MSP430FR6047: measuring integrated flow

Nakyoung,

The delay function in the code today will not provide very high precision as it is executed from the start of each measurement and it is possible that the algorithm computation can take a longer or shorter period depending on the data captured.  Also, it looks like you are measuring the logged data from the GUI, which could also have some variation creating the time stamp with the I2C communication and GUI interface.  

If you would like very precise timing, you could implement an interrupt timer based solution as shown below.  

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#pragma vector= USS_APP_PERIODIC_MEASUREMENT_TIMER_CCR0_VECTOR
__interrupt void USS_APP_PERIODIC_MEASUREMENT_TIMER_INT(void)
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Files that need modification:
1.	USS_App_userConfig.c:
2.	USS_App_userConfig.h:
3.	USSLibGUIApp.c

----------------------------------------------------------------------------
USSLibGUIApp.c:
----------------------------------------------------------------------------
/* Enables Timer Based capture frequency */
#ifdef USS_APP_PERIODIC_MEASUREMENT_TIMER_ENABLE
uint16_t captureCyclePeriod;
#endif

// For INITIALIZATION; NOT INSIDE THE WHILE LOOP ****
#ifdef USS_APP_PERIODIC_MEASUREMENT_TIMER_ENABLE
    // Initialize the Measurement (Capture) Timer duration
    captureCyclePeriod = USS_APP_CAPTURE_FREQ_ACLK;
    USS_APP_initCaptureTimer(captureCyclePeriod);
    USS_APP_startCaptureTimer();
#endif

// INSIDE THE WHILE LOOP: (Instead of the DELAY)

#ifndef USS_APP_PERIODIC_MEASUREMENT_TIMER_ENABLE
        if (gUssSWConfig.measurementConfig->pulseConfig->AFCisEnabled == false)
        {
            USSLibGUIApp_Delay();     /* Delay for proper time  */
        }
#else
        if (gUssSWConfig.measurementConfig->pulseConfig->AFCisEnabled == false)
        {
            USS_APP_waitForTimerInt();
            USS_APP_restartCaptureTimer();
        }
#endif
----------------------------------------------------------------------------
USS_App_userConfig.h:
----------------------------------------------------------------------------
/* Enables Timer Based capture frequency */
#ifdef USS_APP_PERIODIC_MEASUREMENT_TIMER_ENABLE
#define USS_APP_PERIODIC_MEASUREMENT_TIMER_BASE_ADDRESS (TIMER_A3_BASE)
#if (USS_APP_PERIODIC_MEASUREMENT_TIMER_BASE_ADDRESS==TIMER_A3_BASE)
#define USS_APP_PERIODIC_MEASUREMENT_TIMER_CCR0_VECTOR  (TIMER3_A0_VECTOR)
#endif
#endif
/* Delay time between captures in ACLK (32768Hz) cycles */
//Timer interrupt duration in ACLK cycles for capture frequency
#define USS_APP_CAPTURE_FREQ_SECONDS              (1)
#define USS_APP_CAPTURE_FREQ_ACLK                 ((32768-2)*USS_APP_CAPTURE_FREQ_SECONDS)

#ifdef USS_APP_PERIODIC_MEASUREMENT_TIMER_ENABLE
//! \brief function to initialize the Timer used to control the capture frequency
//!
extern void USS_APP_initCaptureTimer(uint16_t captureTimerCounts);

//! \brief function to start the Timer used to control the capture frequency
//!
extern void USS_APP_startCaptureTimer(void);

//! \brief function to restart the Timer used to control the capture frequency
//!
extern void USS_APP_restartCaptureTimer(void);

//! \brief function to wait for the timer interrupt to fire
//!
extern void USS_APP_waitForTimerInt(void);
#endif // end of USS_APP_PERIODIC_MEASUREMENT_TIMER_ENABLE
----------------------------------------------------------------------------
USS_App_userConfig.c:
----------------------------------------------------------------------------

#ifdef USS_APP_PERIODIC_MEASUREMENT_TIMER_ENABLE
volatile uint16_t timerSWFlag, timerOverflow;

void USS_APP_initCaptureTimer(uint16_t captureTimerCounts)
{
    //Init flags
    timerSWFlag = false;
    timerOverflow = false;
    // Timer uses ACLK. CLK Div /1. Stop mode. Clear TAR
    HARDWAREWREG16(USS_APP_PERIODIC_MEASUREMENT_TIMER_BASE_ADDRESS + OFS_TAxCTL) = (TASSEL__ACLK | ID__1 | MC__STOP | TACLR);
    // Disable CCR0 interrupt by default. Compare mode
    HARDWAREWREG16(USS_APP_PERIODIC_MEASUREMENT_TIMER_BASE_ADDRESS + OFS_TAxCCTL0) = 0x00;
    // TAx.0 used to trigger the start of the next capture sequence
    HARDWAREWREG16(USS_APP_PERIODIC_MEASUREMENT_TIMER_BASE_ADDRESS + OFS_TAxCCR0) = captureTimerCounts;
}

void USS_APP_startCaptureTimer(void)
{
    // Enable CCR0 interrupt
    HARDWAREWREG16(USS_APP_PERIODIC_MEASUREMENT_TIMER_BASE_ADDRESS + OFS_TAxCCTL0) = CCIE;
    // Start Timer in up mode
    HARDWAREWREG16(USS_APP_PERIODIC_MEASUREMENT_TIMER_BASE_ADDRESS + OFS_TAxCTL) = (TASSEL__ACLK | TACLR | MC__UP);
}

void USS_APP_restartCaptureTimer(void)
{
    // Restart Timer in up mode
    HARDWAREWREG16(USS_APP_PERIODIC_MEASUREMENT_TIMER_BASE_ADDRESS + OFS_TAxCTL) = (TASSEL__ACLK | TACLR | MC__UP);
}

void USS_APP_waitForTimerInt(void)
{
    __disable_interrupt();
    //If timerSWFlag is true at this point, then the interrupt has already fired and the timer has already stopped, thus signaling an overflow
    if( timerSWFlag == true )
    {
        timerOverflow = true;
    }
    //If there was no overflow, then wait in the while loop for the timer interrupt to fire
    else
    {
        while( timerSWFlag == false )
        {
            __bis_SR_register(LPM3_bits + GIE);
            __disable_interrupt();
        }
    }

    timerSWFlag = false; //Always clear the timerSWFlag when returning from the function to start a new capture sequence

    __bis_SR_register(GIE);

}

#pragma vector= USS_APP_PERIODIC_MEASUREMENT_TIMER_CCR0_VECTOR
__interrupt void USS_APP_PERIODIC_MEASUREMENT_TIMER_INT(void)
{
    //Stop the timer
    HARDWAREWREG16(USS_APP_PERIODIC_MEASUREMENT_TIMER_BASE_ADDRESS + OFS_TAxCTL) = (TASSEL__ACLK | ID__1 | MC__STOP | TACLR);

    //Set the Timer flag
    timerSWFlag = true;

    //Clear the interrupt flag and wake up from LPM3 on return
    HARDWAREWREG16(USS_APP_PERIODIC_MEASUREMENT_TIMER_BASE_ADDRESS + OFS_TAxCCTL0) &= ~(CCIFG);
    LPM3_EXIT;
}
#endif // end of USS_APP_PERIODIC_MEASUREMENT_TIMER_ENABLE