MSP430F5418A: How can I read the internal temperature?

Hi Mechi,

Can you please share what values are you getting for temperatureDegC and temperatureDegF? 

Hi Aaron,

Thanks for the prompt reply.

Here's the code:

// Initializes the I/O devices (I/O ports' direction and output values, A2D conversion)
void InitDev()
{
//...

    /* The A/D Control Register */
  
   
  ADC12CTL0 = ADC12ON +  ADC12MSC + ADC12SHT03 + ADC12REFON;   // Sample 32 ADC12CLK cycles - turn REF on for Temperature.
                                                                                                                               // Multiple sample and conversion.
  ADC12CTL1 = ADC12SHP + ADC12DIV_7 + ADC12SSEL_1 + ADC12CONSEQ_1 ; // Sequence conversion, ADC12CLK: ACLK/8.

  /* Set the Conversion Memory Registers (a sequence that starts with A0 and ends with A1. */
  
  ADC12MCTL0 = ADC12INCH_2 + ADC12REF2_5V; // ADC12MEM0 will read A2 
  ADC12MCTL1 = ADC12INCH_3 + ADC12REF2_5V; // ADC12MEM1 will read A3 
  ADC12MCTL2 = ADC12INCH_1 + ADC12REF2_5V; // ADC12MEM2 will read A1 
  ADC12MCTL3 = ADC12INCH_0 + ADC12REF2_5V; // ADC12MEM3 - will read A0 
  ADC12MCTL4 = ADC12INCH_4 + ADC12REF2_5V; // ADC12MEM4 - will read A4 
  ADC12MCTL5 = ADC12INCH_5 + ADC12REF2_5V; // ADC12MEM5 - will read A5 
  ADC12MCTL6 = ADC12INCH_6 + ADC12REF2_5V; // ADC12MEM6 - will read A6 
  ADC12MCTL7 = ADC12INCH_10 + ADC12REF2_5V + ADC12EOS; // ADC12MEM7 - will read A10 -temperature sensor
                                                                                                                // End of Sequence for the last channel
  
  ADC12IE = 0x01; // A/D Interrupt Enable
}


// The A2D interrupt - called when the conversion of the last channel in the sequence is complete.
// Reads the channel digital values after conversion.
#pragma vector=ADC12_VECTOR
__interrupt void Sampler(void)
{
  while ( (ADC12IFG & ADC12BUSY) == 0); // ADC12IFG - Interrupt Flag

    smp_acc_0 += ADC12MEM0;
    smp_acc_1 += ADC12MEM1;
    smp_acc_2 += ADC12MEM2;
    smp_acc_3 += ADC12MEM3;
    smp_acc_4 += ADC12MEM4;
    smp_acc_5 += ADC12MEM5;
    smp_acc_6 += ADC12MEM6;
    smp_acc_7 += ADC12MEM7;   // temperature


  ADC12CTL0 &= ~ADC12ENC;       // Disable conversion
  ADC12CTL0 &= ~ADC12SC;   // Start A/D conversion
}

You were following my question from another thread.

Here too, this code worked with IAR. I went back to the example code (mentioned above) to see if all of the steps are done correctly.

The other A2D channels (Voltages, etc. are read with actual values) but the Temperature (ADC12MEM7) comes out with very very low values.

In the sample, the code for conversion:

    // Temperature in Celsius
    // ((A10/4096*1500mV) - 894mV)*(1/3.66mV) = (A10/4096*410) - 244
    // = (A10 - 2438) * (410 / 4096)
    IntDegC = ((temp - 2438) * 410) / 4096;

    // Temperature in Fahrenheit
    // ((A10/4096*1500mV) - 829mV)*(1/2.033mV) = (A10/4096*738) - 408
    // = (A10 - 2264) * (738 / 4096)
    IntDegF = ((temp - 2264) * 738) / 4096;

So the final value ends up being very very low...

I sometimes get readings of 0xb or 0xE or 0x7 in ADC12MEM7 - but nothing higher

What results do you get with msp430x54x_adc12_10.c ? (Just set a breakpoint and look at the variables.) That experiment will tell you which direction to look.

-----------------

>ADC12IE= 0x01;

This sets ADC12IE0, which will fire after the first conversion is done. Particularly with such a slow ADC clock (ACLK/8, SHT=256) this will be long before the ADC has reached MCTL7. Try:

>ADC12IE = ADC12IE7;   // Interrupt after the 8th conversion

-----------------

>  while ( (ADC12IFG & ADC12BUSY) == 0);

This test is backwards, so it either won't wait at all or will wait forever. With the IE change above, you don't need this test, but the proper form would be:

>  while ( (ADC12IFG & ADC12BUSY) != 0);

-----------------

Thanks for the very detailed answer!

I took all of your suggestions - but still I don't get temperature readings.

