MSP432P401R: DriverLib example: Measuring internal temperature

/*
 * -------------------------------------------
 *    MSP432 DriverLib - v4_00_00_11
 * -------------------------------------------
 *
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 * Copyright (c) 2017, Texas Instruments Incorporated
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/*******************************************************************************
 * MSP432 ADC14 - Single Channel Repeat Temperature Sensor
 *
 * Description: This example shows the use of the internal temperature sensor.
 * A simple continuous ADC sample/conversion is set up with a software trigger.
 * The sample time is set to TBD as speced by the User's Guide. All calculations
 * take place in the ISR which take advantage of the Stacking Mode of the FPU.
 * The temperature is calculated in both Celsius and Fahrenheit.
 *
 *                MSP432P401
 *             ------------------
 *         /|\|                  |
 *          | |                  |
 *          --|RST         P5.5  |
 *            |                  |
 *            |                  |
 *            |                  |
 *
 * Author: Timothy Logan
 ******************************************************************************/
/* DriverLib Includes */
#include <ti/devices/msp432p4xx/driverlib/driverlib.h>

/* Standard Includes */
#include <stdint.h>

#include <string.h>

volatile uint32_t cal30;
volatile uint32_t cal85;
volatile float calDifference;
volatile float tempC;
volatile float tempF;

int main(void)
{
    /* Halting WDT  */
    WDT_A_holdTimer();
    Interrupt_enableSleepOnIsrExit();

    /* Enabling the FPU with stacking enabled (for use within ISR) */
    FPU_enableModule();
    FPU_enableLazyStacking();

    /* Initializing ADC (MCLK/1/1) with temperature sensor routed */
    ADC14_enableModule();
    ADC14_initModule(ADC_CLOCKSOURCE_MCLK, ADC_PREDIVIDER_1, ADC_DIVIDER_1,
            ADC_TEMPSENSEMAP);

    /* Configuring ADC Memory (ADC_MEM0 A22 (Temperature Sensor) in repeat
     * mode).
     */
    ADC14_configureSingleSampleMode(ADC_MEM0, true);
    ADC14_configureConversionMemory(ADC_MEM0, ADC_VREFPOS_INTBUF_VREFNEG_VSS,
            ADC_INPUT_A22, false);

    /* Configuring the sample/hold time for 192 */
    ADC14_setSampleHoldTime(ADC_PULSE_WIDTH_192,ADC_PULSE_WIDTH_192);

    /* Enabling sample timer in auto iteration mode and interrupts*/
    ADC14_enableSampleTimer(ADC_AUTOMATIC_ITERATION);
    ADC14_enableInterrupt(ADC_INT0);

    /* Setting reference voltage to 2.5 and enabling temperature sensor */
    REF_A_enableTempSensor();
    REF_A_setReferenceVoltage(REF_A_VREF2_5V);
    REF_A_enableReferenceVoltage();

    cal30 = SysCtl_getTempCalibrationConstant(SYSCTL_2_5V_REF,
            SYSCTL_30_DEGREES_C);
    cal85 = SysCtl_getTempCalibrationConstant(SYSCTL_2_5V_REF,
            SYSCTL_85_DEGREES_C);
    calDifference = cal85 - cal30;

    /* Enabling Interrupts */
    Interrupt_enableInterrupt(INT_ADC14);
    Interrupt_enableMaster();

    /* Triggering the start of the sample */
    ADC14_enableConversion();
    ADC14_toggleConversionTrigger();

    /* Going to sleep */
    while (1)
    {
        PCM_gotoLPM0();
    }
}

/* This interrupt happens every time a conversion has completed. Since the FPU
 * is enabled in stacking mode, we are able to use the FPU safely to perform
 * efficient floating point arithmetic.*/
void ADC14_IRQHandler(void)
{
    uint64_t status;
    int16_t conRes;

    status = ADC14_getEnabledInterruptStatus();
    ADC14_clearInterruptFlag(status);

    if(status & ADC_INT0)
    {
        conRes = ((ADC14_getResult(ADC_MEM0) - cal30) * 55);
        tempC = (conRes / calDifference) + 30.0f;
        tempF = tempC * 9.0f / 5.0f + 32.0f;
    }

}