Device sync

stella-x4 is a standalone spaced-repetition firmware for the Xteink X4 e-ink reader. It runs the same SM2 review loop offline, from the SD card, and syncs with a Stella server over WiFi.

Connecting a device#

1. Create a token in /settings/tokens.
2. Give the device your Stella URL and that token (see the stella-x4 README for how).

The device then syncs in explicit sessions. Each session uploads the reviews done on the device, downloads any decks that changed on the server, and exchanges scheduling state in both directions (the most recent change wins).

What syncs#

• Server decks show up on the device as read-only mirrors. Editing, deleting, and choosing which decks to study happen on the server.
• Reviews done on the device land in the server’s review history, and are safe to upload more than once.
• Cards reach the device as plain text: the card formatting is stripped, furigana becomes base（reading）.

The sync API lives under /api/x4 and only accepts bearer tokens.