MultiJoy CC65 library

For Atari 8-bit Computers

By Bill Kendrick
January 2019

About

This is a simple library for use with the cc65 C compiler, targetting Atari 8-bit computers, and using a MultiJoy adapter to allow up to 8 joysticks to be connected to an unmodified Atari computer.

References

• MULTIJOY - Radek Štěrba / RASTER & Atariklub Prostějov (Czech)
• MULTIJOY8
• How to query the MultiJoy Interface

Features

This is a work in progress

• Set-up function
  Initializes the joystick ports for correct I/O necessary for use with MultiJoy
• Direct joystick read
  Simple function to query a particular joystick's state
• Constant joystick querying mode
  A chained pair of Display List Interrupt routines are available to constantly query each joystick, one by one, and store their state in memory, for reading as-needed.
• Simple demo programs
  • mj_test - Read all 8 joystick directions and firebuttons and show symbols on the screen to reflect their state
  • mj_draw - Each of 8 joysticks controls a number which can be moved around the screen independently. Hold fire to leave a trail; release to erase
  • mj_robo - A simple four-player game using two joysticks per player, one controlling movement, and one controlling the firing of bullets (up to 4 at a time, per player), à la Robotron: 2084. Each player has 8 energy units (shown at the bottom), and will disappear once it's been exhausted, by being fired upon. Inverse (ding!) alphabetic characters are placed the screen randomly, as obstacles. Firing them decreases the letter, until they reach "A", after which point a shot completely destroys them.

  To Do

  As of 2019-01-27:

  • Allow DLI to store of joystick values in an arbitary location (currently uses page 6 ($600 thru $60F))
  • Allow DLIs to be chained off of a user DLI routine (e.g., for typical visual effects, etc.)
  • Proper documentation
  • Better directory layout
  • Add sound, score, and a game over event to the mj_robo game.

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  Usage

  Include the header

  #include <atari.h>
  #include "atari_multijoy.h"
  

  Initialize the port

  multijoy_init(true);
  

  Set up screen and display list

  For example, here's a "GRAPHICS 0" screen set up to invoke the DLIs every modeline (so query, and read, consecutive sticks 12 times per frame).

  unsigned char i;
  unsigned char * DLIST;
  unsigned char old_sdmctl;
  
  DLIST = (unsigned char *) SDLST;
  
  _graphics(0);
  
  old_sdmctl = multijoy_dli_init_1();
  DLIST[3] = DL_DLI(DL_LMS(DL_GRAPHICS0));
  for (i = 6; i < 29; i++) {
    DLIST[i] = DL_DLI(DL_GRAPHICS0);
  }
  multijoy_dli_init_2(old_sdmctl);
  

  Read whatever stick & firebutton state you want

  unsigned char * PAGE6 = (char *) (0x600);
  unsigned char s;
  bool f;
  
  s = PAGE6[2]; /* Joystick #3 */
  f = PAGE6[2 + 8]; /* Firebutton #3 */
  

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  Download

  • multijoy_cc65_20190127.tar.gz
    Source code to the library and sample programs, and Makefile
  • multijoy_cc65_20190127.atr
    Sample programs, compiled, and stores on a single Atari floppy disk image (along with MyDOS)

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  bill@newbreedsoftware.com | New Breed Software