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52 lines
2.0 KiB
Markdown
52 lines
2.0 KiB
Markdown
# K16 — Integrated real-time application and evidence report
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## Position
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- Series: FreeRTOS C++
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- Lesson: L15, card K16
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- Duration: 30 minutes
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- Final integration card; no new wrapper primitive
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- Reproducible end-to-end evidence on Hazard3
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## Outcome
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The student composes ownership, storage, task priorities, startup coordination,
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ISR/timer boundaries, queue pressure and memory/stack diagnostics into one
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defensible real-time service graph.
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## Lesson plan
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| Time | Mode | Evidence |
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| --- | --- | --- |
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| 0–5 | inventory | static services delta 0; dynamic report queue 128 B |
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| 5–10 | startup | EventGroup barrier=0x7; task priorities and ownership |
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| 10–15 | inputs | real IRQ tick 1; timer ticks 5/10 |
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| 15–20 | pipeline | three samples, transform sum 120 |
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| 20–25 | pressure | peaks 2/2, sequence 4 dropped, end marker recovers |
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| 25–30 | report | latency 6, stack HWM, 24-event digest c474ac09 |
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## Acceptance
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- no new wrapper primitive is introduced;
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- producer, processor and reporter are StaticTask instances;
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- startup EventGroup remains at mask 0x7;
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- external IRQ wakes producer at tick 1 and requests exactly one yield;
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- periodic timer callbacks occur at ticks 5 and 10, then timer becomes inactive;
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- three samples are produced, processed and reported with sum 120;
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- input and report queues both reach depth 2;
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- sequence 4 is explicitly drop-newest and the end marker later succeeds;
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- static services have heap delta zero;
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- exactly one persistent dynamic Queue costs 128 B;
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- oversized fallible allocation returns null without changing free heap;
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- producer/processor/reporter stack HWM are positive and recorded;
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- end-to-end latency is 6 ticks and trace digest is c474ac09;
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- target exits with PASS.
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## Main traps
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1. Adding abstraction without a new invariant.
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2. Hiding an unbounded allocation or queue wait in the periodic path.
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3. Treating a pressure drop as success or failing to count it.
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4. Performing transformation in ISR/timer callback instead of a task.
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5. Reporting screenshots without source, timestamped trace and repeatable gate.
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