Our application includes a 32.768 kHz crystal oscillator with a nominal +/- 20 PPM accuracy. When I factor in aging over 10 years and worst case variation due to temperature it could theoretically get to -250 PPM.
There are a variety of enumerated NRF_CLOCK_LFCLKSRC_XTAL_x_PPM initializers, and I'm not sure if I am best served by a nominal 20 PPM, a more typical 150 PPM, or a pessimistic 250 PPM initializer.
How is the specified PPM accuracy used by the softdevice, and what would be the correct choice in this situation?
Thanks and Best Regards, Matt