MSP432P401R: DriverLib example: Measuring internal temperature

Part Number:MSP432P401R

I am using the DriverLib ADC14 example that measures the internal temperature of the chip I am using the new red Launchpad:

/*******************************************************************************
 * 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 "driverlib.h"

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

#include <string.h>

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_AVCC_VREFNEG_VSS,
            ADC_INPUT_A22, false);

    /* Configuring the sample/hold time for TBD */
    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_setReferenceVoltage(REF_A_VREF2_5V);
    REF_A_enableReferenceVoltage();
    REF_A_enableTempSensor();

    /* 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;
    uint32_t cal30, cal85;

    status = ADC14_getEnabledInterruptStatus();
    ADC14_clearInterruptFlag(status);

    if(status & ADC_INT0)
    {
        cal30 = SysCtl_getTempCalibrationConstant(SYSCTL_2_5V_REF,
                SYSCTL_30_DEGREES_C);
        cal85 = SysCtl_getTempCalibrationConstant(SYSCTL_2_5V_REF,
                SYSCTL_85_DEGREES_C);

        tempC = (float) (((uint32_t) ADC14_getResult(ADC_MEM0) - cal30) * (85 - 30))
                / (cal85 - cal30) + 30.0f;
        tempF = tempC * 9.0f / 5.0f + 32.0f;
    }

}

When I run it, cal30 = 4702, cal85 = 5401 and my ADC reads about 3500.

Firstly:

In case someone measures temp below 30 C, I think you should make all the int variables signed. I got really confused when I measured a huge temperature. 8^)

However, even after I fixed that, I still measured about -60C, which is obviously not correct. What am I doing wrong?