PN7642 J-link could not read CPUID register

[trevorh]

Hello,

I am trying to connect to a PN7642 (PN7642EV/C101) in a custom PCB through SWD. I am using a J-link ultra+ debugger. The PN7642 should have only stock firmware and hasn't been used yet. I am hitting an error that I've copied in below. From my understanding of the error, the debugger can access the SOC generally but can't connect to the CPU, implying the PCB layout is ok.

Following the response to a similar error on this forum I tried to copy an .bin file via USB mass download mode. I deleted CRP_00.BIN and copied in the led-blinky .bin file from the SDK, but nothing seemed to happen - no blinking, and I still can't connect with the J-link. 

I would try to update the secure firmware, but from AN13134 it seems the LPC55S16-EVK is needed to do that.

Any advice welcome thanks,

Trevor

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)

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)

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.

[KellyLi]

Hello @trevorh 

Two suggestions to you:

1) you can try to run any SDK example on MCUXpresso IDE, to check whether your J-link works or not.

2) Update FW also can run SDK project, as the follow:

PN7642_MCUXpresso_SDK_02-15-00_PUB

\boards\pnev7642fama\demo_apps\secondary_bootloader, but before updating, please see the Readme.

[trevorh · Accepted solution]

Hi Kelly,

Thanks for the reply.

I ended up fixing this myself today. The issue was that USB_VBUS needed to be grounded to enable SWD. Some previous posts in this forum had mentioned similar issues, but I didn't realize that USB mass download mode was a blocking action that prevented SWD from working.

I'm still not sure why my example application .bin file uploaded via USB mass download didn't work, but it's a minor issue at this point.