Hello all,

I have a fixed-point function (16.16) that calculates SIN and COS from a lookup table. However, since the LUT is in the range 0-360 (degrees), how do I convert an arbitrary angle (e.g. 535.2) to the range 0-360.

Usually a simple MOD would do it:

However in fixed point, you can't just do that, so a way to do it is:Code:angle2 = angle % 360;

But surely there is a faster way?Code:angle2 = angle - fixmul(fixfloor(fixdiv( angle,360 )),360); // same as (floating point): angle2 = angle - ( floor( angle/360 ) * 360 );

EDIT: Here is the whole function which looks up sin in a LUT which has one value for each degree, then does linear interpolation for partial degrees (e.g. 120.75 degrees).

Code:fixed fixsin(fixed x){ int a, b; fixed c, d, val; // First ensure value is 0-360 (not including 360) x = x - itofix(fixfloor(fixdiv( x,FIX360 )) * 360); if (x<0){ x=-x; } // Get the index directly before and after point a = fixfloor(x); b = a+1; if (b>359){ b=0; } // Get the sin values directly before and after point c = _sin_lut[ a ]; d = _sin_lut[ b ]; // Do linear interpolation to get actual value return c + fixmul((d-c),(x-itofix( a ))); }