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System Design/Engineering Review Report.md

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+# Engineering Review Report
+
+## A. Executive Summary
+
+### Overall System Maturity Level
+The ASF Sensor Hub demonstrates a well-structured architecture with clear layering, defined responsibilities, and adherence to embedded system constraints. However, several critical gaps and risks need to be addressed before proceeding to the implementation phase.
+
+### Major Risks (Top 5)
+1. **Cross-Feature Conflicts**: Potential timing conflicts between OTA updates and DAQ operations.
+2. **State Machine Completeness**: Undefined transitions for error handling and degraded states.
+3. **Data Integrity Risks**: Insufficient guarantees for data persistence during power loss.
+4. **Security Gaps**: Lack of detailed secure boot and cryptographic key management mechanisms.
+5. **Scalability Concerns**: Limited provisions for adding new sensor types or features.
+
+### Go / No-Go Recommendation
+**No-Go**: Address the identified critical risks and gaps before proceeding to the implementation phase.
+
+---
+
+## B. Detailed Findings
+
+### 1. Architecture
+
+#### Findings:
+- **Layering & Separation of Concerns**: Proper abstraction boundaries are defined, but direct hardware access by features bypassing the System Manager is a risk. **Severity: Major**
+- **State Machine Validity**: Some states (e.g., ERROR, DEGRADED) lack defined transitions and behaviors. **Severity: Critical**
+
+#### Recommendations:
+- Enforce strict access controls to hardware and persistence layers.
+- Define and document all state transitions and behaviors.
+
+### 2. Requirements
+
+#### Findings:
+- **Missing Requirements**: No explicit requirements for handling SD card wear or power loss scenarios. **Severity: Critical**
+- **Conflicting Requirements**: OTA updates may interfere with real-time DAQ operations. **Severity: Major**
+
+#### Recommendations:
+- Add requirements for wear leveling and power loss recovery.
+- Define OTA timing constraints to avoid conflicts.
+
+### 3. Performance
+
+#### Findings:
+- **Memory Usage Risks**: High-frequency sampling and local filtering may exceed ESP32-S3 memory limits. **Severity: Major**
+
+#### Recommendations:
+- Optimize memory usage by profiling and limiting buffer sizes.
+
+### 4. Reliability
+
+#### Findings:
+- **Fault Tolerance**: No defined behavior for sensor failures during runtime. **Severity: Major**
+
+#### Recommendations:
+- Implement fallback mechanisms for failed sensors.
+
+### 5. Security
+
+#### Findings:
+- **Secure Boot**: No detailed mechanism for secure boot and firmware authenticity verification. **Severity: Critical**
+
+#### Recommendations:
+- Implement secure boot and cryptographic verification for firmware.
+
+### 6. Maintainability
+
+#### Findings:
+- **Scalability**: Adding new sensors requires significant manual effort. **Severity: Minor**
+
+#### Recommendations:
+- Use a modular approach for sensor integration.
+
+---
+
+## C. Missing / Risky Areas
+
+### Missing System Requirements
+- SD card wear leveling.
+- Power loss recovery mechanisms.
+
+### Missing System States
+- Detailed ERROR and DEGRADED state transitions.
+
+### Missing Failure Handling
+- Sensor failure fallback mechanisms.
+
+### Missing Documentation
+- Secure boot and cryptographic key management.
+
+---
+
+## D. Improvement Recommendations
+
+1. **Architectural Enhancements**:
+   - Enforce strict abstraction boundaries.
+   - Define all state transitions and behaviors.
+
+2. **Requirement Additions**:
+   - Add requirements for SD card wear leveling and power loss recovery.
+
+3. **Security Improvements**:
+   - Implement secure boot and cryptographic verification mechanisms.
+
+4. **Scalability Enhancements**:
+   - Adopt a modular approach for sensor integration.
+
+---
+
+## E. Generated Artifacts
+
+### State Machine Diagram
+```mermaid
+graph TD
+    INIT --> IDLE
+    IDLE --> RUNNING
+    RUNNING --> DEGRADED
+    RUNNING --> ERROR
+    DEGRADED --> TEARDOWN
+    ERROR --> TEARDOWN
+    TEARDOWN --> INIT
+```
+
+### Cross-Feature Conflict Table
+| Feature A       | Feature B       | Conflict Description          | Resolution Recommendation       |
+|-----------------|-----------------|-------------------------------|----------------------------------|
+| OTA             | DAQ            | Timing conflicts              | Define OTA timing constraints   |
+| Persistence     | Power Loss     | Data corruption risks         | Add wear leveling and recovery  |
+
+---