1.5.21 Real-Time Counter (RTC)

Using The Library

The peripheral library provides polling and callback methods to indicate compare match or timer overflow.

• With polling, the application will need to continuously poll to check if the compare match has occurred or timer has overflowed

• With callback, the registered callback function will be called when the compare match occurs or timer overflows (Application do not have to poll continuously)

Callback method

This example demonstrates how to use RTC to generate periodic callback using clear on compare feature.

/* This function is called after period expires */
void Timeout_Handler(RTC_TIMER32_INT_MASK intCause, uintptr_t context)
{
    if((intCause & RTC_TIMER32_INT_MASK_CMP0) == RTC_TIMER32_INT_MASK_CMP0)
    {
        LED_Toggle();
    }
}

int main(void)
{
    /* Initialize all modules */
    SYS_Initialize ( NULL );
    RTC_Timer32CallbackRegister(Timeout_Handler,0);
    RTC_Timer32InterruptEnable(RTC_TIMER32_INT_MASK_CMP0);
    RTC_Timer32Start();
}

Library Interface

Real-Time Counter peripheral library provides the following interfaces:

Functions

Data types and constants

16-bit timer mode(Mode 1)

The RTC counter in 16-bit timer mode will increment until it matches with 16-bit period value, and then wrap to 0x0000. This sets the the overflow interrupt. The counter value is continuously compared with two 32-bit Compare registers (Compare 0, Compare 1), and sets the respective compare match interrupt when compare match occurs. The RTC timer has 10-bit programmable prescaler, it can generate periodic events on the upper eight bits of the RTC prescaler. The resulting periodic frequency is from 1Hz to 128 Hz depending on the selected prescaler bit position to generate periodic interrupt.

Using The Library

The peripheral library provides polling and callback methods to indicate compare match or period expiry.

• With polling, the application will need to continuously poll to check if the compare match has occurred or counter has overflowed.

• With callback, the registered callback function will be called when the period match or compare match occurs(his means the application do not have to poll continuously)

Callback method This example demonstrates how to use RTC to generate periodic callback.

/* This function is called after period expires */
void RTC_Callback(RTC_TIMER16_INT_MASK interruptCause, uintptr_t context)
{

    if(interruptCause &  RTC_TIMER16_INT_MASK_PERIOD_MATCH)
    {
        // The period has matched.
        LED_Toggle();
    }

}

int main(void)
{

    /* Register callback function for RTC */
    RTC_Timer16CallbackRegister(RTC_Callback, (uintptr_t)NULL);

    /* Enable Period Interrupt */
    RTC_Timer16InterruptEnable( RTC_TIMER16_INT_MASK_PERIOD_MATCH);

    /* Start RTC Timer */
    RTC_Timer16Start();
}

Functions

Data types and constants

Clock and Calendar (Mode 2)

The RTC provides a full binary-coded decimal (BCD) clock that includes century (19/20), year (with leap years), month, day,hours, minutes, and seconds. The RTC can operate in 24-hour mode or in 12-hour mode with an AM/PM indicator. The RTC continues to run in the device's low-power sleep modes, to track the current time and date information. The RTC can be used as a source to wake up the system at a scheduled time or periodically using the alarm functions.

Using The Library

The RTC keeps track of the current time and generates an alarm at the desired time. The RTC Alarm has six programmable fields: year, month, date, hours, minutes, and seconds. The alarm mask allows following options to generate alarm.

• Alarm mask to compare seconds field (SS) - Generates alarm once per minute

• Alarm mask to compare minutes and seconds field (MMSS) - Generates alarm once per hour

• Alarm mask to compare hours, minutes and seconds field (HHMMSS) - Generates alarm once per day

• Alarm mask to compare date, hours, minutes, and seconds field (DDHHMMSS) - Generates alarm once per month

• Alarm mask to compare month, date, hours, minutes and seconds (MMDDHHMMSS) - Generates alarm once per year

• Alarm mask to compare year, month, date, hours, minutes and seconds (YYMMDDHHMMSS) - Generates alarm on exact day and time

This example demonstrates how to set the RTC time, and alarm time to generate an alarm interrupt at the desired time of the day.

bool alarm_triggered;

void RTC_Callback(RTC_CLOCK_INT_MASK int_cause , uintptr_t  context)
{
    if (int_cause & RTC_CLOCK_INT_MASK_ALARM)
    {
        alarm_triggered = true;
        LED_Toggle();
    }
}

int main ( void )
{
    /* Initialize System Time and Alarm Time */
    struct tm sys_time;
    struct tm alarm_time;

    /* Register Callback */
    RTC_CallbackRegister(RTC_Callback, (uintptr_t) NULL);


    /* Set Time and date
      15-01-2018 12:00:00 Monday */
    sys_time.tm_hour = 12;      /* hour [0,23] */
    sys_time.tm_sec = 00;       /* seconds [0,61] */
    sys_time.tm_min = 00;       /* minutes [0,59] */
    sys_time.tm_mon = 0;        /* month of year [0,11] */
    sys_time.tm_year = 118;     /* years since 1900 */
    sys_time.tm_mday = 15;      /* day of month [1,31] */
    sys_time.tm_wday = 1;       /* day of week [0,6] (Sunday = 0) */
                                /* tm_yday - day of year [0,365] */
                                /* tm_isdst - daylight savings flag */

    RTC_TimeSet(&sys_time);


    /* Set Alarm Time and date. Generate alarm every day when Hour, Minute and Seconds match.
       15-01-2018 12:00:20 Monday */
    alarm_time.tm_hour = 12;
    alarm_time.tm_sec = 20;
    alarm_time.tm_min = 00;
    alarm_time.tm_mon = 0;
    alarm_time.tm_year = 118;
    alarm_time.tm_mday = 15;
    alarm_time.tm_wday = 1;

    RTC_RTCCAlarmSet(&alarm_time, RTC_ALARM_MASK_HHMMSS);


    while ( true )
    {
        if(alarm_triggered == true)
        {
            printf("\n\rAlarm Triggered !!!!!!!!\n\r");
            alarm_triggered = false;
        }
    }

}

Functions

Data types and constants