Embedded Software and Motor Control Libraries for PXR40xx

4.36 Function GFLIB_AtanYX_FLT
The function calculates the angle between the positive x-axis and the direction of a vector
given by the (x, y) coordinates.
4.36.1 Declaration
tFloat GFLIB_AtanYX_FLT(tFloat fltInY, tFloat fltInX);
4.36.2 Arguments
Table 4-46. GFLIB_AtanYX_FLT arguments
Type Name Direction Description
tFloat fltInY input The ordinate of the input vector (y coordinate).
tFloat fltInX input The abscissa of the input vector (x coordinate).
4.36.3 Return
The function returns the angle between the positive x-axis of a plane and the direction of
the vector given by the x and y coordinates provided as parameters.
4.36.4 Description
Chapter 4 API References
The function returns the angle between the positive x-axis of a plane and the direction of
the vector given by the x and y coordinates provided as parameters. The first parameter,
fltInY, is the ordinate (the y coordinate) and the second one, fltInX, is the abscissa (the x
coordinate).
Both the input parameters are assumed to be in the single precision floating point range
of (-2 128 , 2 128 ). The computed angle is in the range of [- π, π]. The counter-clockwise
direction is assumed to be positive, and thus a positive angle will be computed if the
provided ordinate (fltInY) is positive. Similarly, a negative angle will be computed for
the negative ordinate. The calculations are performed in a few steps.
In the first step, the angle is positioned within the correct half-quarter of the
circumference of a circle, and if necessary the final angle addition is prepared or the sign
of the input value is corrected.
Embedded Software and Motor Control Libraries for PXR40xx, Rev. 1.0
Freescale Semiconductor, Inc. 251