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
  31 #define CIAAPRA         0xbfe000
  32 #define JOYDAT1         0xdff00c
  33
  34 uint16_t emulate_joystick_read(uint32_t address)
  35 {
  36         if (address == CIAAPRA) {
  37                 if (joystick_fire)
  38                         return 0xff7f;
  39                 return 0xffff;
  40         }
  41
  42         if (address == JOYDAT1) {
  43                 uint16_t joydat = 0x0000;
  44                 if (joystick_right) {
  45                         joydat |= 0x0002;
  46                         /* make bit 0 and 1 equal */
  47                         if (!joystick_down)
  48                                 joydat |= 0x0001;
  49                 } else {
  50                         /* make bit 0 and 1 odd */
  51                         if (joystick_down)
  52                                 joydat |= 0x0001;
  53                 }
  54                 if (joystick_left) {
  55                         joydat |= 0x0200;
  56                         /* make bit 8 and 9 equal */
  57                         if (!joystick_up)
  58                                 joydat |= 0x0100;
  59                 } else {
  60                         /* make bit 8 and 9 odd */
  61                         if (joystick_up)
  62                                 joydat |= 0x0100;
  63                 }
  64                 return joydat;
  65         }
  66
  67         return 0xffff;
  68 }
  69
  70 /* use -1 to keep state unchanged */
  71 void set_joystick(int left, int right, int up, int down, int fire)
  72 {
  73         if (left >= 0)
  74                 joystick_left = left;
  75         if (right >= 0)
  76                 joystick_right = right;
  77         if (up >= 0)
  78                 joystick_up = up;
  79         if (down >= 0)
  80                 joystick_down = down;
  81         if (fire >= 0)
  82                 joystick_fire = fire;
  83 }
  84
  85