E-ink (E-paper) Display Functionality Introduction
Paper-pi is a project that uses a 7.5-inch E-ink display to show various useful information, such as news, weather, cryptocurrency prices, subway status, and daily words. It utilizes low-power E-ink technology, allowing the screen to persistently display images without continuous power supply, showcasing great application potential.
This display employs network technology to obtain various information such as news and finance, and can present interesting content on the screen through a timed refresh feature.
Hardware List
The hardware components used in the Paper-pi project include:
| Hardware Component | Quantity |
| Raspberry Pi Zero Wireless | 1 |
| Sleepy Pi 2 | 1 |
| 7.5-inch E-ink Display | 1 |
| 5V Boost/Buck Voltage Regulator S9V11F5 | 1 |
| 2000mAh Lithium Polymer Battery Pack | 1 |
Building Method
The assembly of Paper-pi includes the setup of hardware components and software programs. First, a 7.5-inch E-ink screen from Waveshare was selected, along with a Raspberry Pi Zero as the mainboard. To maximize battery life, a Sleepy Pi 2 was used, which is an additional board for Raspberry Pi power management.
The battery is a 2000mAh lithium polymer battery from Adafruit, and a custom frame was used to assemble all the hardware components together. Since the battery outputs 3.7 volts and the Sleepy Pi requires 5 volts input, a voltage regulator was used to step up the voltage to 5 volts.
On the software side, JavaScript was chosen as the programming language to write a Node application to fetch the required data and generate bitmap images to be displayed on the screen. The project displays the following data: news headlines, subway status, daily words (sourced from OED), cryptocurrency prices, and weather conditions. The node-canvas library was used to generate images, along with a custom Shapely library to abstract the complexities related to the canvas.
During the assembly process, several challenges were encountered, such as conflicts between the screen’s GPIO pins and those of the Sleepy Pi, leading to noticeable issues. Ultimately, the original project author resolved this by updating the screen code. Although the HAT could not be directly inserted into the GPIO pins, it could be addressed through separate wiring.
The development board powers on for 2.5 minutes every 6 hours. This means the board is powered on for 10 minutes daily, and given the battery capacity of 2000mAh, this could potentially allow the e-paper display to last for about 90 days.
The original project creator is very satisfied with the project’s outcome, placing Paper-pi in the kitchen to quickly glance at news headlines and weather forecasts each morning before leaving home. The daily word feature is also a nice addition.
Conclusion
This device is very low-key; it looks like a framed piece of paper, has no backlight, and makes no sound. It simply sits quietly in the corner, automatically updating itself throughout the day with minimal interaction required, only needing an occasional glance. The successful construction of Paper-pi relies on using low-power screen technology combined with intelligence analysis and cutting-edge technology, along with continuously updated news information, making it a convenient product.
Project Address: https://github.com/lukehaas/paper-pi
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