Overview

The MCUXpresso SDK provides a driver for the Real Time Clock (RTC) of MCUXpresso SDK devices.

Function groups

The RTC driver supports operating the module as a time counter.

Initialization and deinitialization

The function RTC_Init() initializes the RTC with specified configurations. The function RTC_GetDefaultConfig() gets the default configurations.

The function RTC_Deinit() disables the RTC timer and disables the module clock.

Set & Get Datetime

The function RTC_SetDatetime() sets the timer period in seconds. Users pass in the details in date & time format by using the below data structure.

typedef struct _rtc_datetime
{
    uint16_t year;  
    uint8_t month;  
    uint8_t day;    
    uint8_t hour;   
    uint8_t minute; 
    uint8_t second; 
} rtc_datetime_t;

The function RTC_GetDatetime() reads the current timer value in seconds, converts it to date & time format and stores it into a datetime structure passed in by the user.

Set & Get Alarm

The function RTC_SetAlarm() sets the alarm time period in seconds. Users pass in the details in date & time format by using the datetime data structure.

The function RTC_GetAlarm() reads the alarm time in seconds, converts it to date & time format and stores it into a datetime structure passed in by the user.

Start & Stop timer

The function RTC_StartTimer() starts the RTC time counter.

The function RTC_StopTimer() stops the RTC time counter.

Status

Provides functions to get and clear the RTC status.

Interrupt

Provides functions to enable/disable RTC interrupts and get current enabled interrupts.

RTC Oscillator

Some SoC's allow control of the RTC oscillator through the RTC module.

The function RTC_SetOscCapLoad() allows the user to modify the capacitor load configuration of the RTC oscillator.

Monotonic Counter

Some SoC's have a 64-bit Monotonic counter available in the RTC module.

The function RTC_SetMonotonicCounter() writes a 64-bit to the counter.

The function RTC_GetMonotonicCounter() reads the monotonic counter and returns the 64-bit counter value to the user.

The function RTC_IncrementMonotonicCounter() increments the Monotonic Counter by one.

Typical use case

RTC tick example

Example to set the RTC current time and trigger an alarm.

int main(void)
{
    uint32_t sec;
    uint32_t currSeconds;
    rtc_datetime_t date;
    rtc_config_t rtcConfig;
    /* Board pin, clock, debug console init */
    BOARD_InitHardware();
    /* Init RTC */
    RTC_GetDefaultConfig(&rtcConfig);
    RTC_Init(RTC, &rtcConfig);
    /* Select RTC clock source */
    BOARD_SetRtcClockSource();
    PRINTF("RTC example: set up time to wake up an alarm\r\n");
    /* Set a start date time and start RT */
    date.year = 2014U;
    date.month = 12U;
    date.day = 25U;
    date.hour = 19U;
    date.minute = 0;
    date.second = 0;
    /* RTC time counter has to be stopped before setting the date & time in the TSR register */
    RTC_StopTimer(RTC);
    /* Set RTC time to default */
    RTC_SetDatetime(RTC, &date);
    /* Enable RTC alarm interrupt */
    RTC_EnableInterrupts(RTC, kRTC_AlarmInterruptEnable);
    /* Enable at the NVIC */
    EnableIRQ(RTC_IRQn);
    /* Start the RTC time counter */
    RTC_StartTimer(RTC);
    /* This loop will set the RTC alarm */
    while (1)
    {
        busyWait = true;
        /* Get date time */
        RTC_GetDatetime(RTC, &date);
        /* print default time */
        PRINTF("Current datetime: %04hd-%02hd-%02hd %02hd:%02hd:%02hd\r\n", date.year, date.month, date.day, date.hour,
               date.minute, date.second);
        /* Get alarm time from the user */
        sec = 0;
        PRINTF("Input the number of second to wait for alarm \r\n");
        PRINTF("The second must be positive value\r\n");
        while (sec < 1)
        {
            SCANF("%d", &sec);
        }
        /* Read the RTC seconds register to get current time in seconds */
        currSeconds = RTC->TSR;
        /* Add alarm seconds to current time */
        currSeconds += sec;
        /* Set alarm time in seconds */
        RTC->TAR = currSeconds;
        /* Get alarm time */
        RTC_GetAlarm(RTC, &date);
        /* Print alarm time */
        PRINTF("Alarm will occur at: %04hd-%02hd-%02hd %02hd:%02hd:%02hd\r\n", date.year, date.month, date.day,
               date.hour, date.minute, date.second);
        /* Wait until alarm occurs */
        while (busyWait)
        {
        }
        PRINTF("\r\n Alarm occurs !!!! ");
    }
}

