You can transform regular paper into almost anything – write on it, make origami or even change it into paper-mache. Similarly, e-paper is also proving to be a platform for realizing incredible and versatile projects. E-paper has amazing properties such as excellent visibility, paper like readability and very low energy consumption. That makes e-paper a perfect platform for making phones, accessories and digital signs.
Pi Supply is now offering Papirus, a display HAT supporting e-paper displays up to 2.7-inches on the Raspberry Pi or RBPi Single Board Computer. Although another e-paper HAT is also available from Percheron Electronics, Papirus is priced lower than the Percheron e-paper HAT.
According to Pi Supply, Papirus is optimized for the RBPi Models A+, B+ and the RBPi 2 Model B. However, Papirus works well with any SBC running on 3.3 or 5V logic and power, provided the SBC includes I2C and SPI interfaces. Therefore, apart from the RBPi, you can use Papirus with Arduino, BeagleBone and possibly, the RBPi-Zero.
Similar to the Percheron e-paper HAT, Papirus also offers the three options of Pervasive Display. These options include displays of 1.44-in. 128×96 pixels, 2-in. 200X96 pixels and 2.7-in. 264X176 pixels. Papirus has optional slim-line switches.
The display on Papirus is supported by on-board 32Mbit flash memory. As the display is in the form of Hardware on Top or HAT, it has the necessary EEPROM to make it plug and play with the RBPi. A battery-backed RTC allows keeping real time. The on-board digital temperature sensor and thermal watchdog provide a safeguard against unnatural temperature excursions.
Papirus interfaces with the RBPi through its GPIO connector. Pi Supply offers users an optional GPIO breakout board and an optional reset pin header for a wake on alarm with RTC. Other optional offers are a pogo pin and four slim-line switches, which the user can solder on top of the board.
Currently, one can use Papirus with rePaper, the free software offering from Pervasive. Pi Supply is planning to add enhancements above the free offering. According to Pi Supply, this could be in the form of an Easy Installer and include example scripts, which will help to push the Raspbian desktop to the e-paper screen. Another possibility is the addition of a web application for remote screen management.
Functionally, E-paper is similar to ordinary paper. When jotting down something on ordinary paper, your pen leaves well-defined lines or text. Electronic paper displays give the same crispness and high-readability of their contents. However, the method of displaying contents on an e-paper display is different from that used by Liquid Crystal Displays.
E-paper uses e-ink technology for displaying its contents. Electronic paper display is actually made up of millions of capsules within a thin film. Each capsule contains a clear fluid in which there are several tiny particles of black and white colors and with different electric charges. On each capsule are two transparent electrodes on its top and bottom sides. Applying a positive or a negative electric field to an individual electrode makes particles with the corresponding charge move to either the top or the bottom of the capsule. The surface of the e-paper display on the capsule now appears to be either black or white.