What is the equivalent of S110's enum "NRF_CLOCK_LFCLKSRCS" in S140?

RE: What is the equivalent of S110's enum "NRF_CLOCK_LFCLKSRCS" in S140?

Jørn — Tue, 13 Jun 2017 10:53:00 GMT

The enum in SDK10 was two-fold. It set the clock source, and if a crystal was used defined the accuracy of it, if the RC was used it set the calibration time.

In SDK13 it is no longer just an enum, but a struct called nrf_clock_lf_cfg_t where you set the different fields related to LFCLK configuration. If the source is a crystal oscillator you must also set the xtal_accuracy field, which is one of the entries of the XTAL_ACCURACY defines. If the RC oscillator is used the accuracy is always 250ppm (Normal mode) and the calibration time is now set with the rc_ctiv and rc_temp_ctiv fields.

As your switch-case is concerned with the accuracy of the crystal, it should refer to the above mentioned defines if a crystal is used.

RE: What is the equivalent of S110's enum "NRF_CLOCK_LFCLKSRCS" in S140?

Mitch996 — Tue, 13 Jun 2017 10:22:44 GMT

Yes Yoern, I have found that, but I'm not exactly sure that they are same in nature, since the name doesn't suggest so. One appears to emphasize on source, another, accuracy.

Can they be used interchangeably?

RE: What is the equivalent of S110's enum "NRF_CLOCK_LFCLKSRCS" in S140?

Jørn — Tue, 13 Jun 2017 09:29:18 GMT

Hello Mitch996

You can find a similar enum for the LF clock source in the nrf_sdm.h (Softdevice manager).

As for clock source you have a few choices, crystal oscillator with external crystal, internal RC oscillator (normal and ultra-low power mode), synthesized from the HFCLK, and external clock source. See table 17, page 144 of the nRF52840 product specification.

Best regards

Jørn Frøysa