Can I maintain a timer active during off (sleep) state in nRF51822?

[Lucast85]

Hi all,

I'm using the nRF51822-EK (PCA10001) and I'm going to develop a bluetooth cadence (and speed) sensor for MTBs. I desire low power consumption and i though to put the nRF in "system off mode" during inactivity time. The nRF51822 woke up by an analog signal (sensed by LPCOMP) whenever the bicycle's wheel perform an entire revolution. So, I must measure time between two consecutive wheel's revolution. It's possible to have a timer active during the "system off mode" ?

Thank you all!!!

[Nikita]

You can't use it in system off.

But you can use RTC in system on low power mode. In this mode it'll consume around 3uA = ION + IRTC + IX32k.

[Petter Myhre]

Nikita is correct, also see this for more information. Just for clarification, Low Power mode is a sub power mode of System ON mode.

[Petter Myhre]

For clarification, the nRF51 Series has two power modes; System ON and System OFF. In System OFF the CPU is always sleeping, while in System ON it may be sleeping.