MSP430G2553: Internal temperature sensor

Hi Yehuda,

Can you please provide a minimal set of code that reproduces the issue with a description of the changes you're making in the comments?

Best regards,
Caleb Overbay

Yes, of course.

Function 1: 

long VBAT_SAMPLE()
{
long voltage = 0;
const int num_of_samp = 3;
int i;
long actual_voltage;
/*now that we have two function with ADC we need to change the channel at the entry of each function.*/

ADC10CTL0 = SREF_1 + ADC10SHT_2 + REFON + ADC10ON + ADC10IE;// + REF2_5V;

ADC10CTL1 = INCH_0; // input A0
ADC10AE0 |= 0x01; // PA.0 ADC option select
for(i = 0; i< num_of_samp; i++)
{
ADC10CTL0 |= ENC | ADC10SC; // Sampling and conversion start
delay(1);
voltage += ADC10MEM;
}
voltage = voltage/num_of_samp;
actual_voltage = 4000 - (int)(((890-voltage)/2)*10)+130; //890 is the value for 4.0V and we get a drop of about 22 every 100mV. the return of this function is in mV.

int j;
if(!(P1IN & CAP_INT.BIT))
{
if((actual_voltage<VOLTAGE_THRESHOLD) && (actual_voltage > 2000))
{
UNSET_HEATER();
for(j=0;j<LED_NUM;j++)
ControlLED(LEDS[j],ON); // turn on all LEDs
Buzzer(500); //activate the buzzer for 4000 milliseconds
for(j=0;j<LED_NUM;j++)
ControlLED(LEDS[j],OFF); // turn off all LEDs
LOW_VOLTAGE_FLAG = TRUE; //Set this flag to one so the system will know that the voltage has dropped.

Mc = Mc + Mt/10;
Mt = 0;

STATUS = STATUS_LPM3; //go to LPM3 to save power and also for start counting VD timer.
}
else
{
//LOW_VOLTAGE_FLAG = FALSE;
}
}
return actual_voltage;
ADC10CTL0 &= ~ENC;
ADC10CTL0 &= ~ADC10SC;
}

Function 2:

int SAMPLE_LIGHT_SENSOR() // sample the light sensor and return the sampled value. The calculated value is a numerical value representative of the amount of light sensed but is unitless
{
long sample = 0;
static long z = 0;
int i;
int sample_avg_num = 10;
int us;
//static long CAL_V15;
ADC10CTL0 = SREF_1 + ADC10SHT_2 + REFON + ADC10ON + ADC10IE;
ADC10CTL1 = INCH_5; // input A1
ADC10AE0 |= 0x20; // PA.5 ADC option select
for(i=0;i<sample_avg_num;i++)
{
ADC10CTL0 |= ENC + ADC10SC; // Sampling and conversion start
us=22; //wait for _____ so the sample will be accurate
while (us)
{
__delay_cycles(1); //990 for 1MHz
us--;
}
sample += ADC10MEM;
z = ADC10MEM;
}
sample = sample/sample_avg_num;
sample = (sample*(((long)(*CAL_15V)*100)/32768))/100; // dividing by 2^15 as defined in the datasheet for using the calibration values of the ADC

#ifndef DEBUG
return sample;
#else
return vr_debug;//260;
#endif
ADC10CTL0 &= ~ENC;
ADC10CTL0 &= ~ADC10SC;
}

Function 3: (with internal temperature sensor)

int Temperature_measuring()
{
//WDTCTL = WDTPW | WDTHOLD; // Stop WDT
long temp;
int num_of_sample = 5;
int i;
int us=300; //wait for _____ so the sample will be accurate

ADC10CTL1 = INCH_10 | ADC10DIV_3; // Temp Sensor ADC10CLK/4
ADC10CTL0 = SREF_1 | ADC10SHT_2 | REFON | ADC10ON | ADC10IE;
ADC10CTL0 |= ENC | ADC10SC; // Sampling and conversion start
for(i = 0; i < num_of_sample; i++)
{
us=300;
while (us)
{
__delay_cycles(1); //990 for 1MHz
us--;
}
temp = temp + ADC10MEM;
}
temp = temp/num_of_sample;
//IntDegC1= (long)(*CAL_TEMP_15V_30C);
//IntDegC2= (long)(*CAL_TEMP_15V_85C);
//IntDegC4 = (temp - IntDegC1)*(55/(IntDegC2 - IntDegC1))+30;
ADC10CTL0 &= ~ENC;
ADC10CTL0 &= ~ADC10SC;
return (temp);
}

The problem occurs only if the “ADC10CTL0 |= ENC + ADC10SC” is used in function 1 and 2. If I put this line under comment in functions 1 and two, the output of the temperature function is OK.