How to interpret the result from analogRead

[pine 140]

In the classical temperature reading example in CCS, the following code is used for reading and calculation:

 

    ADC10CTL0 |= ENC + ADC10SC;             // Sampling and conversion start
   // oC = ((A10/1024)*1500mV)-986mV)*1/3.55mV = A10*423/1024 - 278
   temp = ADC10MEM;
   IntDegC = ((temp - 673) * 423) / 1024;

 

While in the sample code from Energia, the following line gave a substantially different forumla.. so I'm wondering there are differences between the two analog values read?

 

    values[j] = ((uint32_t)analogRead(TEMPSENSOR)*27069 - 18169625) *10 >> 16;

[energia 485]

Rei Vilo would have to explain why he did it this way since he wrote the code. Probably to get more precision.

With that said, you can use the formula that is used in the CCS example without a problem.

[gwdeveloper 275]

There are more accurate methods to calculate the temperature than what TI originally supplied...

 

http://www.43oh.com/forum/viewtopic.php?f=10&t=2474

http://www.43oh.com/forum/viewtopic.php?f=10&t=2549

[Rei Vilo 695]

The formula I used came from the original sketch.

 

I checked it against the seminal post Using the internal temperature sensor from opossum.

 

Thank you, opossum, for the detailed formula!