Commander, but it does not resolve the issue
• Same hardware setup is used for both working and failing units (same J-Link, same board, same procedure)
• All failing units show identical behavior

Observations:

• Failure occurs during SWD connection:
  • Cannot read CPUID
  • DAP power-up fails
• Working units remain fully programmable

Questions:

1. Are there known mechanisms in PN7642 that can disable or lock SWD after programming?
2. Is there a recommended way recover access (e.g., connect under reset, mass erase, boot pin configuration)?
3. Could this indicate the device entering a protected or low-power state that blocks debug access?

Any guidance on how to recover these devices or further debug the root cause would be greatly appreciated.

Thanks in advance!

[axis-zhao]

Hello @KaiLi,

Thanks for the suggestion to try J-Flash.

I've attempted to use J-Flash with my PN7642, but I'm consistently running into connection failures. The behavior is similar to what I observed with J-Link Commander - J-Flash is unable to establish a connection to the target. (See the attached file, 'j_flash_connection_error.png').

Are there any additional steps or recovery methods you would recommend to regain access?

Any guidance would be greatly appreciated!

Thanks!

I

[KaiLi]

Hello @axis-zhao 

Please try J-Flash, it works fine on my side, like attach picture.