Open Viper Loader

This project is meant to be an open source replacement of the Viper Loader program that was distributed with the first generation of Viper GC modchip for the Nintendo GameCube.

The first generation of Viper GC chips was programmed through a parallel port interface but was quickly replaced by a USB interface. The original Viper Loader is a Windows-only program that requires a parallel port to be mapped on the I/O address 0x278, 0x378 or 0x3BC, it also shipped with a version of inpout32.dll that does not work on Windows x86-64 (Note that Inpout32 v1.5.0.1 works as a replacement).

This project contains two parts:

• A replacement program for flashing the chip through a good old parallel port (Untested on an actual parallel port but I'm fairly confident it works, let me know if you happen to test it).
• An Arduino sketch that acts as a serial bridge between the loader and the parallel port module of the Viper GC if you don't have a parallel port.

About the Loader:

It's a reverse engineer of the original loader made possible thanks to Ghidra. In its current state the project will only compile on Linux because it makes calls to ioperm and inb/outb to access the parallel port (this can probably be easily changed since some of these function are already wrapped to allow the use of a serial link to the Arduino). The serial link is handled by termios and should build on other POSIX systems.

Build

Simply run make

Run

Usage: ./viper_loader [-h] [-u] [-p port] [-s dev] (-r out_file | -w in_file | -c in_file)
	-r out_file: Dump the content of the modchip into out_file
	-w in_file: Write the content of in_file into the modchip
	-c in_file: Compare the content of in_file with the content of the modchip
Options:
	-u: Disable safe mode
	-p: Use specified IO port address in hexadecimal (default is 0x378)
	-s: Use Arduino serial bridge connected to dev (example /dev/ttyUSB0)
	-h: Displays this usage message

Examples with parallel port

Write a file with parallel port on I/O address 0x278:

./viper_loader -p 0x278 -w ~/banana.vgc

After writing, compare the original file with the content of the chip:

./viper_loader -p 0x278 -c ~/banana.vgc

Examples with serial connection to Arduino

Write a file with the Arduino interface connected to /dev/ttyUSB0

./viper_loader -s /dev/ttyUSB0 -w ~/apple.vgc

After writing, compare the original file with the content of the chip:

./viper_loader -s /dev/ttyUSB0 -c ~/apple.vgc

About the Arduino interface:

It started as a simple replacement for inb and outb but the performance was dreadful (~2 hours to write/read 128 KB) because too much useless blocking IO was being done between the computer and the Arduino. To remediate that, two additional functions have been embedded on the microcontroller in order to keep communication to a minimum, resulting in write/read times of about 18 seconds for 128 KB.

Build and upload

The Makefile relies on arduino-cli and so should you. It is a lot more convenient that the regular Arduino GUI if you know your way across the Linux command line. That being said you can load viper_arduino_bridge.ino in the Arduino GUI to compile and upload it.

make arduino_upload

This will build the sketch for an Arduino Nano with the old bootloader and upload it on default serial port /dev/ttyUSB0 and uses a Baud Rate of 1000000 to communicate. Adapt these values to your environement by editing the following variables in the Makefile

ARDUINO_FQBN = arduino:avr:nano:cpu=atmega328old
ARDUINO_IFACE = /dev/ttyUSB0
BAUD_RATE = 1000000

Alternatively you can invoke make with these parameters to override them:

make arduino_upload ARDUINO_FQBN="arduino:avr:uno" ARDUINO_IFACE="/dev/ttyUSB1" BAUD_RATE="500000"

Obviously if you change the Baud Rate you will need to (re)build viper_loader with the same value.

Wiring

The Viper GC parallel module only uses uses a few of the parallel interface pins so you will only require 9 wires to get it working. The Arduino uses 5V logic levels just like a parallel port and resistors are present on the parallel module so you can run direct wires.

DB-25 (Name)	Arduino Nano
2 (D0)	Digital D2
3 (D1)	Digital D3
4 (D2)	Digital D4
5 (D3)	Digital D5
6 (D4)	Digital D6
7 (D5)	Digital D7
13 (SELECT)	Digital D8
15 (ERROR)	Digital D9
25 (GND)	GND

Unlicense

This is free and unencumbered software released into the public domain.

Anyone is free to copy, modify, publish, use, compile, sell, or distribute this software, either in source code form or as a compiled binary, for any purpose, commercial or non-commercial, and by any means.

In jurisdictions that recognize copyright laws, the author or authors of this software dedicate any and all copyright interest in the software to the public domain. We make this dedication for the benefit of the public at large and to the detriment of our heirs and successors. We intend this dedication to be an overt act of relinquishment in perpetuity of all present and future rights to this software under copyright law.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

For more information, please refer to https://unlicense.org