MSP430 Pentax IR intervalometer 2

#include <msp430.h>
#include <signal.h>

#define IR_LED      BIT6
#define TRIGGER     BIT3
#define STATUS_LED  BIT0

static volatile int cycle_count;                    // IR carrier cycle count
unsigned long time = 0;                             // current time, 1 click = 32.8ms
unsigned long last_shot = 0;                        // time of last manual shot
unsigned long interval = 100;                       // currently set interval
unsigned long trigger_down_time = 0;                // time button was depressed
int trigger_down = 0;
int interval_on = 0;
int manual_shot = 0;

#pragma vector = WDT_VECTOR
__interrupt void wdt_isr(void)
{
    time++;
    __bic_SR_register_on_exit(LPM1_bits);
}

#pragma vector = TIMERA0_VECTOR                     // Timer A Capture/Compare 0 interrupt
__interrupt void timera0_isr(void)                  // This ISR must be very simple because there may
                                                    // be as few as 16 cycles available for it to complete
{                                                   //
    --cycle_count;                                  // Decrement cycle count
}

#pragma vector = PORT1_VECTOR
__interrupt void port1_isr(void)
{
    if (P1IFG & TRIGGER)
    {
        P1IES ^= TRIGGER;                           // switch interrupt direction
        trigger_down = !trigger_down;               // toggle state
        trigger_down_time = time;
        manual_shot = trigger_down;
        __bic_SR_register_on_exit(LPM1_bits);
    }

    P1IFG = 0;                                     // clear p1 interrupts
}



static const int pentax[] = {
    26,                                             // Carrier period in us ( 1 MHz / 38 kHz ~= 26 )
    8,                                              // Number of pairs
    500, 115,                                       // 13 ms on, 3 ms off
    38, 39,                                         // 1 ms on, 1 ms off
    38, 39,                                         // 1 ms on, 1 ms off
    38, 39,                                         // 1 ms on, 1 ms off
    38, 39,                                         // 1 ms on, 1 ms off
    38, 39,                                         // 1 ms on, 1 ms off
    38, 39,                                         // 1 ms on, 1 ms off
    38, 39                                          // 1 ms on, 1 ms off
};

void send_code(const int *code)
{
    TACCR0 = *code++ - 1 ;                          // Set timer period
    TACCR1 = TACCR0 >> 1;                           // Set timer on duration - 50% duty cycle
    int pair = *code++;                             // Get pair count
    cycle_count = 5;                                // Setup some initial IR off lead in
    TACCTL0 = CCIE;                                 // Enable Timer A CC0 interrupt
    do {                                            // Do all pairs
        int cc = *code++;                           // Get on cycles
        while(cycle_count > 0);                     // Wait for off cycles to complete
        TACCTL1 = OUTMOD_7;                         // Turn on IR
        cycle_count += cc;                          // Set on cycle count
        cc = *code++;                               // Get off cycles
        while(cycle_count > 0);                     // Wait for on cycles to complete
        TACCTL1 = OUTMOD_0;                         // Turn off IR
        cycle_count += cc;                          // Set off cycle count
    } while(--pair);                                // Decrement pair count, do next pair if not zero
    while(cycle_count > 0);                         // Wait for off cycles to complete
    TACCTL0 = 0;                                    // Turn off Timer A CC0 interrupt
}

int main(void)
{
    WDTCTL = WDTPW | WDTHOLD;                       // Disable watchdog reset
    DCOCTL = 0;                                     // Run at 1 MHz
    BCSCTL1 = CALBC1_1MHZ;                          //
    DCOCTL = CALDCO_1MHZ;                           //

    P1DIR |= TRIGGER;                               // Set P1.3 to input
    P1IE  |= TRIGGER;                               // P1.3 enabled interrupts
    P1IES |= TRIGGER;                               // P1.3 Hi/lo edge
    P1IFG &= ~TRIGGER;                              // P1.3 clear IFG

    TACTL = TASSEL_2 | MC_1;                        // Timer A config: SMCLK, count up
    TACCTL1 = OUTMOD_0;                             // Make sure IR is off

    P1OUT = IR_LED;
    P1DIR = STATUS_LED | IR_LED;                    // Enable PWM output on P1.6
    P1SEL = IR_LED;

    WDTCTL = WDTPW | WDTTMSEL | WDTCNTCL;
    IE1 |= WDTIE;

    eint();                                         // Enable global interrupts

    while(1) {
        if (interval_on && (time - last_shot >= interval)) // intervalometer
        {
            send_code(pentax);                      // Send Pentax IR code
            last_shot = time;
        }

        if (manual_shot)                            // manual triggering
        {
            manual_shot = 0;
            send_code(pentax);
            interval = time - last_shot;            // save interval
            interval = (interval > 15? interval: 15);
            last_shot = time;
        }

        if (trigger_down && (time - trigger_down_time) > 30)
                                                    //  hold button for 1 sec to switch modes
        {
            trigger_down_time = time;
            interval_on = !interval_on;
            if (interval_on)
                P1OUT ^= STATUS_LED;
            else
                P1OUT &= ~STATUS_LED;
        }

        __bis_SR_register(LPM1_bits + GIE);
    }
    return 1;
}