Differentiating between brown-out vs initial power-up

[Chris]

Hi,

I am using the nrf51822 in an intermittent high-current application where if the battery is close to dead, will sometimes cause the chip to reset because the voltage is dropping below ~1.7V. The battery recovers and the chip starts running again.

Is it possible to determine whether a reset is caused by low voltage versus a complete battery change? I believe that RESETREAS will equal 0 in either case.

Any easy way to do this?

Thanks.

[Alex]

While nobody comment on it offering on-chip solution which I think doesn't exist, although I may be wrong, I would offer solution with external components. Simple voltage monitor with reference voltage 0-1.7V, lets say 1.2V and timed output with the timer longer than nRF chip internal reset. I think few hundred ms will be enough, need to double check. Then connect output to GPIO. With output active low if nRF on startup recognize zero that means battery was removed, if 1 then was voltage drop considering lowest battery drop not lower than 1.2V