MSP430FR4133: RTC running under LPM0 fails when interrupts on P1.2 or P2.6 are set

The LPM0 exit statement was moved to be right after the RTC_clearInterrupt statement, but while the loop still works fine, it still fails with P2.6 interrupt vector enable. Secondly, I thought both of these statements were unnecessary as they were automatic with the RTC interrupt. This is way above my pay grade, I hope someone helps with this. R.

The following statements are for NO Px pins being interrupt enabled. Just for the

//    RTC_clearInterrupt(RTC_BASE, RTC_OVERFLOW_INTERRUPT_FLAG);
//  __bic_SR_register_on_exit(LPM0_bits);

statements at the top of the routine.

First, when the two extra statements at the top of the interrupt routine are there, everything works fine. Second, when they are not there, the interrupts are coming so fast the LED is blinking at least 10 times a second, and no modulo settings affect it.  Dare I say oscillating?

When either of the two Px pins are interrupt enabled, with or without these two statements, there are no interrupts at all.

The real question here is why setting the interrupt enables on Px pins affects the RTC at all. It is going to take an expert to fix this! R.

Yes, you do have to clear the RTC interrupt explicitly in the ISR. I don't see anything in the User Guide (SLAU445H) which suggests otherwise.

In a bit of a curiosity, despite the statement (UG Table 15-2) that RTCIFG (aka RTCIF) is read-only and clearable only using the RTCIV, observed behavior is that it can be directly cleared.

I wrapped your code fragments and ran it on a Launchpad, and I get the results I expect: (a) if the ISR clears the RTC interrupt, it blinks 1/second. (b) if the ISR does not clear the interrupt, it blinks faster (probably 5/sec due to the __delay-s). I see no side-effect from enabling (or not) the pin interrupts.

I'm not sure what you and I are doing differently.

#include "driverlib.h"
int main(void)
{
    WDT_A_hold(WDT_A_BASE);

    //  RTC setup lifted from Example rtc_ex1_countmode.c
    GPIO_setAsOutputPin( GPIO_PORT_P1, GPIO_PIN0);
    PMM_unlockLPM5();       // Engage GPIOs
    //Set DCO FLL reference = REFO
    CS_initClockSignal( CS_FLLREF, CS_REFOCLK_SELECT, CS_CLOCK_DIVIDER_1);
    //Set ACLK = REFO
    CS_initClockSignal(CS_ACLK, CS_REFOCLK_SELECT, CS_CLOCK_DIVIDER_1);

    //Initialize RTC
#define INTERVAL_TIME 32768
    RTC_init(RTC_BASE, INTERVAL_TIME, RTC_CLOCKPREDIVIDER_1);
    RTC_clearInterrupt(RTC_BASE, RTC_OVERFLOW_INTERRUPT_FLAG);
    RTC_enableInterrupt(RTC_BASE, RTC_OVERFLOW_INTERRUPT);
    RTC_start(RTC_BASE, RTC_CLOCKSOURCE_XT1CLK);

    // Configure buttons, from E2E item:
    // Configure button S1 (P1.2) interrupt
    GPIO_selectInterruptEdge(GPIO_PORT_P1, GPIO_PIN2, GPIO_HIGH_TO_LOW_TRANSITION);
    GPIO_setAsInputPinWithPullUpResistor(GPIO_PORT_P1, GPIO_PIN2);
    GPIO_clearInterrupt(GPIO_PORT_P1, GPIO_PIN2);
    GPIO_enableInterrupt(GPIO_PORT_P1, GPIO_PIN2);

    // Configure button S2 (P2.6) interrupt
    GPIO_selectInterruptEdge(GPIO_PORT_P2, GPIO_PIN6, GPIO_HIGH_TO_LOW_TRANSITION);
    GPIO_setAsInputPinWithPullUpResistor(GPIO_PORT_P2, GPIO_PIN6);
    GPIO_clearInterrupt(GPIO_PORT_P2, GPIO_PIN6);
    GPIO_enableInterrupt(GPIO_PORT_P2, GPIO_PIN6);

    while (1)
    {
        __bis_SR_register(LPM0_bits | GIE);         // GO TO SLEEP
        __no_operation();         // End of main loop
    }
    /*NOTREACHED*/
    return (0);
}

unsigned long IReturn; // uint32_t per E2E
#pragma vector = RTC_VECTOR
__interrupt void RTC_ISR(void)
{
    RTC_clearInterrupt(RTC_BASE, RTC_OVERFLOW_INTERRUPT_FLAG);
    __bic_SR_register_on_exit(LPM0_bits); //edit, this now appears at the top of the ISR routine
    P1OUT |= BIT0;    // Turn LED1 On/
    __delay_cycles(100000);
    IReturn = IReturn + 10;
    P1OUT &= ~BIT0;    // Turn LED1 off
    __delay_cycles(100000);
}

#pragma vector=PORT1_VECTOR
__interrupt void P1_ISR(void)
{
    P1IFG = 0;        // Muzzle and ignore
    return;
}
#pragma vector=PORT2_VECTOR
__interrupt void P2_ISR(void)
{
    P2IFG = 0;        // Muzzle and ignore
    return;
}