SEGGER RTT Viewer connection latches device to high power if not disconnected

[MortenK]

Hi,

We noticed that if you do not "Disconnect" a SEGGER RTT connection (on the RTT Viewer), the nRF52832 chip latches into using a relatively large amount of power (~3mA).
This appears to be maintained even through a pin reset. A full power cycle is required to go back to low power modes.

Some details:

- Using NCS 2.5.1. nRF52832.

- We aren't using the RTT for logging. Custom buffers using SEGGER_RTT_Write() and SEGGER_RTT_Read()

- We have tried both:

• Enabling zephyr,pm-device-runtime-auto in device tree
• Manual calls of form:  pm_device_action_run(DEVICE_DT_GET(DT_ALIAS(rtt0), PM_DEVICE_ACTION_SUSPEND);

Is there a way to disable this interface/revert to low power modes via the application if no clean disconnection is detected?

[Håkon Alseth]

Hi,

 

The debugger cannot be directly detected or detached from the nRF52-side. This is an operation that must be performed on the PC side.

If the debugger attaches, it will force power and clock domains on.

 

Is there a way to disable this interface/revert to low power modes via the application if no clean disconnection is detected?

JLinkRTTViewer shall do a clean-up and not keep the debugger in a connected state. I would recommend that you update your jlink installation and see if this behavior changes.

  

Kind regards,

Håkon