sin8_C()

LIB8STATIC uint8_t sin8_C

(

uint8_t

theta

)

Fast 8-bit approximation of sin(x).

This approximation never varies more than 2% from the floating point value you'd get by doing

float s = (sin(x) * 128.0) + 128;

Parameters

theta

input angle from 0-255

Returns

sin of theta, value between 0 and 255

Definition at line 240 of file trig8.h.

                                         {
    uint8_t offset = theta;
    if (theta & 0x40) {
        offset = (uint8_t)255 - offset;
    }
    offset &= 0x3F; // 0..63
 
    uint8_t secoffset = offset & 0x0F; // 0..15
    if (theta & 0x40)
        ++secoffset;
 
    uint8_t section = offset >> 4; // 0..3
    uint8_t s2 = section * 2;
    const uint8_t *p = b_m16_interleave;
    p += s2;
    uint8_t b = *p;
    ++p;
    uint8_t m16 = *p;
 
    uint8_t mx = (m16 * secoffset) >> 4;
 
    int8_t y = mx + b;
    if (theta & 0x80)
        y = -y;
 
    y += 128;
 
    return y;
}

References b_m16_interleave, LIB8STATIC, offset(), and y.

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