Step 1: Make the Breadboard Connections & I2C Handshake

The DoodlePi functions as a discrete digital canvas, mapping binary input states directly onto an I2C-based SH1106 array. The primary protocol links the OLED natively to the Raspberry Pi Pico's RP2040 chip, aligning pull-up configurations for stable communication.

Connect your 1.3-inch SH1106 OLED module to the Raspberry Pi Pico using the circuit diagram shared above.

VCC → VSYS (Pico pin 39)
GND → GND (Pico pin 38)
SDA → GP4 (Pico pin 6)
SCL → GP5 (Pico pin 7)

Step 2: Assemble the Buttons on a Perf Board (Optional) & Haptic Matrix Consolidation

A mechanical switch matrix is deployed onto a perfboard to translate haptic interactions into logic states. The layout maps standard XY-axis Cartesian vectors (Up, Down, Left, Right). The auxiliary controls implement a Pen-Toggle state machine modifier and a Boolean Eraser mode. Grounding routines tie directly back to the GPIO headers via standard jumper interfaces.

Arrange the six buttons in a way that feels natural to hold, similar to a game controller layout.

Four buttons can be used for Up, Down, Left, Right, one for Pen Toggle (Pen up/down), and one for Clear/Eraser mode.

Solder each button to the perf board, then connect them to the Pico with jumper wires according to the previous circuit diagram.

I have particularly soldered the buttons in a such a way that allows me to use it like a keypad module.

Note: This step is completely optional and the button connections can be made on breadboard for simplicity.

Step 3: Upload the Code & Flash Memory Allocation

Utilizing the Arduino IDE Workspace, the Adafruit GFX logic bridges raw pixel rendering to abstract commands. The provided C++ sketch initializes a boolean penDown state tracker, constantly updating local RAM with a sequential array that mirrors the screen's layout.

Use Arduino IDE to upload the provided C++ code.

Make sure to install Earle Philhower's Pico Core and required libraries. Follow this tutorial Getting Started with Raspberry Pi Pico in Arduino IDE

Required Libraries:

Adafruit GFX Library
Adafruit SH110X Library
Earle Philhower's Pico Core

Code:

