DISPLAYS AND UIs
How to Design a Graphic User Interface on an E-Paper Display
Rich graphic user interfaces (GUIs) are everywhere, with the challenges when designing a user interface on an e-paper display (EPD)?
The challenges
A user interface should be intuitive, consistent, interactive and adaptable.
The elements of the interface should speak by themselves, with a clear distinction between passive areas such as labels or texts and active areas such as buttons. All the elements should share the same metaphor. When the user interacts, a timely feed-back enhances the user experience. Finally, the same interface should easily manage different sizes of the screens. Embedded systems bring additional challenges such as constrained memory, both RAM and Flash, limited processing capabilities and a strict power budget.
EPDs offer a limited range of colours. This leads developers to rethink the interface, simplify it and focus on its core elements. This process streamlines the user interface and provides a better user experience. “Spectra 4” EPD with black-white-red-yellow are ideal for high-impact messages, for example: black for information, yellow for warning and red for urgency.
Figure 2 – The EPD Touch Development Kit (EXT3-Touch) to explore interactive user interface
an active element, such as a button that triggers an action, from a passive element like a text that displays a value, the active elements are displayed within a frame. EPDs rely on a framebuffer to generate the image before displaying it. Because each pixel requires only one bit for black and white colours, the framebuffer is very compact, with a limited footprint on RAM. The micro-controller generates the image at optimal speed then sends it to the screen. The controller of the EPD stores the optimised waveforms for each mode to ensure an optimal image quality.
Figure 1 – A dashboard leveraging the Spectra 4 screen for high impact
When touch is added, the black and white colours EPD with embedded fast refresh is recommended. A fast refresh takes less than time threshold.
When visual feedback is not fast enough, haptic feedback offers an interesting and almost instantaneous option. To differentiate
The bi-stable nature of e-paper displays brings ultra-low power consumption. Because EPDs only require power to change the image and because EPDs maintain the image displayed with no power needed, the entire system can enter deep sleep. Contrary to other technologies such as TFT, there is no burning effect. As an example, an electronic shelf label (ESL) typically operates for more than ten years on two coin-cell batteries. EPDs are highly readable outdoors, even under direct sunlight with a special coating protecting it from the UVs; this also applies indoors, with a front-lightning and edge LEDs. Similarly, the viewing angle is very wide, texts and images crisp.
14 MARCH 2025 | ELECTRONICS FOR ENGINEERS
Pervasive Displays offers a complete rapid development kits, including hardware, software, documentation and services to drive all models of EPD from concept prototype design to product or solution roll-out. For discovering the e-paper technology, introductory kits are welcome. The EPD Development Kit (EPDK) is a self-contained kit and includes the screen, the driving board and the controller. The EPD Touch Development Kit (EPDK-Touch) targets the touch screens. When working with an EPD, users usually need to go through the process of initialising and driving the EPD to control its to output the desired text or pixels on the screen to present the expected user interface, which will be a lengthy process of research and testing. At this stage, if there is an existing graphics library that has built in and parameters, it will greatly reduce the for EPDs. It brings a large collection of fonts, monospaced and proportional, with sizes from histogram; and GUI elements, including button, checkbox, radio-buttons, switch, cursor, keyboard, label, textbox, bar-graph. Each GUI element offers different levels of
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