GBcamera ImageSaver

I have just found an old code I wrote, some time ago, to get Game boy camera images from the cartridge and save them in a computer. Probably nobody cares anymore about Game Boy and Game Boy Camera, I can imagine. But I was born in the 80’s, and for me that’s still funny.

Ok! I know GB Camera has only 23kpx monochrome sensor, but in 1998 Casio just launched Casio QV-10 with 250kpx sensor and one year later Nikon released Nikon D1 (2.8Mpx). Unfortunately at that time I was too young for a 6k$ camera.

So GameBoy Camera was a pretty awesome toy in the late 90’s. With GB camera you could take pics and check them without waiting for any chemical process. There is a menu for editing the photos with endless options, and another one to make funny animations. You can even rotate the lens to make selfies!

I still keep two GameBboy Camera cartridgse but unfortunately I lost all the pictures I took when I was a kid. I don’t understand why Nintendo never thought on selling a software to save the images into a computer. The best you could do was to buy a  Nintendo Printer, but It was really expensive and It never got popular in my country. When internet arrived, I bought a MadCatz cable to transfer images to the PC. But I have to say that the software was very awful, and the interface need a LPT port therefore nowadays It’s useless. So I have always being looking for an alternative.

On google you can find some tutorials from people that uses different hardware and software, but most of the times it is not easy to find the hardware and the code is not shared. So I started playing with my fancy new arduino board and that’s the result.

It was the first (and last time) I used arduino. Previously I only used PIC microcontrollers (16f and 18f). I have to say that arduino compiler is not as friendly as I thought. Maybe I should read a little more about it. And for sure the arduino IDE is very poor (but enough), but possibly it would get better on eclipse. Arduino is very limited but the key point is the price, 13 $ for an Arduino Uno shipping included. It’s a very impressive price. It deserves a chance. (If you’re not familiar with it, Arduino consists of an open-source hardware board designed around an 8-bit Atmel AVR microcontroller and IDE toolset).

The propose of this project was to copy same idea as MadCadz cable: to use the communication port between  Game Boy and Game Boy Printer to get the image data without losing any bit. The first I discover on GameBoy Dev’rs was the pin out. Then I just took the oscilloscope and started taking notes of everything. Here you can find a few:

At first sight, it doesn’t look so difficult: It seems like a regular SPI bus: f(SCK) = 8.199 kHz, Vmax = 5.00 V.

On the second screen image you can see the information needed for the bus setup,  Arduino SPI – slave mode: CPOL = 1 and CPHA = 1, that correspond to SPI mode 3.
Below I write the basic code to run SPI as slave for GB camera and put the data to Serial bus.  It was the most difficult part of the project, I think that when you start coding with arduino is not easy to understand how to use all ATMEL periferics. To write a byte to SPI you just have to write it in SPDR register. Maybe it is useful for your own project:

</pre>
<blockquote>
#include "pins_arduino.h"

// Buffer to put incoming data (from GB):
byte buf [100];
volatile byte bufPos;

void setup (void)
{
// Serial Debugging
Serial.begin (115200);

// SPI CONFIGURATION
// ==================

// Have to send on master in, *slave out*
pinMode(MISO, OUTPUT);
pinMode(SS, INPUT);

// Turn on SPI in slave mode
SPCR &= ~_BV(MSTR);

// Set: MSb is writen first
SPCR &= ~_BV(DORD);

// Set SPI Mode 3
SPCR |= _BV(CPOL);
SPCR |= _BV(CPHA);

// Turn on interrupts
SPCR |= _BV(SPIE);

// Enable SPI
SPCR |= _BV(SPE);

// END SPI CONFIGURATION
// ==================

// Initiate buffers
SPDR = 0;
bufPos = 0;

Serial.println("Setup done.");
} // End of setup
// SPI interrupt routine
ISR (SPI_STC_vect){

if (bufPos < 100){
buf [bufPos++] = SPDR;
} // end of room available
SPDR = 0;
} // End of interrupt service routine (ISR) SPI_STC_vect

void loop (void){
while(1){
if (bufPos > 0) {
bufPos = bufPos - 1;
Serial.println(buf [bufPos],DEC);
}
} // End of while (1)
} // End of main loop

As you can finally see the code is quite simple. You need to read Atmel datasheet to fully understand it. I decided to use Atmel register directly to write and read to SPI bus without using arduino SPI.h library because I could not understand how to use it.

These are the registers and the values I used:

You can find more information about how to connect the pins here.

With that code the only blocking point is to understand completely the communication between the Game Boy and the Printer just to emulate Printer answer and extract the image information. I use a cheap logic analyzer from dangerous prototypes to start working on the communication: Open Bench Logic Sniffer. It can work up to 100MHz waveforms on 16 channels! Here is the configuration and the result I get:

It confirms the information I got from the oscilloscope, but at the end it was not so easy to use. So finally I used Bus Pirate also from Dangerous Prototypes. To run Bus Pirate for this propose type the following commands: [m, 5, 1, 2, 1, 1, 2, (1), 3].

With this document and google help this is how I understand the communication between GameBoy and the Printer:

This table shows that GB always starts the communication with 0x88h and 0x33h bytes. After GB sends the command code [0x01h: to intialize, 0x02h: to print, 0x04h: for sending data and 0x0Fh: for Inquiry] and so on. So, at the end,  all that Arduino has to do is to send acknowledgement code (0x81h or 0x88h) and status code (0x00h) after checksum bytes.

The data format is as follows:

Each image corresponds to a page. Each page consists on 9 brands. And Each brand consists on 40 tiles. GB sends a data command for each brand (640bytes).

The brand structure is not so simple, but it may help:

Putting all the bits in the correct order the result should be something like that:

 

And that’s the result:

      

You can find all code here: https://github.com/gism/GBcamera-ImageSaver. Probably you would like to change conf.py file.

I used an Arduino nano board, but I think all the boards have the same pinout for connecting Arduino board with the game boy:

 

And that’s the result, an USB interface for Game boy 😀

 

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