4.14.9 Real-Time Counter

This use-case configures the Real Time Counter (RTC) to generate an overflow interrupt at a period of 1s, which turns the LED on (assume active low). 100ms later the compare interrupt turns the LED off, resulting in a 100ms blink.

After configuring the components as described above, click 'Generate' to generate the code. Then add the following code snippets to your application:

void RTC_CMP_Callback(void){
    LED_SetHigh();}

void RTC_OVF_Callback(void){
    LED_SetLow();
}

int main(void)
{
    SYSTEM_Initialize();
    
    RTC_SetCMPIsrCallback(RTC_CMP_Callback);
    RTC_SetOVFIsrCallback(RTC_OVF_Callback);

    while(1)
    {
    }
}

Using the Event System a pulse is generated on a RTC compare match of 200 ms. The RTC is used to toggle on the RTC overflow every second, using interrupts.

After configuring the components as described above, click 'Generate' to generate the code. Then add the following code snippets to your application:

void RTC_OVF_Callback(void){
    LED_Toggle();
}

int main(void)
{
    SYSTEM_Initialize();
    
    RTC_SetOVFIsrCallback(RTC_OVF_Callback);

    while(1)
    {
    }
}

The Periodic Interrupt Timer (PIT) function of the RTC to wake up the CPU. Every second a PIT interrupt wakes the AVR from Power Down mode, then in the PIT callback a LED is toggled, before we put the CPU to sleep again.

NOTE: The EVSYSEVOUTx pin (Event System event out), will pulse on a RTC_CMP or RTC_OVF event, but will toggle on a PIT event.

After configuring the components as described above, click 'Generate' to generate the code. Then add the following code snippets to your application:

/* Required header files for RTC Use-case 2 */
#include "mcc_generated_files/system/system.h"
#include <avr/sleep.h>

int main(void)
{
    SYSTEM_Initialize();

    //RTC PIT ISR callback function
    RTC_SetPITIsrCallback(RTC_PIT_CallBack);
    while(1)
    {
        //Enter power down mode
        sleep_cpu();
    }    
}

We refactor the application, demonstrating how the Periodic Interrupt Timer works with the Event System. The same functionality, of a LED toggling every second is kept, without any code running.

NOTE: The EVSYSEVOUTx pin (Event System event out), will pulse on a RTC_CMP or RTC_OVF event, but will toggle on a PIT event.

/* Required header files for RTC Use-case 2 */
#include "mcc_generated_files/system/system.h"
#include <avr/sleep.h>

int main(void)
{
    SYSTEM_Initialize();

    while(1)
    {
        //Enter power down mode
        sleep_cpu();
    }
}

Set up the PIT to wake the MCU every 4s and set up the RTC Overflow interrupt to go back to sleep a second later. While awake use a delay to toggle the LED every 50ms.

After configuring the components as described above, click 'Generate' to generate the code. Then add the following code snippets to your application:

#include "mcc_generated_files/system/system.h"
#include <avr/sleep.h>
#include <util/delay.h>

volatile bool GOTOSLEEP = false;

void RTC_PIT_Callback(void){
    GOTOSLEEP = false;
}

void RTC_OVF_Callback(void)
{
    GOTOSLEEP = true;
}

int main(void)
{
    SYSTEM_Initialize();
    
    RTC_SetOVFIsrCallback(RTC_OVF_Callback);
    RTC_SetPITIsrCallback(RTC_PIT_Callback);

    while(1)
    {
        if (GOTOSLEEP) {
            LED_SetHigh();
            sleep_cpu();
            
            } else {
            LED_Toggle();
            _delay_ms(50);
        }
    }
}

• int8_t RTC_Initialize (void)

  Initialize RTC interface.

• void RTC_Start (void)

  API to start the counter register for RTC interface.

• void RTC_Stop (void)

  API to stop the counter register for RTC interface.

• void RTC_SetOVFIsrCallback (RTC_cb_t cb)

  Isr callback function to be called if overflow interrupt flag is set.

• void RTC_SetCMPIsrCallback (RTC_cb_t cb)

  Isr callback function to be called if Compare match interrupt flag is set.

