trigonometry.c File Reference

Macros
#define	ARCTAN_APPROX(y, x)   (-y * (47 * y - 182 * x) / 3 / x / x)

Functions
int16_t	getSin1024 (int16_t degree)
int16_t	getCos1024 (int16_t degree)
int32_t	getTan1024 (int16_t degree)
int32_t	cordicAtan2 (int32_t x, int32_t y)
	CORDIC approximation of arctan.
int16_t	getAtan2 (int32_t y, int32_t x)
	Calculate the angle of the line from the origin to (x, y), in degrees.

Variables
const int16_t	sin1024 [91]
const uint16_t	tan1024 [91]

Macro Definition Documentation

ARCTAN_APPROX

#define ARCTAN_APPROX	(		y,
			x )   (-y * (47 * y - 182 * x) / 3 / x / x)

Approximates arctan(y / x) to within 1 degree, but only when 0 <= (y / x) <= 1 Modified from https://math.stackexchange.com/a/1098585 to fit the format of your numbers.

Function Documentation

getSin1024()

int16_t getSin1024

(

int16_t

degree

)

Integer sine function

Parameters

degree

The degree, between 0 and 359

Returns

The sine of the degree, between -1024 and 1024

getCos1024()

int16_t getCos1024

(

int16_t

degree

)

Integer cosine function

Parameters

degree

The degree, between 0 and 359

Returns

The cosine of the degree, between -1024 and 1024

getTan1024()

int32_t getTan1024

(

int16_t

degree

)

Integer tangent function

Parameters

degree

The degree, between 0 and 359

Returns

The tangent of the degree, scaled by 1024

cordicAtan2()

int32_t cordicAtan2	(	int32_t	x,
		int32_t	y )

CORDIC approximation of arctan.

Parameters

x	The x component
y	The y component

Returns

The approximation of atan(y/x), in degrees

getAtan2()

int16_t getAtan2	(	int32_t	y,
		int32_t	x )

Calculate the angle of the line from the origin to (x, y), in degrees.

If both x and y are 0, atan2 is undefined and will return 0.

Parameters

y	The Y coordinate of the point to calculate the angle to
x	The X coordinate of the point to calculate the angle to

Returns

int16_t The angle degree, between 0 and 359.

Variable Documentation

sin1024

const int16_t sin1024[91]

Initial value:

= {
    0,   18,  36,   54,   71,   89,   107,  125,  143,  160,  178,  195,  213,  230,  248,  265, 282, 299, 316,
    333, 350, 367,  384,  400,  416,  433,  449,  465,  481,  496,  512,  527,  543,  558,  573, 587, 602, 616,
    630, 644, 658,  672,  685,  698,  711,  724,  737,  749,  761,  773,  784,  796,  807,  818, 828, 839, 849,
    859, 868, 878,  887,  896,  904,  912,  920,  928,  935,  943,  949,  956,  962,  968,  974, 979, 984, 989,
    994, 998, 1002, 1005, 1008, 1011, 1014, 1016, 1018, 1020, 1022, 1023, 1023, 1024, 1024,
}

A table of the first 91 values of (1024 * sin(x)). Only 91 values are necessary because getSin1024() and getCos1024() handle symmetry to calculate the full wave

tan1024

const uint16_t tan1024[91]

Initial value:

= {
    0,    18,   36,   54,   72,   90,    108,   126,   144,   162,   181,   199,  218,  236,  255,  274,
    294,  313,  333,  353,  373,  393,   414,   435,   456,   477,   499,   522,  544,  568,  591,  615,
    640,  665,  691,  717,  744,  772,   800,   829,   859,   890,   922,   955,  989,  1024, 1060, 1098,
    1137, 1178, 1220, 1265, 1311, 1359,  1409,  1462,  1518,  1577,  1639,  1704, 1774, 1847, 1926, 2010,
    2100, 2196, 2300, 2412, 2534, 2668,  2813,  2974,  3152,  3349,  3571,  3822, 4107, 4435, 4818, 5268,
    5807, 6465, 7286, 8340, 9743, 11704, 14644, 19539, 29324, 58665, 65535,
}

A table of the first 91 values of (1024 * tan(x)). Only 91 values are necessary because getTan1024() handles symmetry to calculate the full wave