Useage of HFCLK at SD110 startup

RE: Useage of HFCLK at SD110 startup

butch — Wed, 28 Dec 2016 14:26:25 GMT

The nRF52 product spec under Clock/Electrical specifications does give the typical startup current and a typical startup time for the HFXO.

RE: Useage of HFCLK at SD110 startup

butch — Wed, 28 Dec 2016 14:21:07 GMT

An old thread but ... the answer describes the 32kHz clock while the question was about the 16MHz clock. The radio needs the accurate 16MHz crystal clock. It does take about 0.5mSec to start (another thread says the SoftDevice starts it 1.5mSec before it is needed.) Which is less than the 20mSec reported in the original question. Another thread says the clock draws 25uA in standby, and 470uA when active (used by the radio.) The other thread doesn't say how much current the clock uses while starting (the active current?) You need these numbers to calculate a theoretical power budget, for the state: coming out of sleep and starting the HF clock so the radio can use it. As Stefan said, you can sleep the mcu during this state (because there is an interrupt on HFCLKSTARTED event.) You could read code to see whether SoftDevice sleeps, or spins the mcu (drawing 4mA) during this state?

RE: Useage of HFCLK at SD110 startup

Stefan Birnir Sverrisson — Tue, 25 Nov 2014 12:39:10 GMT

The softdevice itself should not take much time to enable. It can be however time consuming to enable the low frequency 32kHz external crystal clock source. When initializing the softdevice, you specify the 32kHz clock source to be either external crystal or the internal RC. Try to use the RC instead of the crystal in order to decrease the softdevice initialization time. If you want to use an external 32kHz crystal, you could start with manually enabling the crystal and go to sleep while you wait for it to start. Then you wake up again and initialize the softdevice.