cordic_C_.rar_cordic C_cordic c 实现_cordic c++_cordic cos_计算sin C

/**************************************************************************** * * Name: cordic.c * * Synopsis: Demonstration of the CORDIC algorithm * * Description: * * This module demonstrates the CORDIC algorithm, which can calculate the * trigonometric functions of sin, cos, magnitude and phase using * multiplying factors which are powers of two. Therefore, the multiplies * can be implemented in hardware as shift/adds. (Since C doesn't let you * shift "doubles", the shift/add multiplies appear here as literal * multiplies, but you get the idea.) * * This module is designed as an "object" since it requires a data table * which must be filled once prior to use. Call the "cordic_construct" * function first to allocate and build the table, then call the CORDIC * functions, and finally call "cordic_destruct" to free the table. * * This modules isn't highly "bulletproofed" and also is not completely * optimum because it is intended primarily to demonstrate the algorithm. * * Copyright 1999 Grant R. Griffin * * The Wide Open License (WOL) * * Permission to use, copy, modify, distribute and sell this software and its * documentation for any purpose is hereby granted without fee, provided that * the above copyright notice and this license appear in all source copies. * THIS SOFTWARE IS PROVIDED "AS IS" WITHOUT EXPRESS OR IMPLIED WARRANTY OF * ANY KIND. See http://www.dspguru.com/wol.htm for more information. * *****************************************************************************/ #include <stdlib.h> #include <math.h> #include "cordic.h" #define INVALID_K -1 typedef struct tagCORDIC_TABLE { double K; double phase_rads; } CORDIC_TABLE; CORDIC_TABLE *mp_cordic_table = NULL; int m_max_L = INVALID_K; double m_mag_scale; /****************************************************************************/ int cordic_construct(int max_L) { double K, dummy; int L; cordic_destruct(); /* free previous table, if any */ mp_cordic_table = (CORDIC_TABLE *) calloc(max_L + 1, sizeof(CORDIC_TABLE)); if (!mp_cordic_table) { return 0; /* failed to calloc table */ } K = 1.0f; for (L = 0; L <= max_L; L++) { mp_cordic_table[L].K = K; mp_cordic_table[L].phase_rads = (double) atan(K); K *= 0.5f; } m_max_L = max_L; /* get m_mag_scale by getting the cordic magnitude with m_mag_scale = 1.0 */ m_mag_scale = 1.0; cordic_get_mag_phase(1.0, 0.0, &m_mag_scale, &dummy); m_mag_scale = 1.0 / m_mag_scale; return 1; /* success */ } /****************************************************************************/ void cordic_destruct(void) { free(mp_cordic_table); mp_cordic_table = NULL; m_max_L = INVALID_K; } /****************************************************************************/ void cordic_get_mag_phase(double I, double Q, double *p_mag, double *p_phase_rads) { int L; double tmp_I, K, phase_rads, acc_phase_rads; if (I < 0) { /* rotate by an initial +/- 90 degrees */ tmp_I = I; if (Q > 0.0f) { I = Q; /* subtract 90 degrees */ Q = -tmp_I; acc_phase_rads = -HALF_PI; } else { I = -Q; /* add 90 degrees */ Q = tmp_I; acc_phase_rads = HALF_PI; } } else { acc_phase_rads = 0.0; } /* rotate using "1 + jK" factors */ for (L = 0; L <= m_max_L; L++) { K = mp_cordic_table[L].K; phase_rads = mp_cordic_table[L].phase_rads; tmp_I = I; if (Q >= 0.0) { /* phase is positive: do negative roation */ I += Q * K; Q -= tmp_I * K; acc_phase_rads -= phase_rads; } else { /* phase is negative: do positive rotation */ I -= Q * K; Q += tmp_I * K; acc_phase_rads += phase_rads; } } *p_phase_rads = -acc_phase_rads; *p_mag = I * m_mag_scale; } /****************************************************************************/ void cordic_get_cos_sin(double desired_phase_rads, double *p_cos, double *p_sin) { double I, Q, tmp_I; double acc_phase_rads, phase_rads, K; int L; /* start with +90, -90, or 0 degrees */ if (desired_phase_rads > HALF_PI) { I = 0.0; Q = 1.0; acc_phase_rads = HALF_PI; } else if (desired_phase_rads < -HALF_PI) { I = 0.0; Q = -1.0; acc_phase_rads = -HALF_PI; } else { I = 1.0; Q = 0.0; acc_phase_rads = 0.0; } /* rotate using "1 + jK" factors */ for (L = 0; L <= m_max_L; L++) { K = mp_cordic_table[L].K; phase_rads = mp_cordic_table[L].phase_rads; tmp_I = I; if (desired_phase_rads - acc_phase_rads < 0.0) { /* do negative roation */ I += Q * K; Q -= tmp_I * K; acc_phase_rads -= phase_rads; } else { /* do positive rotation */ I -= Q * K; Q += tmp_I * K; acc_phase_rads += phase_rads; } } *p_cos = I * m_mag_scale; *p_sin = Q * m_mag_scale; }