RE: Frequency shift with RTC on nRF52832

d.altmann — Sat, 11 May 2019 15:47:23 GMT

Hi,

Thank you for your response. And sorry for my long time message.

I have effectively change the capacitor and the quartz works little fine. I have 1 seconds of delay for each day passed.

(It's better than 10 seconds by day).

But in fact, when we compute the delay for a 20 ppm Crystal, we find a delay of 0.127 seconds by day.

It exist another function or peripheral to improve and reduce this delay ??

Thank you,

Best regards.

Damien ALTMANN

RE: Frequency shift with RTC on nRF52832

Sigurd — Thu, 02 May 2019 07:17:31 GMT

Hi,

To achieve correct oscillation frequency, the load capacitance must match the specification in the crystal data sheet. So the first thing to check is that you have reasonable load capacitance values for C11 and C12. General rule of thumb is to use C11 = C12 = 2*CL - 4 pF, where CL is the load capacitance of the crystal you are using (found in the crystal datasheet), and that C_pcb + C_pin is approximately 4 pF.
You might also find this repo useful. Also note that the SoftDevice uses RTC0, and app_timer uses RTC1.