[YashAnand69]

Interrupting HC-SR04 distance measurement with Ctrl+C during its acquisition wait leaves the recurring trigger pulses enabled. The command that returns the trigger output LOW is skipped when the wait raises.

Put the existing wait in try/finally so the LOW command is attempted before propagating the interruption. Successful capture timing, pulse settings, command order and distance calculation remain unchanged. The logic analyzer is not stopped or reconfigured by this change.

Validation: four interruption regressions fail on unchanged main; four normal/error controls pass. The fixed branch passes eight new tests plus 33 existing hardware-independent CLI, Pico and gas-sensor tests (41 total). Tests construct HCSR04 with controlled instrument interfaces, verify SQ1/SQ4 cleanup, retain the original exception and check successful distance calculation. Configured Black, Flake8, Bandit and pydocstyle, wheel/sdist and Sphinx builds pass; seven existing documentation warnings remain.

No physical PSLab/HC-SR04 or full hardware integration run was performed. Cleanup still requires a working device transport; it cannot guarantee the output changes if the LOW command itself fails. Current rules, issue claims and all open PR patches were checked; no overlapping cleanup fix found. Developed and tested with Codex assistance.

Summary by Sourcery

Guarantee that HC-SR04 measurement interruptions disable the trigger output before propagating the error.

Bug Fixes:

• Ensure ultrasonic sensor trigger outputs are stopped when measurement acquisition is interrupted, while preserving the original exception.
• Preserve trigger cleanup across capture timeout and invalid echo errors.

Tests:

• Add hardware-independent regression coverage for interrupted waits, successful measurements, trigger-channel variants, and capture errors.

Summary by CodeRabbit

• Bug Fixes
  • The ultrasonic distance sensor now resets its trigger after a measurement, including when the measurement is interrupted or encounters an error. This helps prevent the trigger from being left active after an unsuccessful reading.

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Reviewer's Guide

The PR makes HC-SR04 measurement cleanup exception-safe by placing the existing wait in a try/finally that drives the trigger LOW, and adds controlled-interface tests covering interrupted waits, both trigger pins, command ordering, and existing success/error outcomes.

Sequence diagram for exception-safe HC-SR04 measurement cleanup

sequenceDiagram
    participant Caller
    participant HCSR04
    participant PWM
    participant Timer
    participant LogicAnalyzer

    Caller->>HCSR04: estimate_distance(average)
    HCSR04->>PWM: set_state(trigger HIGH, duty_cycles)
    HCSR04->>Timer: sleep(measure_period * (average + 1))
    alt wait completes
        Timer-->>HCSR04: return
    else wait interrupted
        Timer-->>HCSR04: raise interruption
    end
    HCSR04->>PWM: set_state(trigger LOW)
    alt wait was interrupted
        HCSR04-->>Caller: propagate original interruption
    else wait completed
        HCSR04->>LogicAnalyzer: fetch_data()
        HCSR04-->>Caller: return distance
    end

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File-Level Changes

Change	Details	Files
Guarantee trigger-output cleanup when acquisition waiting is interrupted while preserving normal measurement behavior.	Wrap the post-capture wait in try/finally. Attempt to drive the configured trigger pin LOW before propagating the original exception. Leave capture, timing, pulse generation, fetch, and distance-calculation flow unchanged.	pslab/external/hcsr04.py
Add hardware-independent regression coverage for interruption cleanup and unchanged successful/error behavior.	Test KeyboardInterrupt and RuntimeError cleanup for SQ1 and SQ4 while preserving exception identity and skipping fetch. Verify successful command order, pulse parameters, timing, cleanup, and distance calculation. Verify timeout and high-echo errors still occur after the trigger is stopped.	tests/test_hcsr04_cleanup.py

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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

• Configuration used: defaults
• Review profile: CHILL
• Plan: Advanced
• Run ID: 3a547c83-97cf-41f5-8bad-b3aea7e4a6be

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📥 Commits

Reviewing files that changed from the base of the PR and between 08de0d0 and 2dfd4e3.

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📒 Files selected for processing (2)

• pslab/external/hcsr04.py
• tests/test_hcsr04_cleanup.py

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Included review availability: This review used your included allowance. Your plan provides up to 4 included reviews per hour; 3 remain after this review.

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📝 Walkthrough

Walkthrough

estimate_distance now resets the trigger pin in a finally block. Tests check trigger cleanup when waiting raises, when capture data times out, when the initial echo state is high, and after a successful measurement.

Changes

HCSR04 trigger cleanup

Layer / File(s)	Summary
Trigger reset and measurement tests pslab/external/hcsr04.py, tests/test_hcsr04_cleanup.py	estimate_distance resets the trigger pin in a finally block. Mock-based tests cover wait exceptions, successful measurements, timeouts, and a high initial echo state.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix

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Merge Risk | ⚪ Minimal · up to 2dfd4

Merge Risk: ⚪ Minimal · up to 2dfd4

This change makes the HC-SR04 trigger output get stopped when a measurement is interrupted, and normal measurements behave as before. It was not tested on physical hardware, but no concrete merge-blocking risk remains.

Security Architecture Review

Security architecture risk: 🔵 Low · up to 2dfd4

The change improves interruption cleanup without expanding access to the device. Remaining uncertainty concerns failed cleanup commands and overlapping use of the same hardware; stopping the output is not guaranteed in those conditions.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

• inferred — The direct changed outcome is a LOW command for the configured trigger on the existing PSLab connection after an interrupted wait. Any interference with another operation sharing that hardware remains within the existing shared-device control scope; supported concurrent sharing is not established.

Trust Boundaries and Controls

• observed — The device-transport boundary remains unchanged. Cleanup uses the same device command and acknowledgement sequence that previously ran after successful waits, rather than acquiring additional privileges or selecting a new destination.

Resilience and Maintainability Implications

• inferred — Finally improves containment of interrupted waits but provides an attempted stop, not an unconditional hardware-state guarantee. The unchanged set_state implementation updates local channel state before transmitting the command, so a transport failure can leave local state inconsistent with hardware. That failure mode predates this PR, although cleanup is now attempted on additional exception paths.

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Pre-merge checks | 4 | 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 40.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 5 functions across 2 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly and concisely describes the main change: stopping ultrasonic trigger pulses when measurement is interrupted.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

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