Claude Code builds a PaperMono shopping list
Seamus Cawley reports building fridge-mounted PaperMono shopping-list firmware with Claude Code, then using its synced phone and e-paper lists at home.
news.ycombinator.com
Suggested prompt
Suggested prompt written by Agents In Use, not the source author. Replace bracketed inputs and review tool permissions first.
Build a shopping-list prototype for my PaperMono using the supplied hardware notes. Reuse proven drivers with attribution, add offline edits and phone sync, and record device failures for my review.
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See placements →Evidence at a glance
Sourced account- Source author
- Seamus Cawley / seamus_c
- Original account
- Read the source ↗
- Published
- 28 Sept 2026
- Source link checked
- 15 Oct 2026
- Reported result
- Seamus Cawley reports building fridge-mounted PaperMono shopping-list firmware with Claude Code, then using its synced phone and e-paper lists at home.
- Human involvement
- Cawley directed the project and tried the device at home; he reports daily use, but no independent firmware or battery validation is supplied.
A linked account supports attribution. It does not mean we independently reproduced its result.
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How the agent did it
- Cawley asks Claude Code to build a fridge shopping list for the PaperMono device.
- The project reuses documented MonoMesh board support and adds list firmware, local storage and phone/server sync.
- The published design notes record repairs to keyboard, overlay and offline edit-queue failures.
Seamus Cawley used Claude Code to build a household shopping list for the M5Stack PaperMono, an ESP32-S3 device with an e-paper touchscreen. He says he did not hand-write the firmware and wanted to see whether the agent could make something useful for unfamiliar hardware. The reported result was in daily family use and on weekly shopping trips.
The published repository makes the work inspectable. It contains about 2,400 lines of C++, a FastAPI and SQLite server, a phone interface and hardware notes. Proven board and touch support came from MonoMesh; the sync client, local store, list screens and server were new. The project records debugging fixes for stale keyboard pointers during sync, overlays left on screen, blocked edit queues and pending additions disappearing after a fetch.
The useful pattern is a small physical product with a narrow interface, documented hardware reuse and a record of real failures. It also has clear limits. Wi-Fi credentials are compiled into the firmware, the server has no authentication, and only one PaperMono variant was tested. Battery claims need caution: the README describes light sleep, while the design notes say light sleep is absent and battery life has not been measured.
Prompt
Suggested prompt (written by Agents In Use, not the author's)
Source: Hacker News · Seamus Cawley / seamus_c
Frequently asked questions
What did the agent build?
PaperMono firmware plus a FastAPI and SQLite service and phone web interface for a shared shopping list.
Was all hardware support written from scratch?
No. The repository identifies board, touch, keyboard and display work adapted from MonoMesh.
Was battery life measured?
No. The design notes say battery life is unmeasured and disagree with the README about light sleep.
More details
Remaining steps
- Cawley reports daily household use and weekly shopping trips with the finished device.
About this account
Claude Code implemented the firmware and supporting application; the repository records hardware bring-up and several debugging iterations.
Firsthand account opened and read, with linked project documentation where available. Outcomes are author reports, not independently reproduced. Suggested prompt written by Agents In Use. README and design notes disagree on light sleep; do not infer battery runtime. One household and C153 device only.
Credit: Seamus Cawley / seamus_c
Source published 28 Sept 2026
Source checked 15 Oct 2026
Tools and topics
Claude Code · PaperMono · FastAPI · SQLite · PlatformIO
Claude Code · PaperMono · FastAPI
Editorial completeness: 100/100. Measures documented fields, not agent performance or verified outcomes.