Change Clock Source NRF52832 app beacon example

RE: Change Clock Source NRF52832 app beacon example

Susheel Nuguru — Tue, 09 Aug 2016 11:51:31 GMT

.xtal_accuracy is ignored for RC. you can set it to 0.

RE: Change Clock Source NRF52832 app beacon example

Luke — Wed, 27 Jul 2016 15:00:40 GMT

Thanks, now it works!! The configuration I chose:

#define NRF_CLOCK_LFCLKSRC      {.source        = NRF_CLOCK_LF_SRC_RC,            \
                             .rc_ctiv       = 16,                                \
                             .rc_temp_ctiv  = 2,                                \
                             .xtal_accuracy = NRF_CLOCK_LF_XTAL_ACCURACY_20_PPM}

RE: Change Clock Source NRF52832 app beacon example

Ole Bauck — Wed, 27 Jul 2016 07:51:24 GMT

Hi Luke

You have to set the calibration interval rc_ctiv if you are using NRF_CLOCK_LF_SRC_RC. See the documentation for the nrf_clock_lf_cfg_t struct. As it says:

uint8_t nrf_clock_lf_cfg_t::rc_ctiv

Only for NRF_CLOCK_LF_SRC_RC: Calibration timer interval in 1/4 second units (nRF51: 1-64, nRF52: 1-32).

And for nRF52 specifically:

For nRF52, the application must ensure calibration at least once every 8 seconds to ensure +/-250ppm clock stability. The recommended configuration for NRF_CLOCK_LF_SRC_RC on nRF52 is rc_ctiv=16 and rc_temp_ctiv=2. This will ensure calibration at least once every 8 seconds and for temperature changes of 0.5 degrees Celsius every 4 seconds. See the Product Specification for the nRF52 device being used for more information.