I ran the example (msp430x54x_adc12_10.c) - and I'm only getting values between 0x00 and 0x12 - in a cyclical manner (values go up from 0 - 5 - 10 - 16 and then back down to 0).

BTW - the constants for calculating Fahrenheit and Celcius are in the example itself.

Thanks again,

Mechi

>BTW - the constants for calculating Fahrenheit and Celcius are in the example itself.

What I see in the Example is:

> temperatureDegC = (float)(((long)temp - CALADC12_15V_30C) * (85 - 30)) /
>                                 (CALADC12_15V_85C - CALADC12_15V_30C) + 30.0f;

where the interesting constants are in your chip (I don't know what they are).

----------------

Where do you see the small-integer results?

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//******************************************************************************
//  MSP430F54x Demo - ADC12, Sample A10 Temp and Convert to oC and oF
//
//  Description: A single sample is made on A10 with reference to internal
//  1.5V Vref. Software sets ADC12SC to start sample and conversion - ADC12SC
//  automatically cleared at EOC. ADC12 internal oscillator times sample
//  and conversion. In Mainloop MSP430 waits in LPM4 to save power until
//  ADC10 conversion complete, ADC12_ISR will force exit from any LPMx in
//  Mainloop on reti.
//  ACLK = n/a, MCLK = SMCLK = default DCO ~ 1.045MHz, ADC12CLK = ADC12OSC
//
//  Uncalibrated temperature measured from device to devive will vary do to
//  slope and offset variance from device to device - please see datasheet.
//
//                MSP430F5438
//             -----------------
//         /|\|              XIN|-
//          | |                 |
//          --|RST          XOUT|-
//            |                 |
//            |A10              |
//
//   W. Goh
//   Texas Instruments Inc.
//   November 2008
//   Built with CCE Version: 3.2.2 and IAR Embedded Workbench Version: 4.11B
//******************************************************************************
#include <msp430.h>

volatile long temp;
volatile long IntDegF;
volatile long IntDegC;

int main(void)
{
  WDTCTL = WDTPW + WDTHOLD;                 // Stop WDT
  ADC12CTL0 = ADC12SHT0_8 + ADC12REFON + ADC12ON;
                                            // Internal ref = 1.5V
  ADC12CTL1 = ADC12SHP;                     // enable sample timer
  ADC12MCTL0 = ADC12SREF_1 + ADC12INCH_10;  // ADC i/p ch A10 = temp sense i/p
  ADC12IE = 0x001;                          // ADC_IFG upon conv result-ADCMEMO
  __delay_cycles(37);                       // 35us delay to allow Ref to settle
                                            // based on default DCO frequency.
                                            // See Datasheet for typical settle
                                            // time.
  ADC12CTL0 |= ADC12ENC;

  while(1)
  {
    ADC12CTL0 |= ADC12SC;                   // Sampling and conversion start

    __bis_SR_register(LPM4_bits + GIE);     // LPM0 with interrupts enabled
    __no_operation();

    // Temperature in Celsius
    // ((A10/4096*1500mV) - 894mV)*(1/3.66mV) = (A10/4096*410) - 244
    // = (A10 - 2438) * (410 / 4096)
    IntDegC = ((temp - 2438) * 410) / 4096;

    // Temperature in Fahrenheit
    // ((A10/4096*1500mV) - 829mV)*(1/2.033mV) = (A10/4096*738) - 408
    // = (A10 - 2264) * (738 / 4096)
    IntDegF = ((temp - 2264) * 738) / 4096;
    __no_operation();                       // SET BREAKPOINT HERE
  }
}

#if defined(__TI_COMPILER_VERSION__) || defined(__IAR_SYSTEMS_ICC__)
#pragma vector=ADC12_VECTOR
__interrupt void ADC12ISR (void)
#elif defined(__GNUC__)
void __attribute__ ((interrupt(ADC12_VECTOR))) ADC12ISR (void)
#else
#error Compiler not supported!
#endif
{
  switch(__even_in_range(ADC12IV,34))
  {
  case  0: break;                           // Vector  0:  No interrupt
  case  2: break;                           // Vector  2:  ADC overflow
  case  4: break;                           // Vector  4:  ADC timing overflow
  case  6:                                  // Vector  6:  ADC12IFG0
    temp = ADC12MEM0;                       // Move results, IFG is cleared
    __bic_SR_register_on_exit(LPM4_bits);   // Exit active CPU
    break;
  case  8: break;                           // Vector  8:  ADC12IFG1
  case 10: break;                           // Vector 10:  ADC12IFG2
  case 12: break;                           // Vector 12:  ADC12IFG3
  case 14: break;                           // Vector 14:  ADC12IFG4
  case 16: break;                           // Vector 16:  ADC12IFG5
  case 18: break;                           // Vector 18:  ADC12IFG6
  case 20: break;                           // Vector 20:  ADC12IFG7
  case 22: break;                           // Vector 22:  ADC12IFG8
  case 24: break;                           // Vector 24:  ADC12IFG9
  case 26: break;                           // Vector 26:  ADC12IFG10
  case 28: break;                           // Vector 28:  ADC12IFG11
  case 30: break;                           // Vector 30:  ADC12IFG12
  case 32: break;                           // Vector 32:  ADC12IFG13
  case 34: break;                           // Vector 34:  ADC12IFG14
  default: break;
  }
}

I attached the example which I followed.

