/**
 * \file timer.c
 * \brief MSP430 Timer B driver and blocking delay implementation.
 *
 * This module provides a millisecond-level blocking delay function using
 * low-power mode and global interrupts, as well as initialization for Timer B
 * in up mode to generate periodic 1ms interrupts.
 */

#include <stdint.h>
#include <msp430.h>
#include <driverlib.h>
#include "timer.h"

/**
 * \brief Block execution for a given number of milliseconds.
 *
 * Implements a blocking delay by entering LPM0 and waking up via the
 * Timer interrupt on each millisecond tick.
 *
 * \param ms Number of milliseconds to delay.
 */
void sleep(uint16_t ms) {
    while (ms--) {
        /* Enter low-power mode 0 with interrupts enabled */
        __bis_SR_register(LPM0_bits + GIE);
        /* No operation, wait for interrupt */
        __no_operation();
    }
}

/**
 * \brief Initialize Timer B0 in up mode to generate 1ms period interrupts.
 *
 * Configures Timer B0 to use SMCLK, no divider, and a period of 999 ticks
 * to achieve a 1ms overflow (assuming 1MHz SMCLK). Enables CCR0 interrupt
 * to exit low-power mode on each tick.
 */
void init_timer(void) {
    static Timer_B_initUpModeParam param = {0};

    /* Select SMCLK as clock source */
    param.clockSource = TIMER_B_CLOCKSOURCE_SMCLK;
    /* No division: tick = 1MHz / 1 = 1MHz */
    param.clockSourceDivider = TIMER_B_CLOCKSOURCE_DIVIDER_1;
    /* Period = 999 -> interrupt every 1000 ticks => 1ms */
    param.timerPeriod = 999;
    /* Disable interrupt on timer rollover (TBIE) */
    param.timerInterruptEnable_TBIE = TIMER_B_TBIE_INTERRUPT_DISABLE;
    /* Enable CCR0 interrupt on timer compare match */
    param.captureCompareInterruptEnable_CCR0_CCIE =
        TIMER_B_CAPTURECOMPARE_INTERRUPT_ENABLE;
    /* Clear timer and start immediately */
    param.timerClear = TIMER_B_DO_CLEAR;
    param.startTimer = true;

    /* Initialize and start Timer B0 in up mode */
    Timer_B_initUpMode(TB0_BASE, &param);
}

/**
 * \brief ISR for Timer0_B0 (CCR0) comparison event.
 *
 * Exits low-power mode 0 to resume the sleeping function.
 */
#pragma vector=TIMER0_B0_VECTOR
__interrupt void TIMER0_B0_ISR(void) {
    /* Clear LPM0 bits on exit to wake up CPU */
    __bic_SR_register_on_exit(LPM0_bits);
}