Wake on VBUS connected but not disconnectedW

[Constantin]

Hi,

we are developing a device which should go to system off on receival of a command either via USB or BLE. If the device is connected via USB and is put into sleep it wakes up if the cable is disconnected. But it should stay in system off. Any idea why this happens and how to avoid it.

Kind regards,

C.W.

[Constantin]

Do you have any hint regarding my last comment?

[Constantin]

Ah this makes sense. Because it happens when  I unplug the cable. But I would assume that the normal procedure should be reverse. The MCU should switch on when the cable is plugged in. Is there a way to configure this for the VBUS sensing? Kind regards,

C.W.

[Vidar Berg]

The VBUS detect mechanism is hardwired and not configurable. I also see the same behavior as you now when test this on a dev kit. That is, the device wakes up from System OFF both when the cable is inserted and removed.

Maybe you can use the APP_USBD_EVT_POWER_DETECTED event in combination with the RESETREAS VBUS bit read on startup to determine if you want to return to System OFF or not?