Wake-up time from System OFF to start advertising

[Mario Amigot]

Hello,

I have made some current and timing measurements on the nRF51822 Development Kit (connected to a nRFgo Starter Kit) running some of the example applications provided in the SDK (Power Profiling Application and Heart Rate application example), and I have noticed that there is a wake-up period of 350 msec consuming an average of 0.9 mA aprox. from System OFF mode to the start of advertising. Why is this period so long? How can it be reduced?

Thanks in advance

[Mario Amigot]

I mean, comparing nRF51822 to other BLE SoC chips in the market, I find this 350 msec period too long and power consuming, especially taking into account that nRF51822 doesn't need to mirror/get the code from an OTP memory. So my questions are: what is exactly the "sub-process" (some kind of calibration or trimming?) which slows down the wake-up process from System OFF to start advertising? Can this "sub-process" time be reduced somehow?

[Håkon Alseth]

Hi,

That's due to the external 32kHz startup (usually from 0.3 - 1 sec, depending on the xosc). Look at this thread on how to reduce this: devzone.nordicsemi.com/.../softdevice_handler_init-duration

BR Håkon