lab-rv32i-freertos-integration/doc/card-plan.md

K16 — Integrated real-time application and evidence report

Position

• Series: FreeRTOS C++
• Lesson: L15, card K16
• Duration: 30 minutes
• Final integration card; no new wrapper primitive
• Reproducible end-to-end evidence on Hazard3

Outcome

The student composes ownership, storage, task priorities, startup coordination, ISR/timer boundaries, queue pressure and memory/stack diagnostics into one defensible real-time service graph.

Lesson plan

Time	Mode	Evidence
0–5	inventory	static services delta 0; dynamic report queue 128 B
5–10	startup	EventGroup barrier=0x7; task priorities and ownership
10–15	inputs	real IRQ tick 1; timer ticks 5/10
15–20	pipeline	three samples, transform sum 120
20–25	pressure	peaks 2/2, sequence 4 dropped, end marker recovers
25–30	report	latency 6, stack HWM, 24-event digest c474ac09

Acceptance

• no new wrapper primitive is introduced;
• producer, processor and reporter are StaticTask instances;
• startup EventGroup remains at mask 0x7;
• external IRQ wakes producer at tick 1 and requests exactly one yield;
• periodic timer callbacks occur at ticks 5 and 10, then timer becomes inactive;
• three samples are produced, processed and reported with sum 120;
• input and report queues both reach depth 2;
• sequence 4 is explicitly drop-newest and the end marker later succeeds;
• static services have heap delta zero;
• exactly one persistent dynamic Queue costs 128 B;
• oversized fallible allocation returns null without changing free heap;
• producer/processor/reporter stack HWM are positive and recorded;
• end-to-end latency is 6 ticks and trace digest is c474ac09;
• target exits with PASS.

Main traps

1. Adding abstraction without a new invariant.
2. Hiding an unbounded allocation or queue wait in the periodic path.
3. Treating a pressure drop as success or failing to count it.
4. Performing transformation in ISR/timer callback instead of a task.
5. Reporting screenshots without source, timestamped trace and repeatable gate.