DoodlePi V2: a Raspberry Pi Pico Pixel Art Drawing Toy

DIY pixel art gadget inspired from Etch A Sketch: draw, erase, and create retro-style art. Programmed using Arduino IDE.

Feb 27, 2026

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GPL3+

Games

Kids

Toys

Devices & Components

Li-Ion Battery 1000mAh

Raspberry Pi Pico

DoodlePi PCB (Gerber files available below)

Generic push button

JST Connectors

Slide Switch

1,3" OLED Display SH1106 128x64 I2C

TP4056 with battery protection

Hardware & Tools

Soldering iron (generic)

Software & Tools

Arduino IDE

Project description

Code

DoodlePi

cpp

Upload this code using Arduino IDE.

1/*
2* Project Name: DoodlePi
3* Designed For: Raspberry Pi Pico/Pico W
4*
5*
6* License: GPL3+
7* This project is licensed under the GNU General Public License v3.0 or later.
8* You are free to use, modify, and distribute this software under the terms
9* of the GPL, as long as you preserve the original license and credit the original
10* author. For more details, see <https://www.gnu.org/licenses/gpl-3.0.en.html>.
11*
12* Copyright (C) 2025 Ameya Angadi
13*
14* Code Created And Maintained By: Ameya Angadi
15* Last Modified On: November 11, 2025
16* Version: 2.0.0
17*
18*/
19
20#include <Wire.h>
21#include <Adafruit_GFX.h>
22#include <Adafruit_SH110X.h>
23
24#define OLED_I2C_ADDRESS 0x3C
25#define DISPLAY_WIDTH 128
26#define DISPLAY_HEIGHT 64
27#define OLED_RESET -1
28
29Adafruit_SH1106G display = Adafruit_SH1106G(DISPLAY_WIDTH, DISPLAY_HEIGHT, &Wire, OLED_RESET);
30
31const unsigned char Splash_Screen[] PROGMEM = {
32// "DoodlePi", 128x64px
330xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
340x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
350x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
360x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
370x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
380x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
390x80, 0x00, 0x00, 0x07, 0xf8, 0x00, 0x00, 0x00, 0xe7, 0x00, 0x07, 0xf8, 0x00, 0x00, 0x00, 0x01,
400x80, 0x00, 0x00, 0x07, 0xfc, 0x00, 0x00, 0x00, 0xe7, 0x00, 0x07, 0xfc, 0x00, 0x00, 0x00, 0x01,
410x80, 0x00, 0x00, 0x07, 0xfc, 0x00, 0x00, 0x00, 0xe7, 0x00, 0x07, 0xfd, 0xc0, 0x00, 0x00, 0x01,
420x80, 0x00, 0x00, 0x07, 0x1c, 0x00, 0x00, 0x00, 0xe7, 0x00, 0x07, 0x1d, 0xc0, 0x00, 0x00, 0x01,
430x80, 0x00, 0x00, 0x07, 0x1c, 0x00, 0x00, 0x00, 0xe7, 0x00, 0x07, 0x1d, 0xc0, 0x00, 0x00, 0x01,
440x80, 0x00, 0x00, 0x07, 0x1c, 0x00, 0x00, 0x00, 0xe7, 0x00, 0x07, 0x1c, 0x00, 0x00, 0x00, 0x01,
450x80, 0x00, 0x00, 0x07, 0x1c, 0xfc, 0x3f, 0x0f, 0xe7, 0x1f, 0x87, 0x1d, 0xc0, 0x00, 0x00, 0x01,
460x80, 0x00, 0x00, 0x07, 0x1d, 0xfe, 0x7f, 0x9f, 0xe7, 0x3f, 0xc7, 0x1d, 0xc0, 0x00, 0x00, 0x01,
470x80, 0x00, 0x00, 0x07, 0x1d, 0xce, 0x73, 0x9c, 0xe7, 0x39, 0xc7, 0xfd, 0xc0, 0x00, 0x00, 0x01,
480x80, 0x00, 0x00, 0x07, 0x1d, 0xce, 0x73, 0x9c, 0xe7, 0x39, 0xc7, 0xfd, 0xc0, 0x00, 0x00, 0x01,
490x80, 0x00, 0x00, 0x07, 0x1d, 0xce, 0x73, 0x9c, 0xe7, 0x39, 0xc7, 0xf9, 0xc0, 0x00, 0x00, 0x01,
500x80, 0x00, 0x00, 0x07, 0x1d, 0xce, 0x73, 0x9c, 0xe7, 0x3f, 0xc7, 0x01, 0xc0, 0x00, 0x00, 0x01,
510x80, 0x00, 0x00, 0x07, 0x1d, 0xce, 0x73, 0x9c, 0xe7, 0x3f, 0xc7, 0x01, 0xc0, 0x00, 0x00, 0x01,
520x80, 0x00, 0x00, 0x07, 0x1d, 0xce, 0x73, 0x9c, 0xe7, 0x38, 0x07, 0x01, 0xc0, 0x00, 0x00, 0x01,
530x80, 0x00, 0x00, 0x07, 0x1d, 0xce, 0x73, 0x9c, 0xe7, 0x39, 0xc7, 0x01, 0xc0, 0x00, 0x00, 0x01,
540x80, 0x00, 0x00, 0x07, 0xfd, 0xce, 0x73, 0x9c, 0xe7, 0x39, 0xc7, 0x01, 0xc0, 0x00, 0x00, 0x01,
550x80, 0x00, 0x00, 0x07, 0xfd, 0xfe, 0x7f, 0x9f, 0xe7, 0x3f, 0xc7, 0x01, 0xc0, 0x00, 0x00, 0x01,
560x80, 0x00, 0x00, 0x07, 0xf8, 0xfc, 0x3f, 0x0e, 0xe7, 0x1f, 0x87, 0x01, 0xc0, 0x00, 0x00, 0x01,
