diff --git a/src/math/p_sincos.c b/src/math/p_sincos.c index ffb121f..c4b7084 100644 --- a/src/math/p_sincos.c +++ b/src/math/p_sincos.c @@ -1,4 +1,88 @@ #include +#include +#include + +#define SIN_COS_ITERATIONS 17 + +//Cordic in 32 bit signed fixed point math +//Function is valid for arguments in range -pi/2 -- pi/2 +//for values pi/2--pi: value = half_pi-(theta-half_pi) and similarly for values -pi---pi/2 +// +// 1.0 = 1073741824 +// 1/k = 0.6072529350088812561694 +// pi = 3.1415926535897932384626 +//Constants +#define cordic_1K 0x26DD3B6A +#define half_pi 0x6487ED51 +#define MUL 1073741824.000000 +#define MUL_RECIP 1.0/MUL +#define CORDIC_NTAB 32 +int cordic_ctab[] = { 0x3243F6A8, 0x1DAC6705, 0x0FADBAFC, 0x07F56EA6, + 0x03FEAB76, 0x01FFD55B, 0x00FFFAAA, 0x007FFF55, 0x003FFFEA, 0x001FFFFD, + 0x000FFFFF, 0x0007FFFF, 0x0003FFFF, 0x0001FFFF, 0x0000FFFF, 0x00007FFF, + 0x00003FFF, 0x00001FFF, 0x00000FFF, 0x000007FF, 0x000003FF, 0x000001FF, + 0x000000FF, 0x0000007F, 0x0000003F, 0x0000001F, 0x0000000F, 0x00000008, + 0x00000004, 0x00000002, 0x00000001, 0x00000000, }; + +void cordic(int theta, int *s, int *c, int n) { + int k, d, tx, ty, tz; + int x = cordic_1K, y = 0, z = theta; + n = (n > CORDIC_NTAB) ? CORDIC_NTAB : n; + for (k = 0; k < n; ++k) { + d = z >> 31; + //get sign. for other architectures, you might want to use the more portable version + //d = z>=0 ? 0 : -1; + tx = x - (((y >> k) ^ d) - d); + ty = y + (((x >> k) ^ d) - d); + tz = z - ((cordic_ctab[k] ^ d) - d); + x = tx; + y = ty; + z = tz; + } + *c = x; + *s = y; +} + +float normalizeRadiansToPlusMinusM_PI(float radians) { + unsigned int *radiansBits = (unsigned int *)&radians; + unsigned int signBit = *radiansBits & 0x80000000u; + *radiansBits = *radiansBits ^ signBit; //remove any negative bit + + int revolutions = (int) (radians * M_1_PI) + 1; + revolutions = revolutions >> 1; // div 2 + + radians = radians - revolutions * (2 * M_PI); //subtract whole revolutions, now in range [-pi..pi] + + *radiansBits = *radiansBits ^ signBit; //if was negative, flip negative bit + return radians; +} + +int radiansToPlusMinusM_PI_2(float *radians) { + int flip = 0; + *radians = normalizeRadiansToPlusMinusM_PI(*radians); + + if (*radians < -M_PI_2 || *radians > M_PI_2) { + if (*radians < 0) { + *radians += M_PI; + } else { + *radians -= M_PI; + } + flip = 1; //flip the sign for second or third quadrant + } + return flip; +} + +void cordicF(float theta, float *s, float *c, int n) { + int sint, cint; + int flip = radiansToPlusMinusM_PI_2(&theta); + cordic(theta * MUL, &sint, &cint, n); + *s = sint * MUL_RECIP; + *c = cint * MUL_RECIP; + if (flip) { + *s = -*s; + *c = -*c; + } +} /** * @@ -21,6 +105,11 @@ void p_sincos_f32(const float *a, float *c, float *z, int n) { - p_sin_f32(a, c, n); - p_cos_f32(a, z, n); + int i; + for (i = 0; i < n; i++) { + const float angle = a[i]; + float *pcos = z + i; + float *psin = c + i; + cordicF(angle, psin, pcos, SIN_COS_ITERATIONS); + } }