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olivier.gi |
#include "msp430x20x3.h"
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#include "spacewar.h"
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//************************************************************
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// externals
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//
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extern int bzsin(char);
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//************************************************************
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//
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// update
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//
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// checks rockets buttons and fires its torpedoes
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// updates rockets position
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// updates torpedos position
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//
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/* Description:
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Generates the x, y vectors for the rocket at present angle. Checks the A to D
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passed into function for any keys pressed. The A to D resistors are selected
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to generate values in between the ranges checked. If you push multiple buttons
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strange results will occure. If no keys are pressed the fire flaag clears.
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Rotate counter clockwise increments the angle variable. Rotate clockwise
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decrements the angle variable. If the thrust key is pressed a scaled
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value of xsize and ysize is added into the x and y velocity of the rocket
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creating acceleration. If the fire button is pressed the fire flag is checked.
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If no fire flag then a inactive torpedo is searched for. If a inactive torpedo
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is found the torpedo is given the present position of the rocket plus an x,y
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offset to get it past the nose of the rocket. The torpedo is given the present
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velocity of the rocket plus additional speed based on xsize, ysize.
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The rocket position is updated by adding a scaled velocity into position.
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The position is masked to the DAC maximum. The torpedo positions are updated
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by adding a scaled torpedo velocity into torpedo position. The torpedo
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position is masked to the DAC maximum.
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*/
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void update(rkt_data *rkt, unsigned int new_a2d)
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{
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int i;
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rkt->xsize = bzsin(rkt->ang + 64); // this returns the cosine
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rkt->ysize = bzsin(rkt->ang); // this returns the sine
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if(new_a2d > 0xD000){ // rkt rotate CCW ?
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rkt->ang++; // yes
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}
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else { // no
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if(new_a2d > 0xA000){ // rkt rotate CW ?
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rkt->ang--; // yes
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}
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else { // no
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if(new_a2d > 0x6000) { // is rkt thrusting
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rkt->xvel += ((long) rkt->xsize << 6); // yes
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rkt->yvel += ((long) rkt->ysize << 6);
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}
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else { // no
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if(new_a2d > 0x2000) { // is rkt firing now ?
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if((rkt->flags & fire_bit) == 0) { // did rkt fire last loop ?
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for(i = 0; i < ammo; i++) { // no - look for a torp read to fire
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if(rkt->pt_dx[i] == -1) {
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rkt->flags |= fire_bit; // set firing flag
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rkt->pt_dx[i] = rkt->xdisp + (rkt->xsize << 1); // load up a new torps data
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rkt->pt_dy[i] = rkt->ydisp + (rkt->ysize << 1);
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rkt->pt_vx[i] = (rkt->xvel >> 16) + (rkt->xsize >> 3);
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rkt->pt_vy[i] = (rkt->yvel >> 16) + (rkt->ysize >> 3);
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break;
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}
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}
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}
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} else {
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rkt->flags &= ~fire_bit; // clear fire flag
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}
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}
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}
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}
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rkt->xdisp = (rkt->xdisp + (rkt->xvel >> 16)) & max_dac; // update rkt x position
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rkt->ydisp = (rkt->ydisp + (rkt->yvel >> 16)) & max_dac; // update rkt y position
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for(i = 0; i < ammo; i++) {
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if(rkt->pt_dx[i] != -1) {
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rkt->pt_dx[i] = (rkt->pt_dx[i] + rkt->pt_vx[i]) & max_dac; // move torp x
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rkt->pt_dy[i] = (rkt->pt_dy[i] + rkt->pt_vy[i]) & max_dac; // move torp x
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}
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}
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}
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