USB wakeup from Lowpower mode

[Ilam]

Hi Team,

I'm working on an application using the nRF5340, and I'm implementing a low power mode in which the system shuts down non-essential peripherals and aborts all active threads and timers. The goal is to reduce power consumption after 5 minutes of inactivity.

Requirement:
I would like the device to wake up from this low power mode when USB is connected (i.e., VBUS becomes active).

Here’s what I’ve observed:

• According to the datasheet, VBUS is connected to pin B11.

• I’m using nRF Connect SDK v2.5.2.

• When I enter system off mode using sys_poweroff(), the device wakes up when USB is connected, which is expected behavior.

• However, when I use my custom low power routine (which aborts threads, stops timers, and suspends peripherals), the device does not wake up on USB connect.

• I’m currently unable to configure B11 (VBUS) as a GPIO wake-up source, likely because it’s tied internally to the USB regulator.

Questions:

1. Is there a recommended way to detect USB connection (VBUS rising edge) during low power or standby (not just in system off)?

2. Can B11 (VBUS) be configured as a wake-up source in low power mode?

3. Alternatively, is there a recommended GPIO (or circuit-level approach) to detect USB insertion and trigger wake-up from low power mode?

Any guidance on configuring this properly in Zephyr / nRF SDK v2.5.2 would be appreciated.

Thanks in advance,
Ilam

[Vidar Berg]

Hi,

Does your low power routine also disable USB? This would prevent any USB interrupts from being triggered when it is plugged back in. What do you measure if you leave USB enabled but disconnect VBUS?

Best regards,

Vidar

[Przemek Ostrowski]

Hello.
I see similar behavior. When I enter sleep by calling: sys_poweroff(); device wake up on GPIO low level which I configured, but it also wakes up when I plug in or unplug USB. I need to know if that is the default behavior or there is something wrong with the power supply/battery charger on the board that is causing MCU reset.
I am using nRF Connect 3.1.0. I only configured wake on GPIO P0.01 and P1.10 low level.

Thank you for help.
Przemek

[Turbo J]

This should be its own ticket, but read PS chapter 4.2. Valid USB voltage on VBUS wakes system up from SYSTEM OFF.

[Przemek Ostrowski]

Thank you  Turbo J would you know if unplugging USB should also wake up MCU - assuming there is no bouncing on VBUS?

[Vidar Berg]

Yes, unplugging the USB will also trigger a wake up event.