570x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
580x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
590x80, 0x00, 0x00, 0x7f, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xfe, 0x00, 0x00, 0x01,
600x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
610x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x11, 0x00, 0x0e, 0x38, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
620x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x11, 0x00, 0x0a, 0x28, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
630x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x0a, 0x7a, 0xc2, 0x28, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
640x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x0a, 0x4b, 0x46, 0x28, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
650x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x0a, 0x7a, 0x08, 0x28, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
660x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 0x42, 0x08, 0x28, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
670x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 0x7a, 0x0e, 0xb8, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
680x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
690x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x3f, 0xff, 0xff, 0xfc, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
700x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
710x83, 0xff, 0xff, 0xff, 0xff, 0xc0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
720x82, 0x00, 0x00, 0x00, 0x00, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
730x82, 0x00, 0x00, 0x00, 0x00, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
740x82, 0x00, 0x00, 0x00, 0x18, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
750x82, 0x00, 0x00, 0x00, 0x24, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
760x82, 0x00, 0x00, 0x00, 0x24, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
770x82, 0x00, 0x80, 0x00, 0x18, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
780x82, 0x01, 0xc0, 0x00, 0x00, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
790x82, 0x03, 0x60, 0x00, 0x00, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
800x82, 0x06, 0xf0, 0x00, 0x40, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
810x82, 0x0d, 0xf8, 0x00, 0xe0, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
820x82, 0x1b, 0xfc, 0x01, 0xb0, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
830x82, 0x37, 0xfe, 0x03, 0x78, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
840x82, 0x6f, 0xff, 0x06, 0xfc, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
850x82, 0xdf, 0xff, 0x8d, 0xfe, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
860x83, 0xbf, 0xff, 0xdb, 0xff, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
870x83, 0xff, 0xff, 0xf7, 0xff, 0xc0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
880x83, 0xff, 0xff, 0xff, 0xff, 0xc0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
890x83, 0xff, 0xff, 0xff, 0xff, 0xc0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
900x83, 0xff, 0xff, 0xff, 0xff, 0xc0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x13, 0xed, 0x49,
910x83, 0xff, 0xff, 0xff, 0xff, 0xc0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x2a, 0xa9, 0x55,
920x83, 0xff, 0xff, 0xff, 0xff, 0xc0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x3a, 0xad, 0xdd,
930x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x2a, 0xa8, 0x55,
940x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x2a, 0xad, 0xd5,
950x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
960xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff
97};
98
99// Button pins
100const int BtnPenControl = 10;
101const int BtnEraser = 11;
102const int BtnPenDown = 12;
