- //Cordic in 16 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 = 16384
- // 1/k = 0.6072529350088812561694
- // pi = 3.1415926536897932384626
- //Constants
- #define cordic_1K 0x000026DD
- #define half_pi 0x00006487
- #define MUL 16384.000000
- #define CORDIC_NTAB 16
- int cordic_ctab [] = {0x00003243, 0x00001DAC, 0x00000FAD, 0x000007F5, 0x000003FE, 0x000001FF, 0x000000FF, 0x0000007F, 0x0000003F, 0x0000001F, 0x0000000F, 0x00000007, 0x00000003, 0x00000001, 0x00000000, 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>>15;
- //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;
- }
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