Wake on VBUS connected but not disconnectedW

RE: Wake on VBUS connected but not disconnectedW

Constantin — Thu, 14 Jul 2022 08:37:34 GMT

Okay, it can be only fixed if I read the reset reason and usb state upon start from reset and check it was a cable remove or cable plugin. In case of a cable remove it returns to sleep. This seems to be the only solution so far.

RE: Wake on VBUS connected but not disconnectedW

Vidar Berg — Fri, 24 Jun 2022 11:05:35 GMT

It's strange that it does not wake up when you insert the cable. I was not able to replicate it here. I just took the peripheral blinky example and added this line to it:

Maybe you can try the same to help narrow down the problem?

Thanks,

RE: Wake on VBUS connected but not disconnectedW

Constantin — Fri, 24 Jun 2022 09:46:31 GMT

Okay, but how do I read the APP_USBD_EVT_POWER_DETECTED on start. And the main issue is that it does not switch on when I plug in the cable only when I remove. I guess that is the main issue I need to solve. Because I would guess that both make a VBUS event but only the one produces a reset.

RE: Wake on VBUS connected but not disconnectedW

Vidar Berg — Fri, 24 Jun 2022 07:52:28 GMT

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?

RE: Wake on VBUS connected but not disconnectedW

Constantin — Thu, 23 Jun 2022 18:52:55 GMT

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.

RE: Wake on VBUS connected but not disconnectedW

Vidar Berg — Thu, 23 Jun 2022 15:12:14 GMT

Bit 20 corresponds to VBUS:

RE: Wake on VBUS connected but not disconnectedW

Constantin — Thu, 23 Jun 2022 14:50:56 GMT

Okay but I would say that the code is correct

    // reset areas

    static uint32_ reset_reas = 0x00000000;
    sd_power_reset_reason_get(&reset_reas);
    sd_power_reset_reason_clr(0x000F000F);
    NRF_LOG_ERROR("Reset reason %x", reset_reas);

Because it behaves correct when I do a reset via the debugger. It gives 0x4 which means SREQ which is correct. But if I pull the USB cable it gives 0x100000. Which is protected.

RE: Wake on VBUS connected but not disconnectedW

Vidar Berg — Thu, 23 Jun 2022 12:46:01 GMT

I don't have any good explanations as to why the RESETREAS is set with an invalid bit. This only happens when you are clearing the bits from your app?

RE: Wake on VBUS connected but not disconnectedW

Constantin — Thu, 23 Jun 2022 09:22:44 GMT

Do you have any hint regarding my last comment?

RE: Wake on VBUS connected but not disconnectedW

Constantin — Wed, 22 Jun 2022 13:30:31 GMT

Okay with the clear it brought after pulling the cable: 0x100000 which does not make sense at all. Because it is not a reason for any reset.

RE: Wake on VBUS connected but not disconnectedW

Constantin — Wed, 22 Jun 2022 13:09:35 GMT

Hi Vidar,

I've double checked that I am not in DEBUG and I will check if the RESETREAS register is cleared after read. But I thought that `sd_power_reset_reason_get` is clearing the bits automatically.

Kind regards,

Constantin

RE: Wake on VBUS connected but not disconnectedW

Vidar Berg — Wed, 22 Jun 2022 13:00:20 GMT

Hi,

Did you make sure the device was not in Debug Interface mode before you entered System OFF mode? The device will only enter Emulated System OFF mode if not. Also, please note that the RESETREAS register is retained so bits should be cleared after they are read. From your current readout it is not possible to tell if the last reset source was a SREQ or DIF.

RE: Wake on VBUS connected but not disconnectedW

Constantin — Tue, 21 Jun 2022 16:06:29 GMT

When analyzing the RESETREAS register after wakeup the following can be found

SREQ

Reset from soft reset detected

NotDetected

Not detected

Detected

and

DIF

Reset due to wake up from System OFF mode when wakeup is triggered from entering into debug interface mode

NotDetected

Not detected

Detected

I am not sure what it means and appreciate any help.

Kind regards, C.W.