[ABANDONED] Atmel SAMD21E16B lockup in STANDBY mode: What does "could not power-up debug port" mean?

pieterc · May 23rd 2016, 11:11am

Hi there!

I am trying to debug a very tricky problem. Under rare circumstances the Atmel SAMD21E16B locks up and does not want to wake up from STANDBY sleep mode from an external interrupt source. It does not look like any code is executed, not even the interrupt handler code, because I toggle a debug pin in the interrupt handlers and the main code.

I tried debugging using a J-Link, but I get the following error message: "Error: SAMD (connect): Could not power-up debug port". It does report however "Found SWD-DP with ID 0x0BC11477". See attached screenshot.

Any hints or tips? What does "could not power-up debug port" mean?

Thanks in advance,
Pieter

SEGGER - Alex · May 24th 2016, 11:29pm

Any hints or tips? What does "could not power-up debug port" mean?

It means what it says... The debug port could not be powered up.
There are two power domains in ARM Coresight debug:
Debug power domain (Handles access to the DP registers)
System power domain (Handles access to the AP registers)
Power to them is enabled by setting two bits in the Ctrl/Stat register of the JTAG-DP / SW-DP.
However, if they can be powered up or not, depends on the state of the device. Many devices ignore these bits when they are in low power modes, so the debug probe has no chance to get access to the target again. Bug in debug design...

Do you have the nRESET pin of the CPU connected to J-Link?
If yes, J-Link has a chance to get access to the device again by performing a "connect under reset".
If you don't, you are out of luck.

Best regards
Alex

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