103const int BtnPenLeft = 13;
104const int BtnPenRight = 14;
105const int BtnPenUp = 15;
106
107int x = 2, y = 2; // Start inside the border
108bool penDown = true;
109bool cursorVisible = true;
110unsigned long lastToggleTime = 0;
111const int debounceDelay = 300;
112unsigned long lastCursorBlink = 0;
113const int blinkInterval = 500;
114
115// Canvas state tracker (true = drawn)
116bool canvas[DISPLAY_WIDTH][DISPLAY_HEIGHT] = { false };
117
118void drawBorder() {
119display.drawRect(0, 0, DISPLAY_WIDTH, DISPLAY_HEIGHT, SH110X_WHITE);
120}
121
122void drawSquare(int x, int y, bool color) {
123for (int dx = 0; dx < 2; dx++) {
124for (int dy = 0; dy < 2; dy++) {
125if (x + dx < DISPLAY_WIDTH && y + dy < DISPLAY_HEIGHT) {
126display.drawPixel(x + dx, y + dy, color ? SH110X_WHITE : SH110X_BLACK);
127}
128}
129}
130}
131
132void updateCanvasState(int x, int y, bool state) {
133for (int dx = 0; dx < 2; dx++) {
134for (int dy = 0; dy < 2; dy++) {
135if (x + dx < DISPLAY_WIDTH && y + dy < DISPLAY_HEIGHT) {
136canvas[x + dx][y + dy] = state;
137}
138}
139}
140}
141
142bool squareIsEmpty(int x, int y) {
143for (int dx = 0; dx < 2; dx++) {
144for (int dy = 0; dy < 2; dy++) {
145if (canvas[x + dx][y + dy]) return false;
146}
147}
148return true;
149}
150
151void setup() {
152
153pinMode(BtnPenControl, INPUT_PULLUP);
154pinMode(BtnEraser, INPUT_PULLUP);
155pinMode(BtnPenUp, INPUT_PULLUP);
156pinMode(BtnPenDown, INPUT_PULLUP);
157pinMode(BtnPenLeft, INPUT_PULLUP);
158pinMode(BtnPenRight, INPUT_PULLUP);
159pinMode(LED_BUILTIN, OUTPUT);
160
161digitalWrite(LED_BUILTIN, HIGH);
162display.begin(OLED_I2C_ADDRESS, true);
163display.clearDisplay();
164display.setTextColor(SH110X_WHITE);
165display.setCursor(0, 0);
166display.drawBitmap(0, 0, Splash_Screen, 128, 64, SH110X_WHITE);
167display.display();
168delay(3000);
169digitalWrite(LED_BUILTIN, LOW);
170display.clearDisplay();
171drawBorder();
172display.display();
173
174}
175
176void loop() {
177// Toggle pen status
178if (digitalRead(BtnPenControl) == LOW && digitalRead(BtnEraser) == HIGH) {
179if (millis() - lastToggleTime > debounceDelay) {
180penDown = !penDown;
181lastToggleTime = millis();
182}
183}
184
185// Clear screen if both buttons are pressed
186if (digitalRead(BtnPenControl) == LOW && digitalRead(BtnEraser) == LOW) {
187x = 2;
188y = 2;
189penDown = true;
190display.clearDisplay();
191drawBorder();
192memset(canvas, 0, sizeof(canvas));
193display.display();
194delay(200);
195return;
196}
197
198// Blinking cursor if pen is up and square is empty
199if (!penDown && millis() - lastCursorBlink > blinkInterval) {
200cursorVisible = !cursorVisible;
201lastCursorBlink = millis();
202
203if (squareIsEmpty(x, y)) {
204drawSquare(x, y, cursorVisible);
205display.display();
206}
207}
208
209// Movement logic
210int newX = x;
211int newY = y;
212
213if (digitalRead(BtnPenUp) == LOW && y > 2) newY--;
214if (digitalRead(BtnPenDown) == LOW && y < DISPLAY_HEIGHT - 4) newY++;
215if (digitalRead(BtnPenLeft) == LOW && x > 2) newX--;
216if (digitalRead(BtnPenRight) == LOW && x < DISPLAY_WIDTH - 4) newX++;
217
218if (newX != x || newY != y) {
219// Erase old cursor if blinking and not over drawn pixels
220if (!penDown && squareIsEmpty(x, y)) {
221drawSquare(x, y, false);
222}
223
224x = newX;
225y = newY;
226
227if (penDown) {
228if (digitalRead(BtnEraser) == LOW) {
229// Erase mode
230drawSquare(x, y, false);
231updateCanvasState(x, y, false);
232} else {
233// Draw mode
234drawSquare(x, y, true);
235updateCanvasState(x, y, true);
236}
237} else {
238// Show cursor
239if (squareIsEmpty(x, y)) {
240drawSquare(x, y, true);
241cursorVisible = true;
242lastCursorBlink = millis();
243}
244}
245
246display.display();
247delay(50);
248}
249}

