Calibration routine for ADS7843

ADS7843 Calibrate function

void ADS7843_Calibrate(void)
{
	static Coordinate *Pos;
	uint16_t MatriceA[3][3] = {{1,1,1},{1,1,1},{1,1,1}};			// MatriceA for values of ADC ADS7843					   								   
	uint8_t i,j;								// Inserts itself into a matrix
	uint32_t detA;								// determinant matriceA
	int32_t transA[3][3];							// transpose matriceA
	float invA[3][3];							// Invert MatriceA
	float pom;								// to save 1/detA

	// Displays 3 points and their coordinates are obtained

	for(i=0;i<3;i++)

	{
		// Caibration Point P1 shown on the LCD Matrices X,Y contain the coordinates of P1
		// correct for 16 bit resolution

		LCD_DrawCalibPoint(MatriceX[i] - 8, MatriceY[i] - 8);
		while(GPIO_ReadInputDataBit(GPIOB,GPIO_Pin_15));		// hold on to confirm position
		Pos = ADS7843_Read();
		while(!EXTI_GetITStatus(EXTI_Line6));		                // wait till stopped pressing touchscreenu
		MatriceA[i][0] = Pos->x;
		MatriceA[i][1] = Pos->y;
		Delay(0x9FFFFF);			                        // time between showing cailbartion points
	}

	// determinant marice A

	detA = (MatriceA[0][0]*((MatriceA[1][1]*MatriceA[2][2])-(MatriceA[1][2]*MatriceA[2][1]))) +
	       (MatriceA[0][1]*((MatriceA[1][2]*MatriceA[2][0])-(MatriceA[2][2]*MatriceA[1][0]))) +
	       (MatriceA[0][2]*((MatriceA[1][0]*MatriceA[2][1])-(MatriceA[1][1]*MatriceA[2][0])));


	// z matice A urobí transponovu maticu  a vloži ju do transA
	//	            			     | a b c |^-1		             | A B C |^ T
	// MatriceA^-1 = 1/det(MatriceA)*| d e f |     = 1/det(MatriceA)*| D E F |	 =
	//             				     | g h k |		                 | G H K |
	// 					  | A D G |
	// = 1/det(MatriceA)* | B E H | = 1/det(MatriceA)* transA
	//					  | C F K |
	//
	// a(0,0) b(0,1) c(0,2) d(1,0) e(1,1) f(1,2) g(2,0) h(2,1) k(2,2)
	//
	// A = (e*k - f*h)	    D = (h*c - b*k)		G = (b*f - e*c)
	// B = (f*g - d*k)		E = (a*k - g*c)	    H = (c*d - a*f)
	// C = (d*h - e*g)	    F = (g*b - a*h)		K = (a*e - b*d)
	//
	// Transposed MatriceA
        
	transA[0][0] = (MatriceA[1][1] * MatriceA[2][2]) - (MatriceA[1][2] * MatriceA[2][1]);		// A
	transA[1][0] = (MatriceA[1][2] * MatriceA[2][0]) - (MatriceA[1][0] * MatriceA[2][2]);		// B
	transA[2][0] = (MatriceA[1][0] * MatriceA[2][1]) - (MatriceA[1][1] * MatriceA[2][0]);		// C

	transA[0][1] = (MatriceA[2][1] * MatriceA[0][2]) - (MatriceA[0][1] * MatriceA[2][2]);		// D
	transA[1][1] = (MatriceA[0][0] * MatriceA[2][2]) - (MatriceA[2][0] * MatriceA[0][2]);		// E
	transA[2][1] = (MatriceA[2][0] * MatriceA[0][1]) - (MatriceA[0][0] * MatriceA[2][1]);		// F

	transA[0][2] = (MatriceA[0][1] * MatriceA[1][2]) - (MatriceA[1][1] * MatriceA[0][2]);		// G
	transA[1][2] = (MatriceA[0][2] * MatriceA[1][0]) - (MatriceA[0][0] * MatriceA[1][2]);		// H
	transA[2][2] = (MatriceA[0][0] * MatriceA[1][1]) - (MatriceA[0][1] * MatriceA[1][0]);		// K

	// Inverse matrix of MatriceA
	 //MatriceA^-1 = (1/detA) * transA
        
	pom = 1/((float)detA);

	for(i=0;i<3;i++)
	{
		for(j=0;j<3;j++)
		{
			invA[i][j] = pom * ((float)transA[i][j]);
		}
	}

	// |aX|			 |X1|	X1, X2, X3 Are X Coordinates of calibration points on the LCD
	// |bX| = A^-1 * |X2|
	// |dX|			 |X3|
	aX = invA[0][0]*(float)MatriceX[0] + invA[0][1]*(float)MatriceX[1] + invA[0][2]*(float)MatriceX[2];
	bX = invA[1][0]*(float)MatriceX[0] + invA[1][1]*(float)MatriceX[1] + invA[1][2]*(float)MatriceX[2];
	dX = invA[2][0]*(float)MatriceX[0] + invA[2][1]*(float)MatriceX[1] + invA[2][2]*(float)MatriceX[2];

	// |aY|			 |Y1|	Y1, Y2, Y3 Are Y Coordinates of calibration points on the LCD
	// |bY| = A^-1 * |Y2|
	// |dY|			 |Y3|
	aY = invA[0][0]*(float)MatriceY[0] + invA[0][1]*(float)MatriceY[1] + invA[0][2]*(float)MatriceY[2];
	bY = invA[1][0]*(float)MatriceY[0] + invA[1][1]*(float)MatriceY[1] + invA[1][2]*(float)MatriceY[2];
	dY = invA[2][0]*(float)MatriceY[0] + invA[2][1]*(float)MatriceY[1] + invA[2][2]*(float)MatriceY[2];
}