TMP61: Can we achieve 1C accuracy using 10Bit ADC(MSP430FR2433 MCU)?

Jevant,

I was able to resolve the problem by using a 1.5V bias instead of 3.3V.  This is because the MSP430FR2433 only has a 1.5V internal reference voltage.  I have attached some Energia code which configures the device and sends the data via UART on a terminal.  See the test results below measured at ~8C.  The red line is the TMP117 used for reference and the blue line is the TMP61 after filtering and offset.  Let me know if you are able to make use of this to resolve your issue as well.

Here is the code.

/*
  AnalogReadSerial TMP6
  Reads an analog input on pin 6, prints the result to the serial monitor.
  Attach the center pin of a potentiometer to pin A3, and the outside pins to ~3V and ground.

  Hardware Required:
    MSP-EXP430F5529 LaunchPad
    TMP6 with bias resistor
    hook-up wire

  This example code is in the public domain.


*/
#include <Wire.h>
int sensorPin = A6;    // select the input pin for the potentiometer
int sensorValue = 0;
float VTEMP = 0;
float AMB_TEMP = 0;
float Meas_Temp = 0;        //
float Alpha = 0.01;       // .001<α<1, adjust as required
float Filtered_Temp = 21;        // Set a default filtered temperature value equal to the first measured value to reduce the ramp time
//float THRM_A0 =  -5.479495E+02 ;     //using TMP6131DYAR here on MSP430F5529LP
//float THRM_A1 = 7.540674E+02  ;
//float THRM_A2 =   -4.376661E+02 ;
//float THRM_A3 =   1.387438E+02  ;
//float THRM_A4 =   -1.366970E+01 ;

    float THRM_A0 =  -4.054532E+02 ;
    float THRM_A1 = 9.517609E+02  ;
    float THRM_A2 =   -7.891225E+02 ;
    float THRM_A3 =   3.701203E+02  ;
    float THRM_A4 =   2.121926E+01  ;




// the setup routine runs once when you press reset:
void setup() {
  // initialize serial communication at 115200 bps:
  Serial.begin(115200);
  Wire.begin(0);
  Wire.setTimeout(0);
  delay(1000);

  //    analogReference (DEFAULT);
      analogReference (INTERNAL1V5);
//      analogReference (INTERNAL2V5);
//      analogReference (EXTERNAL);
}

// the loop routine runs over and over again forever:
void loop() {
  // read the input on analog pin A6:
  sensorValue = analogRead(sensorPin);
  // convert to voltage
  VTEMP = ((1.5 / 1023) * sensorValue);
  //convert to temp in C
  AMB_TEMP = ((THRM_A4 * powf(VTEMP, 4)) + (THRM_A3 * powf(VTEMP, 3)) + (THRM_A2 * powf(VTEMP, 2)) + (THRM_A1 *  powf(VTEMP, 1)) + THRM_A0); // 4th order regression to get temperature

  //  Serial.print(",");
  //  Serial.println(sensorValue);
  //
//    Serial.print(",");
//    Serial.println(VTEMP, 4);

  //  Serial.print(AMB_TEMP, 4);
  //  Serial.print(",");

  // Filter
  Meas_Temp = AMB_TEMP;        // It's assumed that you have read the ADC and calculated your temperature
  Filtered_Temp = Filtered_Temp - (Alpha * (Filtered_Temp - Meas_Temp));
  Serial.print(Filtered_Temp + 0, 4);  //set offset
  Serial.print(",");

  //Read from the TMP117
//  Wire.requestFrom(72, 2);
//  while (Wire.available())
//  {
//    int Byte = Wire.read(); //reads the first Byte
//    Byte = Byte << 8; // shifts the first byte by 8 making it the high byte valuexz
//    Byte += Wire.read(); // reads the next byte and appends to the first byte
//    double tmp117_temp = Byte * .0078125; //converts the data to temp
//    Serial.println(tmp117_temp, 4); // displays the data
//   //     Serial.print(",");
//  }
//  delay(50); // delay in between reads for stability
}

/*
  AnalogReadSerial TMP6
  Reads an analog input on pin 6, prints the result to the serial monitor.
  Attach the center pin of a potentiometer to pin A6, and the outside pins to ~1.5V and ground.

  Hardware Required:
    MSP430FR2433 LaunchPad
    TMP6 with bias resistor
    hook-up wire

  This example code is in the public domain.


*/
#include <Wire.h>
int sensorPin = A6;    // select the input pin for the potentiometer
int sensorValue = 0;
float VTEMP = 0;
float AMB_TEMP = 0;
float Meas_Temp = 0;        //
float Alpha = 0.01;       // .001<α<1, adjust as required
float Filtered_Temp = 21;        // Set a default filtered temperature value equal to the first measured value to reduce the ramp time
//float THRM_A0 =  -5.479495E+02 ;     
//float THRM_A1 = 7.540674E+02  ;
//float THRM_A2 =   -4.376661E+02 ;
//float THRM_A3 =   1.387438E+02  ;
//float THRM_A4 =   -1.366970E+01 ;

    float THRM_A0 =  -4.054532E+02 ;   //using TMP6131DYAR here on MSP430FR2433LP
    float THRM_A1 = 9.517609E+02  ;
    float THRM_A2 =   -7.891225E+02 ;
    float THRM_A3 =   3.701203E+02  ;
    float THRM_A4 =   2.121926E+01  ;




// the setup routine runs once when you press reset:
void setup() {
  // initialize serial communication at 115200 bps:
  Serial.begin(115200);
  Wire.begin(0);
  Wire.setTimeout(0);
  delay(1000);

  //    analogReference (DEFAULT);
      analogReference (INTERNAL1V5);
//      analogReference (INTERNAL2V5);
//      analogReference (EXTERNAL);
}

// the loop routine runs over and over again forever:
void loop() {
  // read the input on analog pin A6:
  sensorValue = analogRead(sensorPin);
  // convert to voltage
  VTEMP = ((1.5 / 1023) * sensorValue);
  //convert to temp in C
  AMB_TEMP = ((THRM_A4 * powf(VTEMP, 4)) + (THRM_A3 * powf(VTEMP, 3)) + (THRM_A2 * powf(VTEMP, 2)) + (THRM_A1 *  powf(VTEMP, 1)) + THRM_A0); // 4th order regression to get temperature

  //  Serial.print(",");
  //  Serial.println(sensorValue);
  //
//    Serial.print(",");
//    Serial.println(VTEMP, 4);

  //  Serial.print(AMB_TEMP, 4);
  //  Serial.print(",");

  // Filter
  Meas_Temp = AMB_TEMP;        // It's assumed that you have read the ADC and calculated your temperature
  Filtered_Temp = Filtered_Temp - (Alpha * (Filtered_Temp - Meas_Temp));
  Serial.print(Filtered_Temp + 0, 4);  //set offset
  Serial.print(",");

  //Read from the TMP117
//  Wire.requestFrom(72, 2);
//  while (Wire.available())
//  {
//    int Byte = Wire.read(); //reads the first Byte
//    Byte = Byte << 8; // shifts the first byte by 8 making it the high byte valuexz
//    Byte += Wire.read(); // reads the next byte and appends to the first byte
//    double tmp117_temp = Byte * .0078125; //converts the data to temp
//    Serial.println(tmp117_temp, 4); // displays the data
//   //     Serial.print(",");
//  }
//  delay(50); // delay in between reads for stability
}