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[/] [openmsp430/] [trunk/] [fpga/] [actel_m1a3pl_dev_kit/] [software/] [spacewar/] [bzsin.c] - Rev 158
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// ************************************************************ // 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 }
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