detect brownout on reset

[Dominik]

I would like to detect if a reset happened due to a brownout or an actual power off.

I tired so far using the GPREGRET and RESETREAS registers. They are useful to detect soft resets and distinguish between their causes, but since they are cleared on hard reset and brownout, they are not useful for this case. I tried using the POFCON together with the POWER FAILURE WARNING, which, even on the 2.7V threshold, only gives me about 40 ms to act. But in this time I can't write to pstorage, which takes much longer than that for a write cycle. So I can't store the impending brownout in persistent memory either.

So is there any other way in which I could detect a brownout after a reset?

I am using an NRF51822 with Softdevice s130 v1, and SDK 8.1

Any idea would be appreciated, thanks in advance Dominik

[Stefan Birnir Sverrisson]

Hi Dominik

Both answers on this thread might have ideas. Additionally, you could use internal ADC to monitor battery voltage and trigger flash operation in time. Some ADC examples here. There is also adc example in the SDK.

I don't otherwise see a way to know if reset was caused by brownout-reset or power-on-reset.

[Dominik]

Thanks for your input. Unfortunately using ADC to monitor the power doesn't work out, our device is connected to the 230V power line, not to a battery. But I think I found a nice solution. I use the power fail comparator, and in case of a warning, I set a brownout flag on the gpregret and force a softdevice reset, before the device actually brownsout. like this I also don't lose the gpregret register and can use the info after the reset.

[rgrr2]

Although this is old... how can one do a softdevice reset without actually resetting the device?