🚀 Project Milestone: Automated HIL Integration

Frameworks: C++17, FreeRTOS, Pytest, GitHub Actions, Pre-commit

Objective: Establish a robust automated testing pipeline that verifies firmware logic on physical hardware before every commit and push.

🏗️ 1. Firmware Architecture Refactoring

To support automation, we moved away from hardcoded logic to a modular, command-driven architecture.

Table-Driven Command Dispatcher

We replaced a high-complexity if-else chain in appLogger::handleCommand with a Dispatch Table using modern C++ standards.

Pattern: Uses a CommandEntry struct to map string commands (e.g., dump_logs) to private member functions.

Logic: Utilizes std::find_if to search the table, reducing Cyclomatic Complexity from 13 down to 2.

Stack Safety: Implemented Segmented Printing in handlers (e.g., cmdGetTemp) to minimize stack usage by sending labels and values separately.

Task Registry (IRTOS Integration) Eliminated global task handles by implementing a Task Registry in the IRTOS interface.

Impact: appLogger now queries the RTOS for a list of registered tasks to report stack high-water marks without needing extern variables from main.cpp.

🐍 2. HIL Testing Framework (Python)

We built a pytest-based suite that communicates with the STM32 via UART to verify system state.

Hardware Discovery Logic (conftest.py)

To prevent the framework from crashing when the device is unplugged, we added “Hardware Discovery”.

Functionality: Checks for /dev/ttyACM0. If missing, it uses pytest.skip instead of failing, allowing CI/CD and pre-commit to proceed for non-hardware changes.

Test Scenarios (test_system.py)**

Stack Health: Verifies that all RTOS tasks (Heartbeat, SensorRead, etc.) are reporting valid stack margins.

Storage Integrity: Automates dangerous operations like bulk_erase and event_sector_erase, verifying erase counts and data persistence.

Sensor Accuracy: Uses regex to validate that temperature and humidity readings follow the correct numeric format.

🛠️ 3. Local Automation & VS Code Integration

Integrated the HIL suite into daily coding workflow for “one-click” verification.

VS Code Tasks (tasks.json)

Added a dedicated task to run HIL tests and generate a self-contained HTML report.

Output: Generates hil_report.html for instant visual feedback on hardware status.

Local Guardrails (.pre-commit-config.yaml) Implemented a pre-commit hook that triggers HIL tests before every git commit.

Optimization: Used file filters (files: ^04_FreeRTOS_Cpp/(App/|HIL_test/)) to ensure HIL tests only run when firmware or test scripts are modified.

Environment: Configured the hook to use .venv/bin/pytest to ensure library consistency.

☁️ 4. Remote DevOps (GitHub Actions)

The Pipeline (ci_quality.yml)

Job 1: Quality Gate (Cloud): Runs cppcheck, lizard, and unit tests on GitHub’s servers.

Job 2: HIL Testing (Local PC):

  • Build: Cross-compiles the C++ source into a .bin file.
  • Flash: Physically writes the new firmware to the DISCO board via st-flash.
  • Verify: Executes the pytest HIL suite on the fresh firmware.
  • Upload: Sends the hil_report.html back to GitHub as a build artifact.

Isolation Fix:

Solved the externally-managed-environment error (PEP 668) by forcing the runner to use the local .venv for all pip operations.

Permissioning:

Ensured the runner user has dialout group access to interact with the USB serial port.

🪵 5. The “Hustle” Log (Key Bug Fixes)

During this development phase, we identified and resolved several critical “gotchas”:

Issue Root cause Resolution
Silent xtoa Failure Buffer size passed as 6. Used sizeof(buf) to ensure app_ftoa safety checks pass.
Race Condition Prompt > sent before Logger Task finished. Switched operation completion messages to synchronous sendCommandResponse.
HIL False Positive Search string TS: mismatch. Synchronized Python assert strings with actual C++ output labels.
Bitwise Storage Float logging confusion. Clarified memcpy bit-preservation for storing floats in uint32_t arrays.
CI Failures Missing symlinks for .venv/bin/pytest. Added symlink “magic tricks” in the GitHub Action quality-gate job.

Useful Commands for Maintenance

Restart Runner: cd ~/actions-runner && ./run.sh

Manual HIL Run: pytest 04_FreeRTOS_Cpp/HIL_test/test_system.py --html=report.html

Check USB Permissions: sudo usermod -a -G dialout $USER

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