ESP32 E-Paper Digital Frame Project

This project is a digital photo frame using an ESP32 microcontroller and a 5.65” seven-color E-Paper display, optimized to display images with a 7-color palette. The ESP32 retrieves image data from a local server and displays it on the screen, with a power-saving feature that puts the ESP32 into hibernation between updates.

Project Overview

This setup is designed to efficiently display photos on an E-Paper display, which supports only a limited color palette. To achieve the best image quality, images are converted using Floyd–Steinberg dithering and a custom 7-color palette.

Hardware

[Note] I have only tested it with this display, so it may not work with other E-Paper 7-color displays.

• 5.65” Seven-Color E-Paper Display 600x448
• E-Paper Breakout Board for Seeed Studio XIAO
• Seeed Studio XIAO ESP32S3
• 1S LiPo Battery 3.7v
• Raspberry Pi 4 (for local server)

System Architecture

1.  Raspberry Pi with Flask Server:

• Hosts a simple API server that serves image data to the ESP32.
• Monitors a designated folder for new images and automatically processes them to the required format.

2.  ESP32 with E-Paper Display:

• Requests image data from the server.
• Draws the image on the E-Paper display.
• Retrieves the next wake-up interval from the server to manage its power-saving hibernation mode.

Workflow

1.  Image Conversion: New images added to the Images folder are automatically resized to 600x448 and processed using Floyd–Steinberg dithering to match the 7-color palette.
2.  Flask API: The server sends converted images in byte data format ready for display. The ESP32 requests new images and draws them on the display.
3.  Hibernation Schedule: Between 8 AM and 8 PM, the ESP32 wakes up every hour for updates. After 8 PM, it hibernates until 8 AM the following day.

ESP32 Setup

• _Test_E_Paper_5_65inch_7color: A test program for the E-Paper display.
• E-Paper_Photo_Frame: The main program to connect to the server and update the display dynamically.
  • This code stores the image data obtained from the server into PSRAM. Please change this part according to your needs.

Raspberry Pi Server Setup

[Note] The reason I used RPI here is that this is a personal local test server that is always on. You can use it on your PC as well, not just RPI.

1. Clone this repository to your Raspberry Pi.

git clone https://github.com/0015/7-Color-E-Paper-Digital-Photo-Frame.git

2.  Install the dependencies:

pip install -r requirements.txt

3.  Set up and start the Flask server:

python flask_server.py

The monitor.py script will automatically run alongside. It will watch the Images folder, resize images, apply dithering, and save the result as .h files in the h_files folder.

Flask API Endpoints

• /get-img-data: Returns the next image data in byte format.
• /status: Returns the status of sent and remaining files.
• /wakeup-interval: Returns the interval (in seconds) until the next wake-up time based on the current time.

Dependencies

• Flask: For running the API server.
• Watchdog: For monitoring file changes.
• Pillow: For image processing.
• NumPy: For handling numerical operations during image conversion.