Non Blocking Patterns

Non-Blocking Patterns

Keep the main loop responsive and make timing behavior testable. Prefer C/C++ patterns that can be compiled for the exact board; use Python only for relevant test or log analysis tooling.

Intake

Record board/core version, task periods, deadlines, maximum work duration, input bounce, serial/network behavior, watchdog policy, interrupt constraints, and the safety response for missed deadlines.

Process

1. List each periodic or event-driven task with period, deadline, and worst-case work. Identify any blocking library call.
2. Replace long delay() calls with unsigned wrap-safe elapsed checks such as if (static_cast<unsigned long>(now - last) >= period). Use hardware timers or RTOS tasks only when board and framework support is confirmed.
3. Model multi-step work as an explicit state machine with bounded transitions; do not hide waits inside a helper.
4. Debounce inputs using a stable-state timer or event filter, not a blocking pause. Bound serial parsing, network retries, and sensor conversion waits.
5. Define watchdog feeding, output inhibit, timeout, and recovery behavior.
6. Measure loop latency and task jitter under representative logging, radio, storage, and actuator load.

Anti-rationalization

Verification

• No unbounded blocking call remains in the time-critical path without a documented reason and timeout.
• Debounce, wraparound, timeout, and missed-deadline cases have tests.
• Exact-target compile proof and timing/serial evidence are separate.
• Outputs enter a safe state when a task, sensor, or communication path times out.

Shared output contract

Use the shared Arduino skill contract: state assumptions, required tools and versions, implementation steps, tests/evidence by proof stage, known limitations, and recovery/security notes.