Embedded Software and Motor Control Libraries for PXR40xx

Function GFLIB_AtanYX_FLT
In the second step, the vector ordinate is divided by the vector abscissa (y/x) to obtain the
tangent value of the angle offset. The angle offset is computed by applying the ordinary
arctangent function.
The sum of the integral multiple of half-quarters and the angle offset within a single halfquarter
form the angle to be computed. The function will return 0 if both input arguments
are 0.
In comparison to the GFLIB_Atan_F16 function, the GFLIB_AtanYX_F16 function
correctly places the calculated angle within the whole fractional range of [-1, 1), which
corresponds to the real angle range of [- π, π).
Note
The function calls the GFLIB_Atan_F16 function. The
computed value is within the range of [-1, 1).
4.35.5 Re-entrancy
The function is re-entrant.
4.35.6 Code Example
#include "gflib.h"
tFrac16 f16InY;
tFrac16 f16InX;
tFrac16 f16Ang;
void main(void)
{
// Angle 45 deg = PI/4 rad
f16InY = FRAC16 (0.5);
f16InX = FRAC16 (0.5);
}
// output should be close to 0x2000
f16Ang = GFLIB_AtanYX_F16 (f16InY, f16InX);
// output should be close to 0x2000
f16Ang = GFLIB_AtanYX (f16InY, f16InX, Define F16);
// ##############################################################
// Available only if 16-bit fractional implementation selected
// as default
// ##############################################################
// output should be close to 0x2000
f16Ang = GFLIB_AtanYX (f16InY, f16InX);
Embedded Software and Motor Control Libraries for PXR40xx, Rev. 1.0
250 Freescale Semiconductor, Inc.