Eric Nam's Espressif ESP32 Digital Photo Frame Packs a Smart Seven-Color ePaper Display Panel
A low-power seven-color ePaper display delivers an energy-efficient automatically-updating photo frame in Nam's latest build.
Maker Eric Nam has built a low-power daylight-readable digital picture frame, powered by an Espressif ESP32-S3 microcontroller — but, in a twist, has opted for a seven-color ePaper display that delivers a long battery life without having to drop down to grayscale imagery.
"This displays image data on a 5.65" seven-color ePaper [display]," Nam explains of his creation. "The good thing about the ePaper [display] is that it only consumes power when updating the screen, and it can keep the current screen even when the power is cut off. That's why it's very advantageous to [use in] a battery-powered system."
Electrophoretic ePaper displays, in which physical globules of ink are moved towards or away from the upper layer of the screen, are sunlight-readable, low-power, but have their downsides — including a refresh rate which is, at worst, measured in seconds-per-frame rather than frames-per-second and the fact that the majority on the market are black and white. That's not the case for Nam's chosen panel, a Seeed Studio 5.65" display that delivers a seven-color palette — albeit at the cost of a 22-second refresh time.
The display is driven using Seeed XIAO ESP32S3, a compact microcontroller board based on the Espressif ESP32-S3. A Raspberry Pi running a Flask server transmits image data to the ESP32, which then puts them on the screen — after they're resized to the display's native resolution and processed down to seven colors. It's this last step that makes Nan's display pop: using Floyd-Steinberg dithering, the illusion of more colors is created and the quality of the photos maintained.
"ePaper digital frames are very interesting," Nam concludes. "I'd like to see faster screen refresh rates and more colors displayed […] at a reasonable price."
The project is documented in the video above and on Nam's YouTube channel, with more information available alongside the MIT licensed source code on the project's GitHub repository.