/*
* 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: November 11, 2025
* Version: 2.0.0
*
*/

#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,
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0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x0a, 0x7a, 0xc2, 0x28, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
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0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x0a, 0x7a, 0x08, 0x28, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 0x42, 0x08, 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, 0x00, 0x01,
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0x82, 0x6f, 0xff, 0x06, 0xfc, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
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0x83, 0xbf, 0xff, 0xdb, 0xff, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
0x83, 0xff, 0xff, 0xf7, 0xff, 0xc0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
0x83, 0xff, 0xff, 0xff, 0xff, 0xc0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
0x83, 0xff, 0xff, 0xff, 0xff, 0xc0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
0x83, 0xff, 0xff, 0xff, 0xff, 0xc0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x13, 0xed, 0x49,
0x83, 0xff, 0xff, 0xff, 0xff, 0xc0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x2a, 0xa9, 0x55,
0x83, 0xff, 0xff, 0xff, 0xff, 0xc0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x3a, 0xad, 0xdd,
0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x2a, 0xa8, 0x55,
0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x2a, 0xad, 0xd5,
0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff
};

// Button pins
const int BtnPenControl = 10;
const int BtnEraser = 11;
const int BtnPenDown = 12;
const int BtnPenLeft = 13;
const int BtnPenRight = 14;
const int BtnPenUp = 15;

int x = 2, y = 2; // Start inside the border
bool penDown = true;
bool cursorVisible = true;
unsigned long lastToggleTime = 0;
const int debounceDelay = 300;
unsigned long lastCursorBlink = 0;
const int blinkInterval = 500;

// Canvas state tracker (true = drawn)
bool canvas[DISPLAY_WIDTH][DISPLAY_HEIGHT] = { false };

void drawBorder() {
display.drawRect(0, 0, DISPLAY_WIDTH, DISPLAY_HEIGHT, SH110X_WHITE);
}

void drawSquare(int x, int y, bool color) {
for (int dx = 0; dx < 2; dx++) {
for (int dy = 0; dy < 2; dy++) {
if (x + dx < DISPLAY_WIDTH && y + dy < DISPLAY_HEIGHT) {
display.drawPixel(x + dx, y + dy, color ? SH110X_WHITE : SH110X_BLACK);
}
}
}
}

void updateCanvasState(int x, int y, bool state) {
for (int dx = 0; dx < 2; dx++) {
for (int dy = 0; dy < 2; dy++) {
if (x + dx < DISPLAY_WIDTH && y + dy < DISPLAY_HEIGHT) {
canvas[x + dx][y + dy] = state;
}
}
}
}

bool squareIsEmpty(int x, int y) {
for (int dx = 0; dx < 2; dx++) {
for (int dy = 0; dy < 2; dy++) {
if (canvas[x + dx][y + dy]) return false;
}
}
return true;
}

void setup() {

pinMode(BtnPenControl, INPUT_PULLUP);
pinMode(BtnEraser, INPUT_PULLUP);
pinMode(BtnPenUp, INPUT_PULLUP);
pinMode(BtnPenDown, INPUT_PULLUP);
pinMode(BtnPenLeft, INPUT_PULLUP);
pinMode(BtnPenRight, INPUT_PULLUP);
pinMode(LED_BUILTIN, OUTPUT);

digitalWrite(LED_BUILTIN, HIGH);
display.begin(OLED_I2C_ADDRESS, true);
display.clearDisplay();
display.setTextColor(SH110X_WHITE);
display.setCursor(0, 0);
display.drawBitmap(0, 0, Splash_Screen, 128, 64, SH110X_WHITE);
display.display();
delay(3000);
digitalWrite(LED_BUILTIN, LOW);
display.clearDisplay();
drawBorder();
display.display();

}

void loop() {
// Toggle pen status
if (digitalRead(BtnPenControl) == LOW && digitalRead(BtnEraser) == HIGH) {
if (millis() - lastToggleTime > debounceDelay) {
penDown = !penDown;
lastToggleTime = millis();
}
}

// Clear screen if both buttons are pressed
if (digitalRead(BtnPenControl) == LOW && digitalRead(BtnEraser) == LOW) {
x = 2;
y = 2;
penDown = true;
display.clearDisplay();
drawBorder();
memset(canvas, 0, sizeof(canvas));
display.display();
delay(200);
return;
}

// Blinking cursor if pen is up and square is empty
if (!penDown && millis() - lastCursorBlink > blinkInterval) {
cursorVisible = !cursorVisible;
lastCursorBlink = millis();

if (squareIsEmpty(x, y)) {
drawSquare(x, y, cursorVisible);
display.display();
}
}

// Movement logic
int newX = x;
int newY = y;

if (digitalRead(BtnPenUp) == LOW && y > 2) newY--;
if (digitalRead(BtnPenDown) == LOW && y < DISPLAY_HEIGHT - 4) newY++;
if (digitalRead(BtnPenLeft) == LOW && x > 2) newX--;
if (digitalRead(BtnPenRight) == LOW && x < DISPLAY_WIDTH - 4) newX++;

if (newX != x || newY != y) {
// Erase old cursor if blinking and not over drawn pixels
if (!penDown && squareIsEmpty(x, y)) {
drawSquare(x, y, false);
}

x = newX;
y = newY;

if (penDown) {
if (digitalRead(BtnEraser) == LOW) {
// Erase mode
drawSquare(x, y, false);
updateCanvasState(x, y, false);
} else {
// Draw mode
drawSquare(x, y, true);
updateCanvasState(x, y, true);
}
} else {
// Show cursor
if (squareIsEmpty(x, y)) {
drawSquare(x, y, true);
cursorVisible = true;
lastCursorBlink = millis();
}
}

display.display();
delay(50);
}
}

Downloadable files

Schematics

Use this Schematics for reference.

DoodlePi Schematics.png