Awesome

A simple PC to Game Boy Printer interface with an Arduino

The most cheap and basic setup you can imagine to print something from a PC to a Game Boy Printer ! The Arduino code is the same used in the GBCamera-Android-Manager. The code originates from an SD based version which is more stable and time accurate but requires an SD shield. The project here requires nothing but an Arduino Uno and a PC.

Alternatively, you can directly use the Game Boy printer emulator, it is compatible ! Just connect the serial cable with printer ON, boot the Arduino and it will recognize the printer with exactly the same hardware setting ! For the story, it contains the small Arduino core proposed here wrapped with a printer detection routine. The code first pings for a printer before switching to its normal emulator mode.

Here GNU Octave is used to encode images into Game Boy Tile Format, make legit printer packets with correct checksums and send them to the serial port in correct order. The Arduino acts as a luxury level shifter. It turns the asynchronous serial data sent to the Arduino into an SPI protocol compatible with the printer, in particular regarding timings and synchronous communication.

Parts needed

• An Arduino Uno;
• The cheapest Game Boy serial cable you can find as you will cut it. Important note: SIN and SOUT are crossed internally so never trust what wires you get. Use a multimeter to identify wires. Cross SIN and SOUT if the device does not work at the end;
• If you want something working first try, you can use a serial port breakout board instead of cutting/soldering a cable.
• If you want something blinking, you can wire an aditionnal fancy LED to D13 with a 200-1000 Ohm resistor in series.

Pinout

The pinout uses only 4 wires, so it's very easy to make ! It must even work without SOUT connected !

Dedicated PCB

If you want something very neat, you can follow the instructions given here to build a dedicated PCB. This PCB is also compatible with many other projects.

How to use it

Well, this is as simple as it sounds:

• Install the Arduino IDE and GNU Octave;
• Clone the repo locally;
• Flash the Arduino code to your Arduino Uno. Change the pinout if necessary;
• Drop some images, any size, any number of colors, png format, in the image folder. 1x screenshots, 4 colors, made from emulators and images from Game Boy Camera fit perfectly the native printer resolution but are not mandatory. Other formats will be reduced to 160x(16xX), 2 bits per pixel images, Bayer dithering (like the Game Boy Camera);
• Connect the Game Boy Printer to the Arduino and the Arduino to the PC. The Arduino is ready as soon as the LED wired to D13 turns ON;
• Open the Octave code, select the COM port corresponding to your Arduino board and run the code from the GNU Octave Launcher. You must see some flashes of the LED if it's working;
• Enjoy your washed-out pictures !
• The Arduino onboard LEDs blink and it does not print ? Inverse physically SIN and SOUT, then retry !

The lazy protocol used here

This code prints one packet after the other and uses a fixed timer intervall inbetween packets to let time to the printer to print (while sending inquiry packets to occupy the printer). This is the most basic printer protocol implementation possible (aka "lazy open loop implementation"). It was validated on both Seiko and Hosiden printers.

Due to some timing inconsistencies, I sometimes loose randomly the synchronization if I send the packets 9 by 9 (maximum possible), so I have to restart protocol from scratch (INIT command) at each data packet. It has hopefully no adverse effect on printing quality and very minor effect on printing velocity.

Example of fancy use: printing emulator screenshots

Have you run out of paper ?

The repo also comes with a fake printer that allows you to generate completely fake thermal prints having exactly the aspect of what a Game Boy Printer could produce. No batteries or thermal paper required !

Funfact

The printer code is compatible with printer emulators like the BitBoy, The Arduino Game Boy Printer Emulator or the NeoGB Printer. This has strictly no interest apart from debugging the project without using batteries and paper.

Acknowledgements

• Andreas Hahn for the dithering pattern generator which I took inspiration from.
• Mraulio for help and debugging