/*
	* Project Name: DoodlePi
	* Designed For: Raspberry Pi Pico/Pico W
	*
	*
	* License: GPL3+
	* This project is licensed under the GNU General Public License v3.0 or later.
	* You are free to use, modify, and distribute this software under the terms
	* of the GPL, as long as you preserve the original license and credit the original
	* author. For more details, see <https://www.gnu.org/licenses/gpl-3.0.en.html>.
	*
	* Copyright (C) 2025  Ameya Angadi
	*
	* Code Created And Maintained By: Ameya Angadi
	* Last Modified On: August 15, 2025
	* Version: 1.0.0
	*
	*/
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SH110X.h>
#define OLED_I2C_ADDRESS 0x3C
#define DISPLAY_WIDTH 128
#define DISPLAY_HEIGHT 64
#define OLED_RESET -1
Adafruit_SH1106G display = Adafruit_SH1106G(DISPLAY_WIDTH, DISPLAY_HEIGHT, &Wire, OLED_RESET);
const unsigned char Splash_Screen [] PROGMEM = {
	// "DoodlePi", 128x64px
	0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
	0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
	0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
	0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
	0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
	0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
	0x80, 0x00, 0x00, 0x07, 0xf8, 0x00, 0x00, 0x00, 0xe7, 0x00, 0x07, 0xf8, 0x00, 0x00, 0x00, 0x01,
	0x80, 0x00, 0x00, 0x07, 0xfc, 0x00, 0x00, 0x00, 0xe7, 0x00, 0x07, 0xfc, 0x00, 0x00, 0x00, 0x01,
	0x80, 0x00, 0x00, 0x07, 0xfc, 0x00, 0x00, 0x00, 0xe7, 0x00, 0x07, 0xfd, 0xc0, 0x00, 0x00, 0x01,
	0x80, 0x00, 0x00, 0x07, 0x1c, 0x00, 0x00, 0x00, 0xe7, 0x00, 0x07, 0x1d, 0xc0, 0x00, 0x00, 0x01,
	0x80, 0x00, 0x00, 0x07, 0x1c, 0x00, 0x00, 0x00, 0xe7, 0x00, 0x07, 0x1d, 0xc0, 0x00, 0x00, 0x01,
	0x80, 0x00, 0x00, 0x07, 0x1c, 0x00, 0x00, 0x00, 0xe7, 0x00, 0x07, 0x1c, 0x00, 0x00, 0x00, 0x01,
	0x80, 0x00, 0x00, 0x07, 0x1c, 0xfc, 0x3f, 0x0f, 0xe7, 0x1f, 0x87, 0x1d, 0xc0, 0x00, 0x00, 0x01,
	0x80, 0x00, 0x00, 0x07, 0x1d, 0xfe, 0x7f, 0x9f, 0xe7, 0x3f, 0xc7, 0x1d, 0xc0, 0x00, 0x00, 0x01,
	0x80, 0x00, 0x00, 0x07, 0x1d, 0xce, 0x73, 0x9c, 0xe7, 0x39, 0xc7, 0xfd, 0xc0, 0x00, 0x00, 0x01,
	0x80, 0x00, 0x00, 0x07, 0x1d, 0xce, 0x73, 0x9c, 0xe7, 0x39, 0xc7, 0xfd, 0xc0, 0x00, 0x00, 0x01,
	0x80, 0x00, 0x00, 0x07, 0x1d, 0xce, 0x73, 0x9c, 0xe7, 0x39, 0xc7, 0xf9, 0xc0, 0x00, 0x00, 0x01,
	0x80, 0x00, 0x00, 0x07, 0x1d, 0xce, 0x73, 0x9c, 0xe7, 0x3f, 0xc7, 0x01, 0xc0, 0x00, 0x00, 0x01,
	0x80, 0x00, 0x00, 0x07, 0x1d, 0xce, 0x73, 0x9c, 0xe7, 0x3f, 0xc7, 0x01, 0xc0, 0x00, 0x00, 0x01,
	0x80, 0x00, 0x00, 0x07, 0x1d, 0xce, 0x73, 0x9c, 0xe7, 0x38, 0x07, 0x01, 0xc0, 0x00, 0x00, 0x01,
	0x80, 0x00, 0x00, 0x07, 0x1d, 0xce, 0x73, 0x9c, 0xe7, 0x39, 0xc7, 0x01, 0xc0, 0x00, 0x00, 0x01,
	0x80, 0x00, 0x00, 0x07, 0xfd, 0xce, 0x73, 0x9c, 0xe7, 0x39, 0xc7, 0x01, 0xc0, 0x00, 0x00, 0x01,
	0x80, 0x00, 0x00, 0x07, 0xfd, 0xfe, 0x7f, 0x9f, 0xe7, 0x3f, 0xc7, 0x01, 0xc0, 0x00, 0x00, 0x01,
	0x80, 0x00, 0x00, 0x07, 0xf8, 0xfc, 0x3f, 0x0e, 0xe7, 0x1f, 0x87, 0x01, 0xc0, 0x00, 0x00, 0x01,
	0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
	0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
	0x80, 0x00, 0x00, 0x7f, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xfe, 0x00, 0x00, 0x01,
	0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
	0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x11, 0x00, 0x04, 0x38, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
	0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x11, 0x00, 0x0c, 0x28, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
	0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x0a, 0x7a, 0xc4, 0x28, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
	0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x0a, 0x4b, 0x44, 0x28, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
	0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x0a, 0x7a, 0x04, 0x28, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
	0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 0x42, 0x04, 0x28, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
	0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 0x7a, 0x0e, 0xb8, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
	0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
	0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x3f, 0xff, 0xff, 0xfc, 0x00, 0x00, 0x00, 0x00, 0

Step 1: Make the Breadboard Connections & I2C Handshake

Step 2: Assemble the Buttons on a Perf Board (Optional) & Haptic Matrix Consolidation

Step 3: Upload the Code & Flash Memory Allocation

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