Show HN: PaperMono, e-ink fridge magnet shopping list with mobile web page

The PaperMono project transforms an e-paper device, the M5Stack PaperMono, into a fridge-based shopping list that syncs with a mobile web app. The device consists of an ESP32-S3 board with a 3.97 inch 480×800 e-paper touchscreen and is controlled by a small server and mobile web interface. Each item can be selected, ticked off or added to the list via a touchscreen interface or a connected phone.

The firmware for the device is open-source and written in C++, with about 2,400 lines of code. The device displays the shopping list organized by aisle in the order you walk through the store. Items added from the phone are automatically sorted into the correct aisle by the server, which uses Claude for new items.

The server, built with FastAPI, stores the shopping list and keeps track of which aisle each item belongs to. The device can be set up and run on a personal computer using PlatformIO and a PaperMono device that is connected over USB-C. The firmware and design notes are available under the GNU General Public License v3.0. While the PaperMono device works, it is not a commercial product, and there are some limitations, such as no Wi-Fi setup on the device, no authentication on the server, and only one PaperMono device tested.