Functions and data related to the low-frequency clock. More...

#include <nrfcxx/clock.hpp>

Static Public Member Functions
static bool	active ()
	Return `true` iff the low-frequency clock is active.

static int	configure (int on)
	Enable, disable, or query the state of the low-frequency clock. More...

static uint32_t	source ()
	Return the actual source for the low-frequency clock.

static int	source_configure (int src, unsigned cal_interval_qs=DefaultRCOCalInterval_qs)
	Enable, disable, or query the source of the low-frequency crystal. More...

Static Public Attributes
constexpr static unsigned int	Frequency_Hz = 32768U
	The low-frequency clock always runs at nominal 32 KiHz.

constexpr static unsigned int	DefaultRCOCalInterval_qs = 4 * 4
	The default RC oscillator calibration interval, in quarter-seconds. More...

Detailed Description

Functions and data related to the low-frequency clock.

The low-frequency clock must be explicitly enabled and may be sourced from a crystal oscillator, an RC oscillator, or synthesized from the high frequency crystal.

Note: This is a data type for visibility management only; all members are static and it is not possible to create or manipulate instances of the type.

Member Function Documentation

◆ configure()

static int nrfcxx::clock::lfclk::configure ( int on )

static

Enable, disable, or query the state of the low-frequency clock.

Parameters

on	a positive value to enable the clock; zero to disable it; a negative value to return the configured state without change.

Returns: A positive if the clock was configured on prior to this call, zero if the clock was configured off, a negative value if a configuration change could not be executed.

Note: The default state of the clock on power-up is disabled, but initialize() will always enable it.; source_configure() may be used to select the desired clock source, but it will not take effect until the next time the clock changes from disabled to enabled.; This function will fail if calibration is being performed when disabling LFCLK sourced from #CLOCK_LFCLKSRC_SRC_RC. Retry after about 16 ms.

◆ source_configure()

static int nrfcxx::clock::lfclk::source_configure	(	int	src,
		unsigned	cal_interval_qs = `DefaultRCOCalInterval_qs`
	)

static

Enable, disable, or query the source of the low-frequency crystal.

Parameters

src	one of #CLOCK_LFCLKSRC_SRC_RC, #CLOCK_LFCLKSRC_SRC_Xtal, or #CLOCK_LFCLKSRC_SRC_Synth, or a negative value to return the configured source without change.
cal_interval_qs	the clock calibration interval when configured to use #CLOCK_LFCLKSRC_SRC_RC. Pass zero to disable repeated calibration. Ignored for other configuration options.

Returns: one of #CLOCK_LFCLKSRC_SRC_RC, #CLOCK_LFCLKSRC_SRC_Xtal, or #CLOCK_LFCLKSRC_SRC_Synth, or a negative value on an attempt to change the clock source while active() is true.

Note: The power-up default source is #CLOCK_LFCLKSRC_SRC_RC, but clock::initialize() may change that to a crystal if the board provides one.; Although passing zero disables repeated calibration when src is #CLOCK_LFCLKSRC_SRC_RC the system will unconditionally execute one calibration as soon as the clock has started with this source.

Field Documentation

◆ DefaultRCOCalInterval_qs

constexpr static unsigned int nrfcxx::clock::lfclk::DefaultRCOCalInterval_qs = 4 * 4

staticconstexpr

The default RC oscillator calibration interval, in quarter-seconds.

A 4 s interval is expected to maintain 250 ppm accuracy in varying temperature environments.

The documentation for this class was generated from the following file:

nrfcxx/clock.hpp