Data Structures
struct	rtc_datetime_t
	Structure is used to hold the date and time. More...

struct	rtc_config_t
	RTC config structure. More...

Enumerations
enum	rtc_interrupt_enable_t { kRTC_TimeInvalidInterruptEnable = RTC_IER_TIIE_MASK, kRTC_TimeOverflowInterruptEnable = RTC_IER_TOIE_MASK, kRTC_AlarmInterruptEnable = RTC_IER_TAIE_MASK, kRTC_SecondsInterruptEnable = RTC_IER_TSIE_MASK }
	List of RTC interrupts. More...

enum	rtc_status_flags_t { kRTC_TimeInvalidFlag = RTC_SR_TIF_MASK, kRTC_TimeOverflowFlag = RTC_SR_TOF_MASK, kRTC_AlarmFlag = RTC_SR_TAF_MASK }
	List of RTC flags. More...

enum	rtc_osc_cap_load_t { kRTC_Capacitor_2p = RTC_CR_SC2P_MASK, kRTC_Capacitor_4p = RTC_CR_SC4P_MASK, kRTC_Capacitor_8p = RTC_CR_SC8P_MASK, kRTC_Capacitor_16p = RTC_CR_SC16P_MASK }
	List of RTC Oscillator capacitor load settings. More...

Functions
static void	RTC_SetOscCapLoad (RTC_Type *base, uint32_t capLoad)
	This function sets the specified capacitor configuration for the RTC oscillator. More...

static void	RTC_Reset (RTC_Type *base)
	Performs a software reset on the RTC module. More...

Driver version
#define	FSL_RTC_DRIVER_VERSION (MAKE_VERSION(2, 0, 0))
	Version 2.0.0.

Initialization and deinitialization
void	RTC_Init (RTC_Type base, const rtc_config_t config)
	Ungates the RTC clock and configures the peripheral for basic operation. More...

static void	RTC_Deinit (RTC_Type *base)
	Stops the timer and gate the RTC clock. More...

void	RTC_GetDefaultConfig (rtc_config_t *config)
	Fills in the RTC config struct with the default settings. More...

Current Time & Alarm
status_t	RTC_SetDatetime (RTC_Type base, const rtc_datetime_t datetime)
	Sets the RTC date and time according to the given time structure. More...

void	RTC_GetDatetime (RTC_Type base, rtc_datetime_t datetime)
	Gets the RTC time and stores it in the given time structure. More...

status_t	RTC_SetAlarm (RTC_Type base, const rtc_datetime_t alarmTime)
	Sets the RTC alarm time. More...

void	RTC_GetAlarm (RTC_Type base, rtc_datetime_t datetime)
	Returns the RTC alarm time. More...

Interrupt Interface
static void	RTC_EnableInterrupts (RTC_Type *base, uint32_t mask)
	Enables the selected RTC interrupts. More...

static void	RTC_DisableInterrupts (RTC_Type *base, uint32_t mask)
	Disables the selected RTC interrupts. More...

static uint32_t	RTC_GetEnabledInterrupts (RTC_Type *base)
	Gets the enabled RTC interrupts. More...

