intsincordic.c

是codic算法实现Sin的浮点C程序

#include "headDefine.h"

int intSinCordic(unsigned long theta) {
	
	int i;  				// for iteration
	int N = 14;  			// loop times // NTSC:N=7
	
	// 415097064 = round(0.607253 * 256) = 155
	int X[21] = {0};	// 11 = N + 1 432 142
	int Y[21] = {0};
	int result = 0;			// the return result
	int precision = 4;		// the pricision of the radian 36 -> 0.1

	int thetaQuadrant = 0;	// the quadrant of theta
	int thetaFlag = 0;		// 1 means theta1:[PI/4, PI/2]
	int S;					// 
	//int quotient;
	// 
	int thetaTable[17] = {51472,   30386, 16055,   8150, 4091,  2047, 1024,  512, 256,
						  128,    64,    32,    16,      8,     4,    2,   1};
	/*int thetaTable[30] = {
		1686629713,	995675659,	526087673,	267050317,	134043374,	67087031,
		33551702,	16776875,	8388565,	4194299,	2097151,	1048576,
		524288,		262144,		131072,		65536,		32768,		16384,
		8192,	4096,	2048,	1024,  512,  256,  128,  64,  32,  16,	8,	4};*/



	long theta1 = (theta >> 15);	// BACK_BIT = 23
	
	// get the (theta1 % (2 * SHORT_PI_CORDIC)), [0, 2*SHORT_PI_CORDIC]
	//quotient = floor(theta1 / (2 * SHORT_PI_CORDIC));
	//theta1 = theta1 - 2 * SHORT_PI_CORDIC * quotient;
	
	// turn to the range: [-SHORT_PI_CORDIC, SHORT_PI_CORDIC]
	//if (theta1 > SHORT_PI_CORDIC && theta1 <= 2 * SHORT_PI_CORDIC) {
	//	theta1 = theta1 - 2 * SHORT_PI_CORDIC;
	//}

	// judge the quadrant of theta, and transfer theta1 to the first quadrant
    if (theta1 >= 0 && theta1 <= SHORT_PI_CORDIC / 2) {					// 第一象限
        //theta1 = theta1;
        thetaQuadrant = 1;
	}
    else if (theta1 > SHORT_PI_CORDIC / 2 && theta1 <= SHORT_PI_CORDIC) {			// 第二象限
        theta1 = SHORT_PI_CORDIC - theta1;
        thetaQuadrant = 2;
	}
	else if (theta1 >= SHORT_PI_CORDIC && theta1 < SHORT_PI_CORDIC / 2 * 3) {		// 第三象限
        theta1 = theta1 - SHORT_PI_CORDIC;
        thetaQuadrant = 3;
	}
	else if (theta1 >= SHORT_PI_CORDIC / 2 * 3 && theta1 < 2 * SHORT_PI_CORDIC) {	// 第四象限
        theta1 = 2 * SHORT_PI_CORDIC - theta1;
        thetaQuadrant = 4;
	}
	
	// judge if theta1 is belongs: [PI/4, PI/2], use sin(theta1) = cos(PI/2 - theta1)
	if (theta1 > SHORT_PI_CORDIC / 3 && theta1 <= SHORT_PI_CORDIC / 2) {
		theta1 = SHORT_PI_CORDIC / 2 - theta1;
		thetaFlag = 1;
		X[0] = 146;   // 142
	}
	else if (theta1 >= 0 && theta1 <= SHORT_PI_CORDIC / 3) {
		thetaFlag = 0;
		X[0] = 432;  // 432
	}


	// SHORT_PI_CORDIC(65536) / 180 = 364表示1度
	if (theta1 == 0 || (theta1 >= 10905 && theta1 <= 10941) || (theta1 >= 16366 && theta1 <= 16402) //) {
		|| (theta1 >= 21817 && theta1 <= 21863)){ // || theta1 == SHORT_PI_CORDIC / 2) {
		if (theta1 == 0) {
			if (thetaFlag == 1)
				result = 256;
			else
				result = 0;
		}
		else if (theta1 >= 10887 && theta1 <= 10959) { // 65536 / 6 = 10923 偏移0.1度的范围:[PI/6-0.1, PI/6+0.1]
			if (thetaFlag == 1)
				result = 222;
			else
				result = 128;
		}
		else if (theta1 >= 16348 && theta1 <= 16420) // 16384 偏移0.1度的范围:[PI/4-0.1, PI/4+0.1]
			result = 181;
		else if (theta1 >= 21809 && theta1 <= 21881) // 65536 / 3 = 21845 偏移0.1度的范围:[PI/3-0.1, PI/3+0.1]
			result = 222;
		/*else if (theta1 == SHORT_PI_CORDIC / 2)
			result = 256;*/

		if (thetaQuadrant == 1 || thetaQuadrant == 2)
			result = result;
		else if (thetaQuadrant == 3 || thetaQuadrant == 4)
			result = -result;
	
	}
	else {
		// main iterations
		//theta1 = theta1;
		for (i = 0; i < N; i++) {
			// get the sign of S 
			// that is the clockwise or anticlockwise rotation
			if (theta1 > precision)
				S = 1;
			else if (theta1 < -precision)
				S = -1;
			else {
				break;
			}
			
			X[i + 1] = X[i] - S * (Y[i] >> i);
			Y[i + 1] = Y[i] + S * (X[i] >> i);
			theta1 = theta1 - S * thetaTable[i];
		}
		
		if (thetaFlag == 1) {
			result = X[i];  // cos
		}
		else result = Y[i]; // sin
		
		if (thetaQuadrant == 1 || thetaQuadrant == 2)
			result = result;
		else if (thetaQuadrant == 3 || thetaQuadrant == 4)
			result = -result;
	
	}
	
	//result = result / 256;
	return(result);
}