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PicoWAL

Micro-database appliance. Runs on a $6 microcontroller.

⌥ repo

A networked micro-database running on a Raspberry Pi Pico 2W with a 3.5" touchscreen and 16GB SD card. Full SSR web UI, user auth, schema management, a query language with joins and aggregates, batch writes, and OTA firmware updates.

Architecture

  • RP2350 Cortex-M33, 520KB SRAM
  • Binary schema cards — packs (tables) containing cards (rows)
  • Pack 0-1 in 4MB flash (system data), Pack 2+ on SD (user data)
  • Query engine: S:fields F:packs W:conditions with joins
  • LCD dashboard showing SSID, IP, flash/SD usage

Data model

Data is organised into packs (like tables) containing cards (like rows). Each card is a binary blob with a 4-byte magic header followed by ordinal-tagged fields. No ORM. No query planner committee meetings. Just structured bytes on an SD card.

A database is just a transformation engine over byte streams.

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