Status Interface
static uint32_t	RTC_GetStatusFlags (RTC_Type *base)
	Gets the RTC status flags. More...

void	RTC_ClearStatusFlags (RTC_Type *base, uint32_t mask)
	Clears the RTC status flags. More...

Timer Start and Stop
static void	RTC_StartTimer (RTC_Type *base)
	Starts the RTC time counter. More...

static void	RTC_StopTimer (RTC_Type *base)
	Stops the RTC time counter. More...

Data Structure Documentation

struct rtc_datetime_t

Data Fields
uint16_t	year
	Range from 1970 to 2099. More...

uint8_t	month
	Range from 1 to 12. More...

uint8_t	day
	Range from 1 to 31 (depending on month). More...

uint8_t	hour
	Range from 0 to 23. More...

uint8_t	minute
	Range from 0 to 59. More...

uint8_t	second
	Range from 0 to 59. More...

Field Documentation

uint16_t rtc_datetime_t::year

uint8_t rtc_datetime_t::month

uint8_t rtc_datetime_t::day

uint8_t rtc_datetime_t::hour

uint8_t rtc_datetime_t::minute

uint8_t rtc_datetime_t::second

struct rtc_config_t

This structure holds the configuration settings for the RTC peripheral. To initialize this structure to reasonable defaults, call the RTC_GetDefaultConfig() function and pass a pointer to your config structure instance.

The config struct can be made const so it resides in flash

Data Fields
bool	wakeupSelect
	true: Wakeup pin outputs the 32 KHz clock; false:Wakeup pin used to wakeup the chip

bool	updateMode
	true: Registers can be written even when locked under certain conditions, false: No writes allowed when registers are locked

bool	supervisorAccess
	true: Non-supervisor accesses are allowed; false: Non-supervisor accesses are not supported

uint32_t	compensationInterval
	Compensation interval that is written to the CIR field in RTC TCR Register.

uint32_t	compensationTime
	Compensation time that is written to the TCR field in RTC TCR Register.

Enumeration Type Documentation

enum rtc_interrupt_enable_t

Enumerator
kRTC_TimeInvalidInterruptEnable	Time invalid interrupt.
kRTC_TimeOverflowInterruptEnable	Time overflow interrupt.
kRTC_AlarmInterruptEnable	Alarm interrupt.
kRTC_SecondsInterruptEnable	Seconds interrupt.

enum rtc_status_flags_t

Enumerator
kRTC_TimeInvalidFlag	Time invalid flag.
kRTC_TimeOverflowFlag	Time overflow flag.
kRTC_AlarmFlag	Alarm flag.

enum rtc_osc_cap_load_t

Enumerator
kRTC_Capacitor_2p	2 pF capacitor load
kRTC_Capacitor_4p	4 pF capacitor load
kRTC_Capacitor_8p	8 pF capacitor load
kRTC_Capacitor_16p	16 pF capacitor load

Function Documentation

void RTC_Init	(	RTC_Type *	base,
		const rtc_config_t *	config
	)

This function issues a software reset if the timer invalid flag is set.

Note: This API should be called at the beginning of the application using the RTC driver.

Parameters

base	RTC peripheral base address
config	Pointer to the user's RTC configuration structure.

static void RTC_Deinit ( RTC_Type * base )

inlinestatic

Parameters

base	RTC peripheral base address

void RTC_GetDefaultConfig ( rtc_config_t * config )

The default values are as follows.

*    config->wakeupSelect = false;
*    config->updateMode = false;
*    config->supervisorAccess = false;
*    config->compensationInterval = 0;
*    config->compensationTime = 0;
* 

Parameters

config Pointer to the user's RTC configuration structure.

status_t RTC_SetDatetime	(	RTC_Type *	base,
		const rtc_datetime_t *	datetime
	)

The RTC counter must be stopped prior to calling this function because writes to the RTC seconds register fail if the RTC counter is running.