The small values I read from ADC12MEM7 - in the interrupt. The other channels have much larger values...

The sample you show is really different than the only I downloaded...

One difference is this line:

  /* Initialize the shared reference module */
  REFCTL0 |= REFMSTR + REFVSEL_0 + REFON;    // Enable internal 1.5V reference

When I tried the sample you mentioned, there are no readings at all.

How can I transfer the Temperature reading to ADC12MEM7 - which is the only ADC channel free in our device?

This is what I tried - but the interrupt is not called:

int main(void)
{
  WDTCTL = WDTPW + WDTHOLD;                 // Stop WDT

  /* Initialize the shared reference module */
  REFCTL0 |= REFMSTR + REFVSEL_0 + REFON;    // Enable internal 1.5V reference

  /* Initialize ADC12_A */
  ADC12CTL0 = ADC12SHT0_8 + ADC12ON + ADC12REFON;            // Set sample time
  ADC12CTL1 = ADC12SHP;                     // Enable sample timer
  ADC12MCTL7 = ADC12SREF_1 + ADC12INCH_10;  // ADC input ch A10 => temp sense
  ADC12IE = ADC12IE7; //  0x0001            // ADC_IFG upon conv result-ADCMEMO

  __delay_cycles(75);                       // delay to allow Ref to settle
                                            // based on default DCO frequency.
                                            // See Datasheet for typical settle
                                            // time.
  ADC12CTL0 |= ADC12ENC;

  while(1)
  {
    ADC12CTL0 &= ~ADC12SC;
    ADC12CTL0 |= ADC12SC;                   // Sampling and conversion start

    __bis_SR_register(LPM4_bits + GIE);     // LPM4 with interrupts enabled
    __no_operation();

    // Temperature in Celsius. See the Device Descriptor Table section in the
    // System Resets, Interrupts, and Operating Modes, System Control Module
    // chapter in the device user's guide for background information on the
    // used formula.
    temperatureDegC = (float)(((long)temp - CALADC12_15V_30C) * (85 - 30)) /
            (CALADC12_15V_85C - CALADC12_15V_30C) + 30.0f;

    // Temperature in Fahrenheit Tf = (9/5)*Tc + 32
    temperatureDegF = temperatureDegC * 9.0f / 5.0f + 32.0f;

    __no_operation();                       // SET BREAKPOINT HERE
  }
}

#if defined(__TI_COMPILER_VERSION__) || defined(__IAR_SYSTEMS_ICC__)
#pragma vector=ADC12_VECTOR
__interrupt void ADC12ISR (void)
#elif defined(__GNUC__)
void __attribute__ ((interrupt(ADC12_VECTOR))) ADC12ISR (void)
#else
#error Compiler not supported!
#endif
{
  switch(__even_in_range(ADC12IV,34))
  {
  case  0: break;                           // Vector  0:  No interrupt
  case  2: break;                           // Vector  2:  ADC overflow
  case  4: break;                           // Vector  4:  ADC timing overflow
  case  6:                                  // Vector  6:  ADC12IFG0
    temp = ADC12MEM7;                       // Move results, IFG is cleared
    __bic_SR_register_on_exit(LPM4_bits);   // Exit active CPU
    break;
  case  8: break;                           // Vector  8:  ADC12IFG1
  case 10: break;                           // Vector 10:  ADC12IFG2
  case 12: break;                           // Vector 12:  ADC12IFG3
  case 14: break;                           // Vector 14:  ADC12IFG4
  case 16: break;                           // Vector 16:  ADC12IFG5
  case 18: break;                           // Vector 18:  ADC12IFG6
  case 20: break;                           // Vector 20:  ADC12IFG7
  case 22: break;                           // Vector 22:  ADC12IFG8
  case 24: break;                           // Vector 24:  ADC12IFG9
  case 26: break;                           // Vector 26:  ADC12IFG10
  case 28: break;                           // Vector 28:  ADC12IFG11
  case 30: break;                           // Vector 30:  ADC12IFG12
  case 32: break;                           // Vector 32:  ADC12IFG13
  case 34: break;                           // Vector 34:  ADC12IFG14
  default: break;
  }
}

I used the formula from the example you pointed out - and everything is working well. Thanks for all of your help.