49 lines
2.0 KiB
Markdown
49 lines
2.0 KiB
Markdown
 
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# CLAUDE.md
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ESPHome external component for a Samsung 2×20 serial VFD (5 V TTL, 9600 8N1,
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write-only). It is consumed from git by an ESPHome server through
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`external_components: source: github://...`, so the layout must stay
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`components/samsung_vfd/` at the repo root.
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## Layout
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- `components/samsung_vfd/__init__.py`: config schema, codegen and the action
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registrations (`print`, `printf`, `clear`, `home`).
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- `components/samsung_vfd/samsung_vfd.h`: the class, the control-byte constants
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and the templated action classes.
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- `components/samsung_vfd/samsung_vfd.cpp`: the shadow buffer, word wrap,
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UTF-8 → single-byte sanitising and `flush_()`.
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- `examples/samsung-vfd.yaml`: the full reference device config. It pulls the
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component from GitHub; for local work, switch to the commented
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`type: local, path: ../components` source.
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## Design rules
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- `lines_` is the screen as it should be, each line padded to exactly `cols_`.
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Every change goes through `flush_()`. It rebuilds the payload, returns early
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if the payload equals `last_payload_`, and otherwise sends `0B` (home) plus
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the payload. Don't clear before redrawing: that causes flicker.
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- Anything that changes the display out of band (clear, init) must reset
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`last_payload_` so the next flush retransmits.
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- Text sent to the display is one byte per character; always pass it through
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`sanitize_()`.
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- Keep the protocol constants in `samsung_vfd.h`. Only `ESC @`, `0C` and `0B`
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are known to work.
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## Checking changes
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Hardware isn't available to Claude, so validate with ESPHome itself:
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```
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pip install esphome
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cd examples
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# switch external_components to the local source first
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esphome config samsung-vfd.yaml # schema check
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esphome compile samsung-vfd.yaml # full C++ build
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```
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`secrets.yaml` is gitignored. Copy `examples/secrets.yaml.example` to
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`examples/secrets.yaml` to compile.
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Follow ESPHome C++ style: `this->` on members, a trailing `_` on protected
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members, and the `esphome::samsung_vfd` namespace.
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