MSP430FR6989: Constant voltage reference for NTC sensor

Hello,

I'm use Energia IDE.I want a static Vref constant internal voltage for NTC and NTC working on coin cell.

I refer link : energia.nu/.../. But on physical P1.1 pin didn't get any reference voltages.

So,How could I generate Internal reference and check physically on reference pin P1.1(Vref+) ?

and Internal reference means it generate internal reference for ADC or we can check voltage physically on respective pin P1.1? Please clarify this confusion.

Thank you.

Hi PRATIK

For the GPIO configuration you can refer to the datasheet of msp430fr5989 (www.ti.com/.../msp430fr6989.pdf) on page 96. We can see, when we want to output the vref+ we should configure DIR to 1 and SEL1 to 1.
And we should use" while(!(REFCTL0 & REFGENRDY)); " // Wait for reference generator to settle

Hi Gary,

Thanks for responce.

Now, on pin P1.1 I got a 1.19V through code part but I got an one issue here :

void Vref_ON()

{

while(REFCTL0 & REFGENBUSY);                                     // If ref generator busy, WAIT

REFCTL0 |= REFVSEL_0 + REFON + REFOUT;             // Enable internal 1.2V reference

while(!(REFCTL0 & REFGENRDY));            // Wait for reference generator

                                                                               // to settle

}

void Vref_Off()

{

REFCTL0=1;

}

void setup()

{

Vref_ON();

Serial.begin(9600);

}

void loop()

{

 // int val = analogRead(A11);    //**** When comment this portion then on P1.1 Vref+  get voltage (1.19V), uncomment then get voltage 0V ****

 Serial.println(val);

delay(500);

}

Please mention above comment and code.

Why this issue happen ?

Regards,

Pratik

Hi Pratik

How do you configured the ADC? What's the operation in the function of "analogRead"?

Gary

I am generate +Vref voltage from P1.1(As per MSP430FR6989 launchpad).

and applied +Vref in NTC and measure ADC value on A11 pin.

Thanks & Regards,

Pratik

Does the software problem solved now?

No,Still not solve the issue but here I am try some modifications:

#define MY_INTERNAL2V0 (ADC12VRSEL_1 | REFON | REFVSEL_0 | REFOUT)

Same issue happen, without RFCTL0 and With analogread() can not get 1.19V on physical pin.

#define MY_INTERNAL2V0 (REFCTL0|=ADC12VRSEL_1 | REFON | REFVSEL_0 | REFOUT) // Here generate 1.19V but with analogread() not generate.

I also did modification in wiring_analog.c and change #define REF_MAP(x) (x & 0x31) to #define REF_MAP(x) (x & 0x33).

Please suggest me alternative of analogread() function using registers of MSP430FR6989.

Thank you.

Hi
What's the operation in the analogread() function?

Hello Gary,

 Consider MSP430FR6989 launchapad. pin P1.1(+Vref) and P9.3 (A11) 

#define MY_INTERNAL2V0 (REFCTL0|= ADC12VRSEL_1 | REFON | REFVSEL_0 | REFOUT)  //<--- Without REFCTL0 not generate 1.2V
#define ANALOG_RES 12

void setup()
{
  analogReadResolution(ANALOG_RES);
  analogReference(MY_INTERNAL2V0);
  Serial.begin(115200);
}
void loop()
{
  int val = analogRead(A11);  //<--- This function is responsible for this issue.
  /* 
   * Note that the default resolution for the FR6989 is 12 bit. 
   * This can be changed with analogReadResolution(resolution in bits)
   */
  
  float voltage = val * (1.2 / (1 << ANALOG_RES));
  Serial.print(voltage * 1000);
  Serial.println(" mV");
  delay(500);
}

Regards,

Pratik

Hi
I can't find the define of analogRead() function in the code you have upload above. Can you show me that?

Hello Gary,

P1.1(+Vref) external and P9.3(A11) mention in MSP430FR6989.

Please look below Energia code snipet :

#define MY_INTERNAL2V0 (REFCTL0|= ADC12VRSEL_1 | REFON | REFVSEL_0 | REFOUT)  //<--- Without REFCTL0 not generate 1.2V
#define ANALOG_RES 12

void setup()
{
  analogReadResolution(ANALOG_RES);
  analogReference(MY_INTERNAL2V0);
  Serial.begin(115200);
}
void loop()
{
  int val = analogRead(A11);  //<--- This function is responsible for this issue.
  /* 
   * Note that the default resolution for the FR6989 is 12 bit. 
   * This can be changed with analogReadResolution(resolution in bits)
   */
  
  float voltage = val * (1.2 / (1 << ANALOG_RES));
  Serial.print(voltage * 1000);
  Serial.println(" mV");
  delay(500);
}

Please mention above comments.

If possible please suggest me sample code logic with respect to Register of MSP430FR6989.

Thank you.

Regards,

Pratik

Hi Pratik

So far, you can out put the 1.2 v voltage normally now? And what's the problem of your logic now? What's the logic you want to change?

Hello,

I already mention in above code comment.

I sucessfully get 1.2v using Vref+ on pin.

I have a one issue only if I'm call analogread() in void loop() . Then on Vref+ I got a 0v.

So,Please suggest me alternative of analogread() like using Register.

Regards,
Pratik

Hi

The function analogread() is API from the TI's LIB? I have not used the function before. You can just read the ADC result from the ADC12MEM register if you have configured the ADC properly before.

Gary

Hi

What's the reference voltage for the ADC? you can try use VCC as the reference voltage for ADC.

Gary

Hello Gary,

My MCU working on coin cell and it will provide 3.3V.

But coin cell will be consuming voltage.

So,I need a constant reference voltage for NTC.

Should VCC change according to coin cell voltage if I try VCC as the reference voltage ? 

Thank you.

Regards,

Pratik

Hi Pratik

I just want to verify whether the use of internal reference voltage will affect the external one.

Gary

Hi Pratik

If you can't offer the operation code about analogread(), I will close this thread fisrt. If you have even more question you can open a new post.
Thanks
Gary