[SOLVED] Problem converting ADC value using Steinhart-Hart equation

[qbone]

Hey guys.
I am trying to build a thermostat for a project, and I wanna calculate the temperature using Steinhart equation, and getting the ADC value from a voltage divider made from a 10k Thermister and a 10k 1% resistor.

I read the ADC value just fine, but the equation doesn't work.
It worked when I was playing with Arduino, so there might be some problem I havent thought of.
Here is my code:

#include <16F886.h>
#device ADC=10
#fuses INTRC_IO,NOWDT,NOLVP,NOPUT,NOMCLR,NOBROWNOUT,NOCPD,NOIESO,NOFCMEN,NOWRT,BORV21
#use delay(internal=4000000)
#use rs232(baud=57600,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=8)

#include <math.h>

long Thermister(long RawADC);

void init()
{
	setup_timer_0(T0_INTERNAL); 
	setup_timer_1(T1_DISABLED); 
	setup_timer_2(T2_DISABLED,0,1); 
	setup_comparator(NC_NC_NC_NC);

}

void main()
{
	setup_adc_ports(sAN0); 
	setup_adc(ADC_CLOCK_INTERNAL); 
	set_adc_channel(0);

	long temp;
	long value;

	while(true) {
		value = read_adc();	
		temp = Thermister(value);
		printf("A/D value: %Ld = %Ld\n\r", value, temp);
		delay_ms(500);
	}
}

long Thermister(long RawADC) //Steinhart-Hart Equation
{
	long Temp;
	Temp = log(((10240000/RawADC) - 10000)); //1024 = ADC Resolution, 10000 = 10kohm Resistor
	Temp = 1 / (0.001129148 + (0.000234125 * Temp) + (0.0000000876741 * Temp * Temp * Temp)); //Steinhart Equation
	Temp = Temp - 273.15; // Convert Kelvin to Celcius
	
	return Temp;
}

Any help would be greatly appreciated

 

[qbone]

oh, maybe it helps to understand the code if I say I am programming in MPLAB v8.85 using the CCS C Compiler and library

After hours and hours of searching the web I may have found something, but I dunno if it will work, but don't have chance of testing it till Saturday or so.
It might be the datatypes causing the issues.

The issue I am seeing is that when I heat up the thermistor I get constant output of 54, when its rooms temperature I get constant 29 untill I reach about 15 or lower, then I get constant 7.
Maybe it will help changing all datatypes to float, as my original had the datatype double (arduino code).

This is what I am gonna try

float value;
float temp;

value = (float)read_adc();	
temp = Thermister(value);

float Thermister(float RawADC) //Steinhart-Hart Equation
{
	float Temp;
	Temp = log(((10240000/RawADC) - 10000)); //1024 = ADC Resolution, 10000 = 10kohm Resistor
	Temp = 1 / (0.001129148 + (0.000234125 * Temp) + (0.0000000876741 * Temp * Temp * Temp)); //Steinhart Equation
	Temp = Temp - 273.15; // Convert Kelvin to Celcius
	
	return Temp;
}

You are all still very welcome to comment and come with pointers to wether this might work or not

 

[qbone]

I have solved it on my own.
The problem was with the datatypes, when I changed it all to float everything worked out as planned.