A new open-source project turns the M5Stack PaperMono e-paper device into a household shopping list that can remain on a refrigerator while family members add items from their phones. The build combines custom device firmware, a FastAPI server and a mobile-friendly web interface.
The PaperMono hardware uses an ESP32-S3 processor with a 3.97-inch, 480-by-800-pixel e-paper touchscreen. On the device, the application groups shopping items by aisle and can arrange those groups in the order a user normally moves through a store. Items can be checked off by touching the display, and an on-screen keyboard allows direct entry. Other household members can use the accompanying web page instead.
A small server sits between the phone and the display, storing the shared list and remembering which aisle corresponds to each item. Users first configure their store's aisles through the web interface. An optional feature can use Anthropic's Claude to assign newly entered products to an aisle, but that service is not required for the basic list.
The repository contains about 2,400 lines of C++ firmware and is presented both as a working application and as a relatively compact starting point for other PaperMono projects. Installation requires PlatformIO and a USB-C connection to the device. The documentation tells users to back up the unit's flash before installing because it contains factory calibration information specific to that device.
The creator, Seamus Cawley, is explicit about the project's boundaries. It runs on one device in his home and is not a commercial product. Only the PaperMono C153 has been tested. Wi-Fi credentials must be compiled into the firmware, and the server does not provide its own authentication. The documentation therefore advises keeping it on a local network or placing it behind an authenticating reverse proxy.
Parts of the board support, touchscreen and e-paper drivers, keyboard layout and visual components were adapted from MonoMesh, an independent firmware project for the same hardware. PaperMono Shopping List is released under the GNU General Public License version 3, matching the license of the work from which those components were derived.
The project illustrates a practical strength of e-paper: a list can remain visible in a familiar physical location without behaving like a conventional glowing tablet. Its local-first design and openly stated limitations also make the tradeoffs clear. Prospective users need compatible hardware, comfort with firmware installation and a secure way to operate the server; this is a do-it-yourself build, not an appliance ready for general consumers.
