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Game Boy WiFi Printer - D1 Mini Shield

Enthusiasts on the Game Boy Camera Club discord server have been working on a Game Boy Printer emulator project based on ESP8266 D1 mini boards. Taking inspiration from other projects like the Gameboy Link Cable Breakout PCB, I created this shield board to add a link connector and pinouts for an oled screen.

Here's a render of the PCB
<img src="images/render.png" alt="3D render of the pcb design" width="50%">

Recommended D1 mini Boards:

LILYGO TTGO D1 mini (recommended) - https://www.aliexpress.com/item/4001144115302.html
Embedded 16340 battery holder, embedded charge curcuit, and embedded power switch.

LOLIN D1 mini Pro - https://www.aliexpress.com/item/32724692514.html
Embedded LiPo battery connector, embedded charge circuit. No embedded power switch.

LOLIN D1 mini - https://www.aliexpress.com/item/32529101036.html
No battery connector, no charge curcit, and no power switch included.

Assembled Printer Example

Here's a photo of an assembled printer using a D1 mini Pro board:
<img src="images/assembled.png" alt="Assembled printer using d1 mini pro" width="50%">

Components

Besides the ESP8266 board, this shield uses the following components:

1× 4.7kΩ resistor (required for link detection)
1x 10kΩ resistor (required for link detection)
1× 128×32 OLED display (optional, recommended)
1× 3.5mm LED (optional)

Placements for the components are clearly marked on the board's silkscreen. The resistors can be either through hole or surface mount type and can be placed either on the top OR bottom of the board.

Compatible Software

This shield breaks out appropriate pins for the Game Boy Link port that is part of the PCB itself. This hardware is suitable for both the Arduino Game Boy Printer Emulator as well as the WiFi Game Boy Printer Emulator

When using this with the WiFi Game Boy Printer Emulator, you can uncomment and adjust the pin on the following lines in your config.h file to detect a connected and powered on Game Boy to auto switch into print mode:

// Sense boot mode lets you use the signal on pin GB_5V_OUT to determine printer/server mode
#define SENSE_BOOT_MODE
#define GB_5V_OUT 16

If you've added the optional OLED display, you can uncomment and adjust the pins on the following lines in your config.h file:

// Uncomment if using an adafruit oled display
#define USE_OLED
// Alternative OLED Pins
#define OLED_SDA 4
#define OLED_SCL 5

Usage

When connecting a Game Boy Link cable to the shield, check the silkscreen for indicators on which side should be placed up. (The flat side of the connector should face down and the rounded side should face up, the same side as the OLED screen.)

You can get help with this project and find info on the software that runs on the ESP by joining the Game Boy Camera Club discord server