Annoy A Tron 2.0

Hey guys

Prank Wars started early this year, so i tried  to improve upon my old annoyatron.

main differences are: only one unified timer interrupt using WDT and WDT_ADLY_1000 and the possibility to put the thing into sleep mode e.g. you can set a time in hours minutes and seconds until the annoyatron becomes active. good for hiding.

my main concerns are :

• is there any way to improve the WDT timer accuracy without using ACLK
• is the code energy efficient? how much current does it eat, i don't have a scope and cannot check things like that
• how would one immitate a locust chirp ?

any feedback is welcome

#include "msp430g2231.h"

#define PIEZO BIT6
#define LED1 BIT0

#define TRUE 1
#define FALSE 0

unsigned short lfsr = 0xACE1u;

short hours = 0;
short minutes = 10;
short seconds = 0;
short sleeping = TRUE;

unsigned int getRnd (void);
void timer (void);
void initPWM (void);

unsigned i=0;
int LPMMode = 0;
void main(void)
{
	BCSCTL3 |= LFXT1S_2;                  // Set VLO

	WDTCTL = WDT_ADLY_1000;                // Set WDT to timer mode at 1000ms, with VLO this is 2740ms
	IE1 |= WDTIE;                        // Enable WDT+ interrupt

	P1DIR |= PIEZO + LED1;                     // P1.2 PWM output/P1.6 constant output
	P1OUT = 0;


	unsigned int delay = 1;
	while(TRUE)
	{
		if (sleeping) {
			P1OUT ^= LED1;
		} else {
			P1OUT ^= LED1;
		}
		if (i>delay && !sleeping )
		{
			CCTL1 = OUTMOD_6;      // Start P1.2 PWM output
			// WDTCTL = WDT_ADLY_250;   // Reset WDT+ timer to 250ms, with VLO source this is 685ms
			LPMMode = 0;
			_BIS_SR(LPM0_bits + GIE);      // Go to sleep
			CCTL1 = OUTMOD_0;
			i=0;
			delay = (getRnd() >> 7);
		}
		LPMMode = 3;
		_BIS_SR(LPM3_bits + GIE);// Enter LPM3 w/ interrupt
	}
}

// WDT+ ISR for time between beeps and reset for beep length
#pragma vector=WDT_VECTOR
__interrupt void watchdog_timer (void)
{
	if (sleeping) {
		LPMMode = 0;
		i = 0; // keeps or counter from overflowing
		// without having to put more stuff into the isr
		seconds -= 3;
		if ( seconds <= 0) { // count down timer until deployment
			// we are compensating for the LARGELY inaccurate vlo
			seconds = 60;
			if (minutes--<= 0) {
				minutes = 60;
				if (hours-- <= 0) {
					sleeping = seconds = minutes = hours = FALSE;
					P1SEL |= PIEZO;
					CCR0 = 42;                           // Set PWM parameters, CCR0 is PWM Period/2
					CCR1 = 21;                           // Duty cycle
					TACTL = TASSEL_2 + MC_3;
				}
			}
		}
	} else  {
		i++;
	}

	if(LPMMode == 3)
		_BIC_SR_IRQ(LPM3_bits);
	else if(LPMMode == 0)
		_BIC_SR_IRQ(LPM0_bits);
}

unsigned int getRnd ()
{
	lfsr = (lfsr >> 1) ^ (-(lfsr & 1u) & 0xB400u);
	return lfsr;
}

thanks, 

lastaid