ESP32-S3 Yet Another Sketchpad

A demo project for ESP32-S3 using LVGL to implement a sketchpad on a 320 x 240 TFT display.

This is a sibling project to YetAnotherStockPriceTracker and uses the same hardware.

Almost 90% of the code is referenced from lv_100ask_sketchpad, but updated for LVGL v9.2.2 and fixed for compatibility with ESP32-S3.

Project Core Values

For learning purposes.
The implementation is kept simple and straightforward.
No fancy stuff, make it work.

How This Project May Help You

If you want LVGL to use external PSRAM for large buffers, add the following to your platformio.ini. This lets LVGL use the standard C memory allocation API. When the allocated memory size is >4k, it will automatically use external PSRAM by default. This works with LVGL v9.2.2 and PlatformIO ESP32 Arduino framework (v2.0.5?).
1
-D 'LV_USE_STDLIB_MALLOC=LV_STDLIB_CLIB'
Espressif and PlatformIO are no longer collaborating, so PlatformIO does not support ESP32 Arduino framework versions >v2.0.xx. If you want to use the latest ESP32 Arduino framework (>v3), please use the Arduino IDE or the PIO Arduino VS Code extension.

Reference: Using ESP-IDF v5.x with Arduino on ESP32S3

Screenshots & Demo

Features

Simple sketchpad to draw on the screen
Button to clear the screen
Button to change the line width

Development Timeline

Date	Milestone/Note
2025-07-16	Project started
2025-07-21	v1 release

Getting Started

Prerequisites

VS Code with the PlatformIO extension
ESP32-S3 board + 2.8” TFT LCD
- Hardware purchased from Taobao. More info: ESP32-LVGL开发板
  
  Note: This dev board is not recommended due to hardware issues. It may reset automatically, especially when connected to a PC.
- ESP32-S3-N8R8
- LCD Driver: ST7989, 320 x 240 pixels
- Touch Driver: XPT2046

Building & Flashing

Clone this repository:

1	git clone https://github.com/tommokmok/esp32s3_YetAnotherSketchpad

Open the project in PlatformIO (VS Code).
Build and upload to your ESP32-S3 board.

File Structure

All libraries are placed in the local lib/ directory for convenience.

Pros:

No need to download libraries from the web when opening the project for the first time.
You can modify the source if you need specific functions.

Cons:

Larger repository size.

esp32s3_YetAnotherSketchpad/

├── lib/                            # External and user libraries
│   ├── lvgl/                       # LVGL graphics library (if added locally)
│   ├── LovyanGFX/                  # LovyanGFX display library (if added locally)
│   ├── hal/                        # Hardware Abstraction Layer (display, touch, etc.)
│   ├── appController/              # Application controller logic (state management, UI flow)
│   └── sketchpad/                  # Sketchpad implementation (drawing logic, UI components)
├── src/                            # Source code
│   ├── main.cpp                    # Main application entry point
│   └── ...                         # Other source files
├── platformio.ini                  # PlatformIO project configuration
├── README.md                       # This documentation

lib/lvgl/: LVGL graphics library (added locally).
lib/LovyanGFX/: LovyanGFX display library (added locally).
lib/hal/: Hardware Abstraction Layer for display, touch, and other peripherals.
lib/appController/: Application controller logic, such as state management and UI flow.
lib/sketchpad/: Sketchpad UI implementation.
src/main.cpp: Main application logic, including LVGL initialization and sketchpad setup.

Note: If you install libraries via the PlatformIO Library Manager, they will be managed automatically. If you add libraries manually, place them in the lib/ directory as shown above.

Implementation Details

1. Porting from 100ask code

The original source code is available at: https://github.com/100askTeam/lv_lib_100ask/tree/master/src/lv_100ask_sketchpad.

The main tasks were porting the code to the current hardware and updating it for LVGL v9.2.2.

Note: LVGL v9.1 does not work for this example, nothing will be shown on the canvas.

Issues while porting to the ESP32-S3 dev board

"error: field 'img' has incomplete type"
- This occurs because the compiler can’t find some struct definitions.
- Solution: Add the following include for internal definitions, especially if you are customizing widgets:
  1
  #include "lvgl/src/lvgl_private.h"
No colorwheel in lvgl >v9.0
- The colorwheel widget was removed in LVGL v9.0 and above. Disable related functions.
- See: https://github.com/lvgl/lvgl/issues/4429#issuecomment-2051520229

'dram0_0_seg' overflowed

The sketchpad needs a canvas object and buffer, which requires 240x320x2 bytes.
PlatformIO uses ESP-IDF v4.4 by default, which lacks some PSRAM features.
Add the following definition in platformio.ini to use standard C malloc for memory allocation. When the allocation is >1k, it will use external RAM by default:
1
-D 'LV_USE_STDLIB_MALLOC=LV_STDLIB_CLIB'

Default SDK config location on Windows:

// The default sdkconfig location in Windows
%homepath%\.platformio\packages\framework-arduinoespressif32\tools\sdk\esp32s3

// Default PSRAM usage definitions
CONFIG_SPIRAM_USE_MALLOC=y
CONFIG_SPIRAM_MALLOC_ALWAYSINTERNAL=4096

Customization

If you have different LCD or touch hardware, update the lvgl and LovyanGFX configurations accordingly.

For LVGL, add configuration options in platformio.ini.
For LovyanGFX, edit include/custom_disp.hpp.

License

MIT

Embedded Projects

ESP32-S3 lvgl: YetAnotherSketchpad 2025