Hello everyone,
I am currently developing a custom application on a DMW1001-Dev board.
I need to keep track of time for a synchronization between multiple devices.
I checked on Nordic forums and I implemented a RTC counter for this (depending on the 32.768KHz xtal), following all their recommendations to get the best precision. However, I am now blocked with a 100-120ppm precision that I don’t understand…
I checked the Schematics of the DWM1001 and I confirmed that it uses a 32K crystal (Commutek). I tryed to find this KCBB crystal (as specified in the BOM) and I found this one : TF-SMD (http://www.commutek.com/?p=6&cat2=2&id=30&s=&lang=en).
My problem is that this xtal seems to need a capacitance load of 12.5pF whereas the nrf52832 has a 9pF reference for the 2 capacitors of 12pF on the PCB.
Is it possible that the capacitors needed by DWM1001 modules for getting a +/-10ppm precision has wrong value, 12pF instead of 21pF maybe ? Is it that the xtal that I found is not the right one. Have someone any other idea which could cause the drift of my RTC ?
I hope you will give me some insights, thanks, Fabien.