E-paper or e-ink displays mimic the appearance of ink on paper, making it suitable for reading. These displays provide a wider viewing angle, and the e-paper display is easily visible in direct sunlight without the image appearing to fade. Most e-paper displays today are based on ESP32 WiFi with touchscreens and additional Bluetooth connectivity. Earlier, we have covered a similar e-ink display Inkplate 6PLUS. It is an open-source, based on Wi-Fi-enabled ESP32 board with a recycled 6.0-inch e-paper display featuring a touchscreen.
Rohit & Prasad, two young engineers from India, recently introduced paperd.ink. It is a 4.2 inch simple and elegant e-paper development board. The classic e-paper display allows you to focus on your work peacefully. The board can display calendars, weather, to-do lists, notifications, images, art pieces, and much more. The design is open-source, which means you can customize its enclosure, integrate it with custom APIs and tailor it according to your needs.
paperd.ink display specifications:
- ESP32-WROOM-32 module
- FCC/CE certified WiFi & Bluetooth for connectivity
- 4.2″ monochrome e-paper display
- <20uA current consumption in sleep mode
- CP2104 USB-UART converter onboard for programming
- MicroSD card slot for storing images, files, etc
- Piezo buzzer for notifications and alerts
- 4x tactile buttons for user input
- Battery charger circuit to keep it completely wireless
- Extension header for interfacing and expanding capabilities
ESP32-WROOM-32 microcontroller is at the core of this e-paper development board. It is one of the most popular microcontrollers as it is a complete standalone system. It can be programmed using the micro USB connection and is supported by Arduino, Micropython, and ESP-IDF. It can interface with other systems to provide WiFi and Bluetooth functionality through its SPI / SDIO or I2C / UART interfaces. It features a dual-core processor with an adjustable CPU clock frequency from 80 MHz to 240 MHz. The chip has a low-power co-processor that can be used instead of the CPU to save power while performing tasks that do not require much computing power. It has 520 KB of on-chip SRAM and an integrated 4 MB SPI flash memory. It supports WiFi 802.11 b/g/n protocols as well as Bluetooth v4.2 BR/EDR and BLE.
The 4.2-inch monochrome e-paper display has a resolution of 400 x 300 (DPI: 120). It supports the SPI interface. The e-paper display features a full refresh of 3s and has added support for a partial refresh.
In the latest version of paperd.ink, the LDO is changed to XC6220B331MR-G, which has a lower quiescent current. These revisions helped reduce the sleep current. The sleep current is currently well below 20uA. You can charge it in a single go and use it for months.
The board consists of the following external interfaces:
- UART, SPI, and I2C so you can add external sensors and modules. This makes the board extendable.
- 8 I/O for controlling any output and receiving any input.
- Disable ESP32 module using ESP_EN pin to reduce power consumption.
- Disable the entire board using the LDO_EN pin and have virtually no current consumed by the board.
The PCB measures 92.1 x 78.1 mm, and the 3D-printed enclosure is 98 x 82 x 16 mm. The enclosure comes with a stand and is 3D printed using the SLA process in ABS white material. The display is available with enclosure and without enclosure.
The KiCAD design files (schematics/PCB layout), STEP files for the 3D enclosure, and an Arduino sample are available on Github.
About the crowdfunding campaign
Engineers Prasad Khake and Rohit Gujarathi launched the crowdfunding campaign on Indiegogo for Paperd.ink and evinced interests from multiple industry stakeholders for pioneering India’s first e-paper display platform with open-source technology. The news raised over 25 percent of the intended capital needs and went viral on niche communities including Hacker News, subreddits, Facebook groups and received orders from the United States, Brazil, Israel, India, Germany, France, Spain, and United Kingdom.