• void RTC_SetPITIsrCallback (RTC_cb_t cb)

  Isr callback function to be called if PIT interrupt flag is set.

• ISR (RTC_CNT_vect)

• ISR (RTC_PIT_vect)

• void RTC_WriteCounter (uint16_t timerVal)

  API to write the counter value for RTC.

• uint16_t RTC_ReadCounter (void)

  API to read the counter clock cycle value from counter register.

• void RTC_WritePeriod (uint16_t timerVal)

  API to write the counter value to load for RTC.

• uint16_t RTC_ReadPeriod (void)

  API to read the overflow value in period register.

• void RTC_EnableCMPInterrupt (void)

  Enable the CMP interrupt to set the flag, if match value between counter register and compare register.

• void RTC_DisableCMPInterrupt (void)

  Disable the CMP interrupt for RTC interface.

• void RTC_EnableOVFInterrupt (void)

  Enable the overflow interrupt set the OVF flag, if the counter reached value from the period register and wrapped to zero.

• void RTC_DisableOVFInterrupt (void)

  Disable the Overflow interrupt for RTC interface.

• void RTC_EnablePITInterrupt (void)

  Enable the Period Interrupt Timer to set the flag, if a time period has passed as configured in period bit field.

• void RTC_DisablePITInterrupt (void)

  Disable the PIT interrupt for RTC interface.

• void RTC_ClearOVFInterruptFlag (void)

  Clearing the Overflow interrupt flag after the overflow flag set.

• bool RTC_IsOVFInterruptEnabled (void)

  Enable the Overflow interrupt to set overflow flag, when overflow occur.

• void(* RTC_OVF_isr_cb )(void) = NULL

• void(* RTC_CMP_isr_cb )(void) = NULL

• void(* RTC_PIT_isr_cb )(void) = NULL

This file contains the driver code for RTC module.

RTC Generated Driver File

version RTC Driver Version 2.0.3

• void RTC_SetOVFIsrCallback (RTC_cb_t cb)

  Isr callback function to be called if overflow interrupt flag is set.

• void RTC_SetCMPIsrCallback (RTC_cb_t cb)

  Isr callback function to be called if Compare match interrupt flag is set.

• void RTC_SetPITIsrCallback (RTC_cb_t cb)

  Isr callback function to be called if PIT interrupt flag is set.

• int8_t RTC_Initialize (void)

  Initialize RTC interface.

• void RTC_Start (void)

  API to start the counter register for RTC interface.

• void RTC_Stop (void)

  API to stop the counter register for RTC interface.

• void RTC_WriteCounter (uint16_t timerVal)

  API to write the counter value for RTC.

• void RTC_WritePeriod (uint16_t timerVal)

  API to write the counter value to load for RTC.

• uint16_t RTC_ReadCounter (void)

  API to read the counter clock cycle value from counter register.

• uint16_t RTC_ReadPeriod (void)

  API to read the overflow value in period register.

• void RTC_EnableCMPInterrupt (void)

  Enable the CMP interrupt to set the flag, if match value between counter register and compare register.

• void RTC_DisableCMPInterrupt (void)

  Disable the CMP interrupt for RTC interface.

• void RTC_EnableOVFInterrupt (void)

  Enable the overflow interrupt set the OVF flag, if the counter reached value from the period register and wrapped to zero.

• void RTC_DisableOVFInterrupt (void)

  Disable the Overflow interrupt for RTC interface.

• void RTC_EnablePITInterrupt (void)

  Enable the Period Interrupt Timer to set the flag, if a time period has passed as configured in period bit field.

• void RTC_DisablePITInterrupt (void)

  Disable the PIT interrupt for RTC interface.

• void RTC_ClearOVFInterruptFlag (void)

  Clearing the Overflow interrupt flag after the overflow flag set.

• bool RTC_IsOVFInterruptEnabled (void)

  Enable the Overflow interrupt to set overflow flag, when overflow occur.

• typedef void(* RTC_cb_t) (void)

  Function pointer to callback function called by RTC. NULL=default value: No callback function is to be used.

This header file provides APIs for the RTC driver.

RTC Generated Driver API Header File

defgroup rtc RTC