Problem identifying which GPIO is the cause for waking the MCU out of "system off" mode

RE: Problem identifying which GPIO is the cause for waking the MCU out of "system off" mode

snoopy20 — Fri, 27 Dec 2024 12:58:39 GMT

I would say so as well. I've not had to deal with that errata.

The wonderful thing about the NRF52 series is there's always a workaround. Can you live with it for debug mode? Assuming not...

Both pins are going to pull low but there'll be a slight timing difference which you can use.

Complete hardware based solution...

Wire both pins to GPIOTE.

Then pass those events to two PPI's each wired into a separate PPI_GRP. Use the Fork on each PPI to disable the opposite group.

Now also wire each PPI to the EGU using different event channels. Enable the interrupt.

Now you'll get one interrupt and can look at the EGU events to know which pin actually fired.

Reset the GPIO configs to deal with the errata, clear the PPI events and enable both PPI groups to start over.

RE: Problem identifying which GPIO is the cause for waking the MCU out of "system off" mode

Kenneth — Fri, 27 Dec 2024 11:51:34 GMT

Kenneth

RE: Problem identifying which GPIO is the cause for waking the MCU out of "system off" mode

Tsahi Holand — Wed, 25 Dec 2024 10:06:01 GMT

Thank you Andrew for your reply.

I seem to have found the cause of the problem although I have no idea why this happens:

Please consider the following sequence of events:

- 2 GPIOs (P0.11 and P0.26) are configured as pullup

- 2 GPIOs (P0.11 and P0.26) are configured to sense low

- 2 GPIOs (P0.11 and P0.26) latch is cleared

- sd_power_system_off() is called

- After 10 seconds the P0.26 pin is pulled low by an external RTC (latch is triggered)

- For some reason P0.11 is also pulled low and so latch is also triggered

This happens only if the J-link RTT viewer is connected ?!

When the viewer is disconnected the GPIOs behave as expected:

Maybe you can shed some light?

Thanks,

Tsahi

RE: Problem identifying which GPIO is the cause for waking the MCU out of "system off" mode

snoopy20 — Tue, 24 Dec 2024 16:31:31 GMT

It's not floating, it's a weak high. The weak pullup configuration is reset upon system reset and then it's floating.

Ensure you're disabling the input buffer for all pins you don't need it on.

Ensure the NFC pins are disabled if you are intending to use those pins as GPIO. I can't recall which two pins they are but think they are 12 and 13 (I use 810 which doesn't have them).

Ensure you are setting the state of the pin (pull-up high) before enabling sense, not as one statement which is the obvious way to do it, otherwise they may race (sense fires before pull-up has enabled or pulled the pin high if there's some capacitance on it etc).

With these actions done then if behaviour still isn't correct

Take at the RESETREA to see why the CPU is resetting, if that's still an issue.
Take a look at the LATCH values in GPIO to see which ones are firing.

Regards,

Andrew