CCS/MSP432P401R: Using MSP432 Internal Comparator to Measure Frequency

/*
 * -------------------------------------------
 *    MSP432 DriverLib - v3_21_00_05 
 * -------------------------------------------
 *
 * --COPYRIGHT--,BSD,BSD
 * Copyright (c) 2016, Texas Instruments Incorporated
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * *  Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * *  Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * *  Neither the name of Texas Instruments Incorporated nor the names of
 *    its contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
 * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 * --/COPYRIGHT--*/
/*******************************************************************************
* MSP432 Timer_A - VLO Period Capture
*
* Description: Capture a number of periods of the VLO clock and store them in
* an array. When the set number of periods is captured the program is trapped
* and the LED on P1.0 is toggled. At this point halt the program execution read
* out the values using the debugger.
* ACLK = VLOCLK = 14kHz (typ.), MCLK = SMCLK = default DCO  = 3MHz
*
*                MSP432P401
*             ------------------
*         /|\|                  |
*          | |                  |
*          --|RST         P1.0  |---> P1.0 LED
*            |            P2.4  |--- TA0.1
*            |                  |   |
*            |            P4.2  |--- ACLK
*            |                  |
* Author: Timothy Logan
*******************************************************************************/
/* DriverLib Includes */
#include "driverlib.h"

/* Standard Includes */
#include <stdint.h>
#define NUMBER_TIMER_CAPTURES       20

/* Timer_A Continuous Mode Configuration Parameter */
const Timer_A_ContinuousModeConfig continuousModeConfig =
{
        TIMER_A_CLOCKSOURCE_SMCLK,           // SMCLK Clock Source
        TIMER_A_CLOCKSOURCE_DIVIDER_1,       // SMCLK/1 = 3MHz
        TIMER_A_TAIE_INTERRUPT_DISABLE,      // Disable Timer ISR
        TIMER_A_SKIP_CLEAR                   // Skup Clear Counter
};

/* Timer_A Capture Mode Configuration Parameter */
const Timer_A_CaptureModeConfig captureModeConfig =
{
        TIMER_A_CAPTURECOMPARE_REGISTER_1,        // CC Register 2
        TIMER_A_CAPTUREMODE_RISING_EDGE,          // Rising Edge
        TIMER_A_CAPTURE_INPUTSELECT_CCIxB,        // CCIxB Input Select
        TIMER_A_CAPTURE_SYNCHRONOUS,              // Synchronized Capture
        TIMER_A_CAPTURECOMPARE_INTERRUPT_ENABLE,  // Enable interrupt
        TIMER_A_OUTPUTMODE_OUTBITVALUE            // Output bit value
};

/* Statics */
static volatile uint_fast16_t timerAcaptureValues[NUMBER_TIMER_CAPTURES];
static volatile uint32_t timerAcapturePointer = 0;


int main(void)
{
    /* Stop watchdog timer */
    MAP_WDT_A_holdTimer();

    /* Configuring P1.0 as output */
    MAP_GPIO_setAsOutputPin(GPIO_PORT_P1, GPIO_PIN0);

    /* Configuring P2.4 as peripheral input for capture and P4.2 for ACLK
     * output */
    MAP_GPIO_setAsPeripheralModuleFunctionOutputPin(GPIO_PORT_P4, GPIO_PIN2,
            GPIO_PRIMARY_MODULE_FUNCTION);
    MAP_GPIO_setAsPeripheralModuleFunctionInputPin(GPIO_PORT_P2, GPIO_PIN4,
            GPIO_PRIMARY_MODULE_FUNCTION);

    /* Setting ACLK = VLO = 14kHz */
    MAP_CS_initClockSignal(CS_ACLK, CS_VLOCLK_SELECT, CS_CLOCK_DIVIDER_1);

    /* Configuring Capture Mode */
    MAP_Timer_A_initCapture(TIMER_A0_BASE, &captureModeConfig);

    /* Configuring Continuous Mode */
    MAP_Timer_A_configureContinuousMode(TIMER_A0_BASE, &continuousModeConfig);

    /* Enabling interrupts and going to sleep */
    MAP_Interrupt_enableSleepOnIsrExit();
    MAP_Interrupt_enableInterrupt(INT_TA0_N);
    MAP_Interrupt_enableMaster();

    /* Starting the Timer_A0 in continuous mode */
    MAP_Timer_A_startCounter(TIMER_A0_BASE, TIMER_A_CONTINUOUS_MODE);

    MAP_PCM_gotoLPM0();

}

//******************************************************************************
//
//This is the TIMERA interrupt vector service routine.
//
//******************************************************************************
void TA0_N_IRQHandler(void)
{
    uint32_t jj;

    MAP_Timer_A_clearCaptureCompareInterrupt(TIMER_A0_BASE,
            TIMER_A_CAPTURECOMPARE_REGISTER_1);

    timerAcaptureValues[timerAcapturePointer++] =
            MAP_Timer_A_getCaptureCompareCount(TIMER_A0_BASE,
                                             TIMER_A_CAPTURECOMPARE_REGISTER_1);

    if (timerAcapturePointer >= NUMBER_TIMER_CAPTURES)
    {
        while (1)
        {
            MAP_GPIO_toggleOutputOnPin(GPIO_PORT_P1, GPIO_PIN0);
            for(jj=0;jj<10000;jj++);
        }
    }
}