Parameters

base	RTC peripheral base address
datetime	Pointer to the structure where the date and time details are stored.

Returns: kStatus_Success: Success in setting the time and starting the RTC kStatus_InvalidArgument: Error because the datetime format is incorrect

void RTC_GetDatetime	(	RTC_Type *	base,
		rtc_datetime_t *	datetime
	)

Parameters

base	RTC peripheral base address
datetime	Pointer to the structure where the date and time details are stored.

status_t RTC_SetAlarm	(	RTC_Type *	base,
		const rtc_datetime_t *	alarmTime
	)

The function checks whether the specified alarm time is greater than the present time. If not, the function does not set the alarm and returns an error.

Parameters

base	RTC peripheral base address
alarmTime	Pointer to the structure where the alarm time is stored.

Returns: kStatus_Success: success in setting the RTC alarm kStatus_InvalidArgument: Error because the alarm datetime format is incorrect kStatus_Fail: Error because the alarm time has already passed

void RTC_GetAlarm	(	RTC_Type *	base,
		rtc_datetime_t *	datetime
	)

Parameters

base	RTC peripheral base address
datetime	Pointer to the structure where the alarm date and time details are stored.

static void RTC_EnableInterrupts	(	RTC_Type *	base,
		uint32_t	mask
	)

inlinestatic

Parameters

base	RTC peripheral base address
mask	The interrupts to enable. This is a logical OR of members of the enumeration rtc_interrupt_enable_t

static void RTC_DisableInterrupts	(	RTC_Type *	base,
		uint32_t	mask
	)

inlinestatic

Parameters

base	RTC peripheral base address
mask	The interrupts to enable. This is a logical OR of members of the enumeration rtc_interrupt_enable_t

static uint32_t RTC_GetEnabledInterrupts ( RTC_Type * base )

inlinestatic

Parameters

base	RTC peripheral base address

Returns: The enabled interrupts. This is the logical OR of members of the enumeration rtc_interrupt_enable_t

static uint32_t RTC_GetStatusFlags ( RTC_Type * base )

inlinestatic

Parameters

base	RTC peripheral base address

Returns: The status flags. This is the logical OR of members of the enumeration rtc_status_flags_t

void RTC_ClearStatusFlags	(	RTC_Type *	base,
		uint32_t	mask
	)

Parameters

base	RTC peripheral base address
mask	The status flags to clear. This is a logical OR of members of the enumeration rtc_status_flags_t

static void RTC_StartTimer ( RTC_Type * base )

inlinestatic

After calling this function, the timer counter increments once a second provided SR[TOF] or SR[TIF] are not set.

Parameters

base	RTC peripheral base address

static void RTC_StopTimer ( RTC_Type * base )

inlinestatic

RTC's seconds register can be written to only when the timer is stopped.

Parameters

base	RTC peripheral base address

static void RTC_SetOscCapLoad	(	RTC_Type *	base,
		uint32_t	capLoad
	)

inlinestatic

Parameters

base	RTC peripheral base address
capLoad	Oscillator loads to enable. This is a logical OR of members of the enumeration rtc_osc_cap_load_t

static void RTC_Reset ( RTC_Type * base )

inlinestatic

This resets all RTC registers except for the SWR bit and the RTC_WAR and RTC_RAR registers. The SWR bit is cleared by software explicitly clearing it.

Parameters

base	RTC peripheral base address

Overview

Function groups

Initialization and deinitialization

Set & Get Datetime

Set & Get Alarm

Start & Stop timer

Status

Interrupt

RTC Oscillator

Monotonic Counter

Typical use case

RTC tick example

Data Structures

Enumerations

Functions

Driver version

Initialization and deinitialization

Current Time & Alarm

Interrupt Interface

Status Interface

Timer Start and Stop

Data Structure Documentation

Data Fields

Field Documentation

Data Fields

Enumeration Type Documentation

Function Documentation