Subversion Repositories openmsp430

// ************************************************************

// global variables

//

// sine table 0 - 64 binary degrees

// rocket size of 128 calculated into table

/* Description:

Contains byte values for scaled rocket size values for the first quadrent

of angles.

*/

const char sintbl[] = {

  0, 3, 6, 9, 12, 15, 18, 21,

  24, 28, 31, 34, 37, 40, 43, 46,

  48, 51, 54, 57, 60, 63, 65, 68,

  71, 73, 76, 78, 81, 83, 85, 88,

  90, 92, 94, 96, 98, 100, 102, 104,

  106, 108, 109, 111, 112, 114, 115, 117,

  118, 119, 120, 121, 122, 123, 124, 124,

  125, 126, 126, 127, 127, 127, 127, 127,

  128

  };

// ************************************************************

//

//    blitzkrieg sine routine

//

//    enter angle to be converted

//

/* Description:

Fast lookup table sine routine.  The sine routine uses 256 units for a

complete circle.

The first  quadrent is 0x00 - 0x3f ->   0 -  89 degrees.

The second quadrent is 0x40 - 0x7f ->  90 - 179 degrees.

The third  quadrent is 0x80 - 0xbf -> 180 - 269 degrees.

The fourth quadrent is 0xc0 - 0xff -> 270 - 359 degrees.

This fuction is call as a cosine by adding 64 to the angle to return the x

vector part of the rocket size.  This fuction is call as a sine to return the y

vector part of the rocket size.

*/

int bzsin(char angle)

{

  int sine;

  if(angle & 0x40) angle = angle ^ 0x3F;  // invert angle in second quad

  sine = sintbl[angle & 0x3F];            // convert char to int

  return (angle & 0x80) ? -sine : sine ;  // change sign for 180 - 360 degrees

}