While still, and perhaps forever, something of a niche item, ePaper displays are an intriguing concept. Generally black-and-white, or perhaps also red if you’re lucky, they’re great for reading, and only use power when updating what is shown. A very slow refresh rate makes this type of display a poor choice for dynamic content, but they’re very useful with e-book readers and sometimes smartwatches.
If you’d like an easy way to use one of these devices as a sort of e-Post-it note, look no further than the Papyr Nordic nRF52840 display from Electronut Labs. This device comes ready to connect to Android smartphones via BLE (Bluetooth Low Energy), and allows you to send images or handwritten notes to its screen. It the device can also receive data via MQTT if you so prefer.
One notable stat on the listing is that when advertising and not connected, the device draws a mere 22 micro amps of current. This means that the device should theoretically run for several years between battery changes, making it a great passive information display. Alternatively, the device can be programmed to your liking, and a dev kit is available with debugging and programming accessories, a battery, and laser-cut enclosure if you want to go further.
