sin16_C()

LIB8STATIC int16_t sin16_C

(

uint16_t

theta

)

Fast 16-bit approximation of sin(x).

This approximation never varies more than 0.69% from the floating point value you'd get by doing

float s = sin(x) * 32767.0;

Parameters

theta

input angle from 0-65535

Returns

sin of theta, value between -32767 to 32767.

Definition at line 113 of file trig8.h.

                                           {
    static const uint16_t base[] = {0,     6393,  12539, 18204,
                                    23170, 27245, 30273, 32137};
    static const uint8_t slope[] = {49, 48, 44, 38, 31, 23, 14, 4};
 
    uint16_t offset = (theta & 0x3FFF) >> 3; // 0..2047
    if (theta & 0x4000)
        offset = 2047 - offset;
 
    uint8_t section = offset / 256; // 0..7
    uint16_t b = base[section];
    uint8_t m = slope[section];
 
    uint8_t secoffset8 = (uint8_t)(offset) / 2;
 
    uint16_t mx = m * secoffset8;
    int16_t y = mx + b;
 
    if (theta & 0x8000)
        y = -y;
 
    return y;
}

References LIB8STATIC, offset(), and y.

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