src/libjoystick/joystick.c

   1 /* joystick emulation
   2  *
   3  * (C) 2018 by Andreas Eversberg <jolly@eversberg.eu>
   4  * All Rights Reserved
   5  *
   6  * This program is free software: you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation, either version 3 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include <stdio.h>
  21 #include <stdint.h>
  22 #include <string.h>
  23 #include "joystick.h"
  24
  25 static int joystick_left = 0;
  26 static int joystick_right = 0;
  27 static int joystick_up = 0;
  28 static int joystick_down = 0;
  29 static int joystick_fire = 0;
  30 static int joystick_left_reset = 0;
  31 static int joystick_right_reset = 0;
  32 static int joystick_up_reset = 0;
  33 static int joystick_down_reset = 0;
  34 static int joystick_fire_reset = 0;
  35
  36 #define CIAAPRA         0xbfe000
  37 #define JOYDAT1         0xdff00c
  38
  39 uint16_t emulate_joystick_read(uint32_t address)
  40 {
  41         if (address == CIAAPRA) {
  42                 if (joystick_fire)
  43                         return 0xff7f;
  44                 return 0xffff;
  45         }
  46
  47         if (address == JOYDAT1) {
  48                 uint16_t joydat = 0x0000;
  49                 if (joystick_right) {
  50                         joydat |= 0x0002;
  51                         /* make bit 0 and 1 equal */
  52                         if (!joystick_down)
  53                                 joydat |= 0x0001;
  54                 } else {
  55                         /* make bit 0 and 1 odd */
  56                         if (joystick_down)
  57                                 joydat |= 0x0001;
  58                 }
  59                 if (joystick_left) {
  60                         joydat |= 0x0200;
  61                         /* make bit 8 and 9 equal */
  62                         if (!joystick_up)
  63                                 joydat |= 0x0100;
  64                 } else {
  65                         /* make bit 8 and 9 odd */
  66                         if (joystick_up)
  67                                 joydat |= 0x0100;
  68                 }
  69                 return joydat;
  70         }
  71
  72         return 0xffff;
  73 }
  74
  75 /* use -1 to keep state unchanged */
  76 /* NOTE: a pressed and then released button/stick will sustain until reset_joystick() is called after rendering was done.
  77  * this ensures that a short press (during rendering one frame) will not get lost.
  78  */
  79 void set_joystick(int left, int right, int up, int down, int fire)
  80 {
  81         if (left == 1)
  82                 joystick_left = 1;
  83         if (left >= 0)
  84                 joystick_left_reset = left;
  85         if (right == 1)
  86                 joystick_right = 1;
  87         if (right >= 0)
  88                 joystick_right_reset = right;
  89         if (up == 1)
  90                 joystick_up = 1;
  91         if (up >= 0)
  92                 joystick_up_reset = up;
  93         if (down == 1)
  94                 joystick_down = 1;
  95         if (down >= 0)
  96                 joystick_down_reset = down;
  97         if (fire == 1)
  98                 joystick_fire = 1;
  99         if (fire >= 0)
 100                 joystick_fire_reset = fire;
 101 }
 102
 103 void reset_joystick(void)
 104 {
 105         joystick_left = joystick_left_reset;
 106         joystick_right = joystick_right_reset;
 107         joystick_up = joystick_up_reset;
 108         joystick_down = joystick_down_reset;
 109         joystick_fire = joystick_fire_reset;
 110 }
 111