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README.md

PadSwitcher64

alt text Interface to allow Super Nintendo (SNES) control pads to be plugged into a C64's joystick ports.

The adapter connects to both C64 joystick ports and allows the active port to be changed on the fly with a push of a button. The interface defaults to joystick port two on power on.

Also, the interface allows up to four custom mappings to be programmed using a C64-side application. The custom mappings allow any combination of joystick port two and port one control lines to be mapped to any of the Super Nintendo controller action buttons (A,B,X,Y,L,R). Any of the action buttons can also have an optional rapid-fire function applied, of which a normal and 'inverted' state is avaliable. 'Inverted' rapid fire is simply that when active the output state of the effected button will be opposite to of a normal rapid fire button when pushed. For example, mapping a button to joystick left with rapid fire and another button to joystick right with inverted rapid fire will simulate a rapid left/right joystick waggle when both buttons are pushed.

This code was originally developed for the Atmel ATMega8 mcu and was then later ported over to the ATMega88. This was mainly due to the availiablilty of the Mega8 and that the Mega88 has more power saving features.

This source code was written using AVR-GCC and AVR Libc.

A pre-compiled HEX file for the AVR and the C64-side software for setting the custom mappings can be found in the releases section.

TODO :

  • Re-jig command mode for potential compatibility with non-C64 Atari joystick compatible machines.
  • Maybe figure out how to support two pads while still retaining some semblence of mapping support.

Pad Mapping: (default)

SNES C64
DPAD UP UP
DPAD DOWN DOWN
DPAD LEFT LEFT
DPAD RIGHT RIGHT
Y FIRE
X TURBO FIRE
B UP
A 'Special'(*1)
R KEYBOARD MATRIX LINE(PORT 2 MODE ONLY)(*2)

(*1) - UP + FIRE or DOWN + FIRE, swapped with SELECT + L.

(*2) - Defaults to PB4 which most software will interpret as the SPACEBAR.

Fixed Controls:

Button/Combo Function
SELECT + UP Toggle disable of D-PAD UP
START Swap Joystick control port
SELECT + L Toggle 'Special' function
SELECT + R Change keyboard matrix line (*3)
SELECT + DOWN Toggle TURBO FIRE rate
SELECT + (A,B,X,Y) Select mapping
SELECT + START Default Mapping
SELECT + START Enter Command Mode (*4)
SELECT + START + L + R
(In normal or mapped mode) Enter type 1 direct mode
(In any other mode) Force normal mode

(*3) - Joystick port 1, which corresponds to CIA 1 PB0 to PB4, PB4 which are normally used as the keyboard input lines during keyboard scanning. By default at startup this is set to PB4, which most software will interpret as the SPACEBAR.

CIA1 PortB CIA1 PA7 PA6 PA5 PA4 PA3 PA2 PA1 PA0
PB4 SPACE R-SHIFT . M B C Z F1/F2
PB3 2 CLR/HOME - 0 8 6 4 F7/F8
PB2 CTRL ; L J G D A CRSR
PB1 <- * P I Y R W RETURN
PB0 1 £ + 9 7 5 3 INST/DEL

(*4) - Only functional when prompted, only functional in default mapping mode.

MAPPING

Four mappings, each with all 6 action buttons available. Each button has a 2 byte pattern corresponding to the following:

Byte/Bit Function
Byte 1 - Bit 0 to 3 PB0 to PB3 (JOY 1 Directions & KB matrix)
Byte 1 - Bit 4 to 7 PA0 to PA3 (Joy 2 directions)
Byte 2 - Bit 0 PB4 (Joy 1 Fire & KB matrix)
Byte 2 - bit 1 PA4 (Joy 2 Fire)
Byte 2 - bit 2 Pad Button has turbofire action
Byte 2 - Bit 3 Pad Button has turbofire action (inverted)

Bits 4 - 7 of byte 2 are not accessible through the command interface at this time.

Direct mode - Type 1

Direct mode allows all the SNES control pad buttons to be read by the C64. Type 1 uses both joystick port to report all buttons. There is technically a direct mode type 2, and that is by using the command interface. Type one is much faster as it just involves reading the joystick ports normally.

SNES Pad C64 CIA Bit pattern C64 Joystick
Up DC00 11110 Port 2 up
Down DC00 11101 Port 2 down
Left DC00 11011 Port 2 left
Right DC00 10111 Port 2 right
Y DC00 01111 Port 2 fire
Start DC00 00000 Port 2 all
B DC01 11110 Port 1 up
X DC01 11101 Port 1 down
L DC01 11011 Port 1 left
R DC01 10111 Port 1 right
A DC01 01111 Port 1 fire
Select DC01 00000 Port 1 all

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Interface to allow Super Nintendo (SNES) control pads to be plugged into a C64's joystick ports.

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