MSP430FR231x LPM3.5

msp430fr231x_lpm_3_5_01.c

#include <msp430.h>

void initGpio(void);

int main(void)
{
    WDTCTL = WDTPW | WDTHOLD;               // Stop WDT
    initGpio();                             // Configure GPIO
    // Initialize XT1 32kHz crystal
    P2SEL1 |= BIT6 | BIT7;                  // P2.6~P2.7: crystal pins
    do
    {
        CSCTL7 &= ~(XT1OFFG | DCOFFG);      // Clear XT1 and DCO fault flag
        SFRIFG1 &= ~OFIFG;
    } while (SFRIFG1 & OFIFG);              // Test oscillator fault flag

    // First determine whether we are coming out of an LPMx.5 or a regular RESET.
    if (SYSRSTIV == SYSRSTIV_LPM5WU)        // When woken up from LPM3.5, reinit
    {
        // If MCU wakes up from LPM3.5, re-init and then return to LPM3.5 again.
        // Restore P1OUT value from backup RAM memory, keep P1OUT after LPMx.5 reset
        P1OUT = *(unsigned int *)BKMEM_BASE;
        __enable_interrupt();               // The RTC interrupt should trigger now...
    }
    else
    {
        // Device powered up from a cold start.
        // It configures the device and puts the device into LPM3.5
        // Configure backup memory
        *(unsigned int *)BKMEM_BASE = 0;
        // Configure RTC
        // Interrupt and reset happen every 1024/32768 * 32 = 1 sec.
        RTCMOD = (32)-1;
        RTCCTL = RTCSS__XT1CLK | RTCSR |RTCPS__1024;
        RTCCTL |= RTCIE;
        // Store P1OUT value in backup memory register before enter LPM3.5
        *(unsigned int *)BKMEM_BASE = P1OUT;
    }

    // Enter LPM3.5 mode with interrupts enabled. Note that this operation does
    // not return. The LPM3.5 will exit through a RESET event, resulting in a
    // re-start of the code.
    PMMCTL0_H = PMMPW_H;                    // Open PMM Registers for write
    PMMCTL0_L |= PMMREGOFF;                 // and set PMMREGOFF
    __bis_SR_register(LPM3_bits | GIE);
    __no_operation();

    return 0;
}

void initGpio(void)
{
    P1DIR = 0xFF; P2DIR = 0xFF;
    P1REN = 0xFF; P2REN = 0xFF;
    P1OUT = 0x00; P2OUT = 0x00;
    // Disable the GPIO power-on default high-impedance mode
    // to activate previously configured port settings
    PM5CTL0 &= ~LOCKLPM5;
}

#if defined(__TI_COMPILER_VERSION__) || defined(__IAR_SYSTEMS_ICC__)
#pragma vector = RTC_VECTOR
__interrupt void RTC_ISR(void)
#elif defined(__GNUC__)
void __attribute__ ((interrupt(RTC_VECTOR))) RTC_ISR (void)
#else
#error Compiler not supported!
#endif
{
    switch(__even_in_range(RTCIV, RTCIV_RTCIF))
    {
        case RTCIV_NONE : break;            // No interrupt pending
        case RTCIV_RTCIF:                   // RTC Overflow
            // Toggle P1.6
            P1OUT ^= BIT6;
            // Store P1OUT value in backup memory register
            *(unsigned int *)BKMEM_BASE = P1OUT;
            break;
        default:          break;
    }
}