topic Re: How to calculate arctan(x)? in S12 / MagniV Microcontrollers

How to calculate arctan(x)?

aaronlee — Mon, 25 Jan 2021 08:14:50 GMT

How to calculate arctan(x), sin(x), cos(x) in S12ZVCA ?

Best Regards,

Aaron

Re: How to calculate arctan(x)?

lama — Mon, 25 Jan 2021 10:32:07 GMT

Hi,

you can use standard CodeWarrior library functions. however they are relatively (depends on application) slow:

#include <math.h>

double atan(double x);

float atanf(float x);

long double atanl(long double x);

Another possibility is to use math and control library which uses fractional arithmetics and polynomial substitution of the functions:

Search for mc9s12zvm_ammclib at nxp.com to get more info or

https://www.nxp.com/design/automotive-software-and-tools/nxp-automotive-math-and-motor-control-library-ammclib-set:AMMCLIB?tab=Design_Tools_Tab

to download. (you must press "more" to find library in collapsed list)

Best regards,

Ladislav

The last possibility is to use own searching table...depends on required precisiion.

Re: How to calculate arctan(x)?

aaronlee — Tue, 26 Jan 2021 04:39:26 GMT

Hi Ladislav,

Very useful. Thank you.

Best Regards,

Aaron

Re: How to calculate arctan(x)?

aaronlee — Sat, 21 Aug 2021 23:01:32 GMT

Share my code "Clockwise Rotation"

from (A, B) to (X,Y)

#include "math.h" double atan(double); float atanf(float); int16_t iA, iB, iX, iY; float fAngle, fDistance, fRotate; fAngle = atan2f (iB, iA); fDistance = sqrt(pow(iA,2) + pow(iB,2)); iX = fDistance * cos(fAngle - fRotate); iY = fDistance * sin(fAngle - fRotate);

Best Regards,

Aaron

Reference:

Determining clockwise vs counter clockwise rotations

Determining angle of rotation