Megadrive Reset Mod

In-Game Reset mod with region switching feature (language and 50/60 Hz framerate) for SEGA Megadrive/Genesis. Based on Arduino compatible boards. Arduino Pro Mini (ATmega328 or ATmega168) is recommended.

Features

• In-game reset using player one controller:
  • START + A + B + C - Soft Reset
  • START + A + B + C + DOWN - Hard Reset (if enabled, read below)
• Region switching using player one controller:
  • START + B + LEFT - Switch to North American region (Blue)
  • START + B + RIGHT - Switch to European region (Red)
  • START + B + UP - Switch to Japanese region (Purple)
  • START + B + DOWN - Switch to Asian region (Green)
• Only language switching mode (if configured, read below):
  • START + B + LEFT - Switch to English (Red)
  • START + B + RIGHT - Switch to Japanese (Green)
• Only framerate switching mode (if configured, read below):
  • START + B + UP - Switch to 60 Hz (Red)
  • START + B + DOWN - Switch to 50 Hz (Green)
• Region switching by keep pushed RESET button to cycle through regions/modes.
• Last used mode is saving and reused on next power on.
• Supported only RGB led.
• Configurable mode switching - only language switching or only 50/60 Hz framerate switching (read below).

Building

Source code can be used by Arduino IDE or can be compiled using avr-toolchain.

Configuration

Program behavior can be configured by defines that can be found in main.c file:

• ONLY_LANGUAGE_SWITCH - Use only language switching
• ONLY_FREQUENCY_SWITCH - Use only framerate switching
• HARD_RESET_ENABLED - Enable Hard Reset on separate pin on Arduino board
• RGB_LED_ENABLED - Using RGB LED
• RGB_LED_ANODE - Using RGB LED with common ANODE, else with common CATHODE
• POLL_BY_MCU_ENABLED - If no pad polling by Megadrive, MCU will poll pad itself (useful if console is halted)
• ATMEGA_CLONE_USED - Using cloned ATmega MCU (eg LGT328P), it's adding few NOP's to add some delay before reading buttons state in interrupt handler

Note: It's possible need to add few NOP's manually for MCU you using.

Installation

Here is a simplest connection pinout Arduino board to Megadrive board (without illustration):

Arduino		Megadrive board
5V	<-	Pad Port Pin 5 or another +5V source point (VCC)
GND	<-	GND
(PD2) D2	<-	Pad Port Pin 7 (TH, SEL)
(PD3) D3	<-	Reset Button Pin/Leg (Reset Input)
(PD4) D4	<-	Pad Port Pin 6 (TL, DAT4)
(PD5) D5	<-	Pad Port Pin 9 (TR, DAT5)
(PD6) D6	->	Reset Button Point on Board (Soft Reset Output)
(PD7) D7	->	Cart Slot Pin B2 (#MRES, Hard Reset) optional
(PB0) D8	<-	Pad Port Pin 1 (DAT0)
(PB1) D9	<-	Pad Port Pin 2 (DAT1)
(PB2) D10	<-	Pad Port Pin 3 (DAT2)
(PB3) D11	<-	Pad Port Pin 4 (DAT3)
(PB4) D12	--	X
(PC0) A0	->	LED Blue optional
(PC1) A1	->	LED Green optional
(PC2) A2	->	LED Red optional
(PC3) A3	->	JP1/2 (Language) and to MultiBIOS Pin 39
(PC4) A4	->	JP3/4 (Video Mode) and to MultiBIOS Pin 38
(PC5) A5	--	X

Pictures will be added soon.