MSP430FR4133 Internal Temperature Sensor

Question

I am currently using the MSP430FR4133 in order to make an ultrasonic measurement system for the volume of a room and would like to be able to check the temperature of a room to work out the speed of sound before I carry out any calculations. I am trying to use the code in the "Out-the-Box Software Example" that uses the temperature sensor to display the temperature in Celsius and Fahrenheit. This folder is found at: http://software-dl.ti.com/msp430/msp430_public_sw/mcu/msp430/MSP-EXP430FR4133/latest/index_FDS.html.

My code is as follows:

main.c

#include <msp430.h>
#include <driverlib.h>
#include "hal_LCD.h"
#include "InputOutput.h"
#include "Temp.h"
#include "Displays.h"

#define PORT1_VECTOR        (47 * 2u)
#define TIMER1_A0_VECTOR    (54 * 2u) 

char introduction[6] = "HELLO";

int main(void)
{
WDTCTL = WDTPW | WDTHOLD;               // Stop watchdog timer

tempInit();
InitInputs();
InitOutputs();
Init_LCD();
double speedofsound = tempInit();
displayScrollText(introduction);

// Disable the GPIO power-on default high-impedance mode
// to activate previously configured port settings
PMM_unlockLPM5();

while(1)
{
      double distance[3];
      double time[3];
      double volume = 0;

      displayLength();
      SW1();
      displayWait();
      time[0] = SW2();
      displayWidth();
      SW1();
      displayWait();
      time[1] = SW2();
      displayHeight();
      SW1();
      displayWait();
      time[2] = SW2();

      for(int i =0;i<3;i++)
      {
            distance[i] = time[i]*speedofsound;
      }

      volume = distance[0]*distance[1]*distance[2];
      displayVolume(volume);
    }
}

Temp.c

#include <msp430.h>
#include <driverlib.h>
#include "hal_LCD.h"
#include "Temp.h"

#define CALADC_15V_30C  *((unsigned int *)0x1A1A)       // Temperature Sensor Calibration-30 C
#define CALADC_15V_85C  *((unsigned int *)0x1A1C)       // Temperature Sensor Calibration-85 C

volatile unsigned char * tempUnit = &BAKMEM4_H;
volatile int *degC = &BAKMEM5;                          // Celcius measurement
volatile unsigned char * tempSensorRunning = &BAKMEM3_H;      // Temp Sensor running flag
int deg;

Timer_A_initUpModeParam initUpParam_A1 =
{
    TIMER_A_CLOCKSOURCE_ACLK,               // ACLK Clock Source
    TIMER_A_CLOCKSOURCE_DIVIDER_1,          // ACLK/1 = 32768Hz
    0x2000,                                 // Timer period
    TIMER_A_TAIE_INTERRUPT_DISABLE,         // Disable Timer interrupt
    TIMER_A_CCIE_CCR0_INTERRUPT_DISABLE ,   // Disable CCR0 interrupt
    TIMER_A_DO_CLEAR                        // Clear value
};

Timer_A_initCompareModeParam initCompParam =
{
    TIMER_A_CAPTURECOMPARE_REGISTER_1,        // Compare register 1
    TIMER_A_CAPTURECOMPARE_INTERRUPT_DISABLE, // Disable Compare interrupt
    TIMER_A_OUTPUTMODE_RESET_SET,             // Timer output mode 7
    0x1000                                    // Compare value
};

double tempInit()
{
  *tempSensorRunning ^= 0x01;
  *tempSensorRunning =1;
  //Initialize the ADC Module
  /*
   * Base Address for the ADC Module
   * Use Timer trigger 1 as sample/hold signal to start conversion
   * USE MODOSC 5MHZ Digital Oscillator as clock source
   * Use default clock divider of 1
   */
  ADC_init(ADC_BASE,ADC_SAMPLEHOLDSOURCE_2,ADC_CLOCKSOURCE_ADCOSC,ADC_CLOCKDIVIDER_1);

ADC_enable(ADC_BASE);

//Configure Memory Buffer
/*
 * Base Address for the ADC Module
 * Use input A12 Temp Sensor
 * Use positive reference of Internally generated Vref
 * Use negative reference of AVss
 */
    ADC_configureMemory(ADC_BASE,ADC_INPUT_TEMPSENSOR,ADC_VREFPOS_INT,ADC_VREFNEG_AVSS);

    ADC_clearInterrupt(ADC_BASE, ADC_COMPLETED_INTERRUPT);

    // Enable the Memory Buffer Interrupt
    ADC_enableInterrupt(ADC_BASE,ADC_COMPLETED_INTERRUPT);

    ADC_startConversion(ADC_BASE, ADC_REPEATED_SINGLECHANNEL);

    // Enable internal reference and temperature sensor
    PMM_enableInternalReference();
    PMM_enableTempSensor();

    // TimerA1.1 (125ms ON-period) - ADC conversion trigger signal
    Timer_A_initUpMode(TIMER_A1_BASE, &initUpParam_A1);

    //Initialize compare mode to generate PWM1
    Timer_A_initCompareMode(TIMER_A1_BASE, &initCompParam);

    // Start timer A1 in up mode
    Timer_A_startCounter(TIMER_A1_BASE, TIMER_A_UP_MODE);

    // Delay for reference settling
    __delay_cycles(300000);

    while(*tempSensorRunning)
    {
        __bis_SR_register(LPM3_bits | GIE);                       // LPM3 with interrupts enabled
        //__no_operation();                                         // Only for debugger

        // Calculate Temperature in degree C and F
        signed short temp = (ADCMEM0 - CALADC_15V_30C);
        *degC =((long)temp * 10 * (85-30) * 10)/((CALADC_15V_85C-CALADC_15V_30C)*10) + 300;

        *tempSensorRunning = 0;
    }
    double speed = 331+0.6*(*degC);
    return speed;
    };

I have made slight adjustments to the code in order to find the speed of sound for the temperature of the room, however this code does not seem to work. I get a warning a value of type "unsigned short volatile *" cannot be used to initialize an entity of type "int volatile *"(line 10 of Temp.c) which I don't think is effecting my code, however I am unsure on how to correct this.

When I set breakpoints within the code I is seen that at if(*tempSensorRunning)the code runs into an endless loop. Can anyone please give me some advice for this problem?

EDIT:

I have changed the code for Temp.c slightly to illustrate the suggested changes. Having set breakpoints throughout the code I can see that the problem is occuring at signed short temp = (ADCMEM0 - CALADC_15V_30C);. The code is stopping here and not moving past this point. The disassembly is staying at the point:

?reset_vector:
010000

Can anyone explain what is happening here?

Answer 1

The variable tempSensorRunning is set to 1 in the line:

*tempSensorRunning = 1;

and never (at least in this code) cleared to 0, so that's where your infinite loop comes from.

This device is a 16-bit MCU, so int in this case is 16-bits long. In any case, this is confusing, so to be sure you're using the correct bit width for accesses (especially as you're accessing data via pointers), include <stdint.h> and be explicit:

• uint8_t for unsigned 8-bit numbers
• uint16_t for unsigned 16-bit numbers

Answer 2

I assume the warning comes from this line:

volatile int *degC = &BAKMEM5;

Apparently BAKMEM5 is a short, not an int. The way to correct it is to change the type of degC to volatile short *. This fix may have ripple effects. You have to use the right types consistently.

This is likely an actual bug and not just a warning you can ignore.