Project Orientation

Library targets embedded-hal 1.0 in no_std environments; keep APIs allocator-free and resilient to HAL timing quirks.
Supported controllers/adapters: HD44780 variants (PCF8574T, Adafruit MCP23008, dual-controller), AiP31068, and ST7032i. Each has dedicated hardware and action layers—reuse those abstractions instead of bypassing them.
Error paths must use CharacterDisplayError; extend the enum only when the behaviour is externally observable.

Development Workflow

Touch both the high-level facade in src/lib.rs and the appropriate driver module when introducing a new capability.
Maintain compatibility with optional features (defmt, ufmt). Ensure new code compiles when these features are disabled.
Respect existing timing expectations; use the provided delays rather than busy waits or sleeping loops.

Unit tests are mandatory for every behavioural change. Extend the existing embedded-hal-mock based tests to cover new I²C transactions, timing assumptions, and failure paths.
When fixing a bug, first reproduce it with a failing unit test, then implement the fix. Do not remove tests without a replacement.
Run cargo test in the root crate before handing off any change set. If tests cannot run in your environment, explain why and supply the commands you attempted.

Rust 2021 edition, #![no_std] defaults; avoid introducing std dependencies outside guarded test modules.
Keep files ASCII unless you have a strong reason otherwise. Use descriptive method names and prefer small, composable helper functions.
Document non-obvious hardware interactions with short comments; do not duplicate datasheet prose.

All new logic has unit-test coverage.
cargo fmt, cargo clippy --no-deps, and cargo test succeed (note any exceptions).
Public API changes are documented in doc comments and, if user-visible, in CHANGELOG.md.
Verify no accidental regressions in multi-controller addressing or buffer bounds.