q15_t arm_sin_q15(q15_t x)
{
  q15_t sinVal;                                  /* Temporary variables for input, output */
  int32_t index;                                 /* Index variables */
  q15_t a, b;                                    /* Four nearest output values */
  q15_t fract;                                   /* Temporary values for fractional values */

  /* Calculate the nearest index */
  index = (uint32_t)x >> FAST_MATH_Q15_SHIFT;

  /* Calculation of fractional value */
  fract = (x - (index << FAST_MATH_Q15_SHIFT)) << 9;

  /* Read two nearest values of input value from the sin table */
  a = sinTable_q15[index];
  b = sinTable_q15[index+1];

  /* Linear interpolation process */
  sinVal = (q31_t)(0x8000-fract)*a >> 16;
  sinVal = (q15_t)((((q31_t)sinVal << 16) + ((q31_t)fract*b)) >> 16);

  return sinVal << 1;
}