Gabriel Kaszewski
6ad76b98a2
CONTEXT.md: domain model with entities (WidgetConfig, DataSource, LayoutPreset), value objects (Layout, LayoutNode, KeyMapping, WidgetState, Sizing), architecture decisions (CQRS, static dispatch, postcard), client domain model, and design constraints.
1.1 KiB
1.1 KiB
0003 — postcard over FlatBuffers
Status: accepted Date: 2026-06-18
Context
Need a binary serialization format for the TCP protocol between server and ESP32 clients. Must be compact (bandwidth-constrained), ideally no_std compatible for future bare-metal targets.
Decision
Use postcard with serde derives instead of FlatBuffers.
Alternatives considered
FlatBuffers — zero-copy reads, schema-driven. But requires external codegen toolchain (flatc), no_std support is limited, and zero-copy is overkill for our small messages (a handful of widgets).
Custom binary protocol — maximum control, zero deps. But significant implementation effort for serialize/deserialize code, error-prone, and postcard already solves this.
Consequences
no_stdprotocol crate out of the box — future-proof for bare-metal targets.- No codegen step — types are normal Rust structs with serde derives.
- Compact wire format via varint encoding.
- No zero-copy reads — messages are deserialized into owned types. Acceptable for our message sizes.
- Adds
serdeandpostcardas dependencies to the protocol crate.