//*****************************************************************************
//*****************************************************************************
//  FILENAME:  CMX_FTTHERM.c
//   Version: 1.1, Updated on 2008/6/23 at 14:7:12, Updated on 2007/05/18 at 22:47:55
//  
//
//  DESCRIPTION: 
//    This container Driver gets the voltage values from the thermistor circuit (by two MVolts subdrivers), calculates and returns the value of temperature.
//
//-----------------------------------------------------------------------------
//      Copyright (c) Cypress MicroSystems 2005. All Rights Reserved.
//*****************************************************************************
//*****************************************************************************

#include "CMX.h"
#include "CMX_FTTHERM.h"

#define	MIN		-101
#define	MAX		551	
#define COUNT_VALUES    23

const int arTherm[2][COUNT_VALUES] = 
{   
   {2301, 2505, 2725, 2960, 3211, 3477, 3757, 4051, 4358, 4675, 5000, 5331, 5664, 5998, 6328, 6652, 6967, 7269, 7557, 7829, 8083, 8317,  8462},
   {5500, 5200, 4900, 4600, 4300, 4000, 3700, 3400, 3100, 2800, 2500, 2200, 1900, 1600, 1300, 1000,  700,  400,  100, -200, -500, -800, -1000}   // array of temperature values (in hundredths of a deg C)
//     1           3           5           7           9          11          13          15          17          19          21           23
};

//-----------------------------------------------------------------------------
//  FUNCTION NAME: FTTHERM_Instantiate(const CMX_NFTHERM_ParameterBlock * thisBLK)
//
//  DESCRIPTION:  
//    This function doesn't do anything at this time, but is placed here
//    for forward compatibility.
//
//-----------------------------------------------------------------------------
//
//  ARGUMENTS: 
//    thisBLK  => Pointer to ParameterBlock for this instance.
//
//  RETURNS: None
//
//  SIDE EFFECTS: 
//
//  THEORY of OPERATION or PROCEDURE: 
//
//-----------------------------------------------------------------------------

void CMX_FTTHERM_Instantiate(const CMX_FTTHERM_ParameterBlock * thisBLK)
{
   // Blank function  
}

//-----------------------------------------------------------------------------
//  FUNCTION NAME: FTTHERM_GetValue(const CMX_NFTHERM_ParameterBlock * thisBLK)
//
//  DESCRIPTION:  
//    This function gets the Vexc and Vthermistor voltages (from MVOLTS subdrivers) and returns the calculated value of temperature.
//
//-----------------------------------------------------------------------------
//
//  ARGUMENTS: 
//    thisBLK  => Pointer to ParameterBlock for this instance.
//
//  RETURNS: 
//	int lVtherm => signed integer value of temperature.
//
//  SIDE EFFECTS: 
//
//  THEORY of OPERATION or PROCEDURE: This function gets the Vexc and Vthermistor voltages, calculates it's relation, and calculates the value of temperature  by the method of piece-linear approximation.
//
//-----------------------------------------------------------------------------

int CMX_FTTHERM_GetValue(const CMX_FTTHERM_ParameterBlock * thisBLK)
{
	BYTE bPointIndex;
	long lVtherm;
	int ivalue1,ivalue2,itemp1,itemp2;

	ivalue1 = CMX_mVolts_GetValue(thisBLK->ptrEXC);
	lVtherm = CMX_mVolts_GetValue(thisBLK->ptrTHERM);

	lVtherm *= 10000;
	lVtherm /= ivalue1;
	
	if ((int)lVtherm < arTherm[0][0])
	{
		// The voltage ratio is too low, so the temperature is greater than what can be measured                
		lVtherm = MAX;
	}
	else if((int)lVtherm > arTherm[0][COUNT_VALUES-1])
	{
		// The voltage ratio is too high, so the temperature is less than what can be measured.
		lVtherm = MIN; 
	}
	else 
	{  
		// Scan through the voltage ratio values in the piecewise linear curve fit data to find
                // the appropriate line to interpolate                
		for(bPointIndex = 0; bPointIndex < (COUNT_VALUES-2); bPointIndex++) 
		{																			
			if (lVtherm < arTherm[0][bPointIndex+1])  break;
		}
		
		// Retrieve the voltage ratios for interpolation
		ivalue1 = arTherm[0][bPointIndex];
		ivalue2 = arTherm[0][bPointIndex + 1];

                // Retrieve the temperatures for interpolation
		itemp1 = arTherm[1][bPointIndex];
		itemp2 = arTherm[1][bPointIndex + 1];


		// Interpolate to find the temperature in hundredths of a deg C
		lVtherm = (((long) ivalue2 - lVtherm) * (itemp1 - itemp2)) / (ivalue2 - ivalue1) + itemp2;

                // Divide the result by 10 in order to get the temperature in tenths of a deg C.                     
                // Round to the nearest tenth rather than truncating
         
                // First, get the temperature value as an integer
                ivalue1 = lVtherm;
         
                // Next, get the sign and absolute value of the temperature
                if (ivalue1 < 0)
                {               
                   bPointIndex = 1; 
                   ivalue1 = 0 - ivalue1;
                }
                else
                {
                   bPointIndex = 0;
                }

                // Calculate the truncated form
                ivalue2 = ivalue1 / 10;  

                // Multiply the truncated form by 10 and add 5
                // If the result is less than or equal to the original undivided number, then the 
                // Truncated value must be incremented by 1.
                if ((ivalue2 * 10 + 5) <= ivalue1)
                {
                   ivalue2++;
                }
                 
                
                // Change the sign to negative if necessary               
                if (bPointIndex)
                {
                   ivalue2 = 0 - ivalue2;
                }

                
                // Store the temperature to the return value
                lVtherm = ivalue2;
	}
	
	return (int) lVtherm;
}