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 ==== 8.1 Achievements ====
-The Connect project set out to transform a standard metro carriage into a participatory space that counteracts digital isolation through ambient light interaction and asynchronous voice exchange. Evaluated against the four objectives defined in Section 1.4, all primary targets were met.
+The CONNECT and share project successfully demonstrated the feasibility of transforming a standard metro carriage into a participatory space, counteracting digital isolation through ambient light interaction and asynchronous text messaging. Evaluated against the core objectives defined in Section 1.4, the primary functional milestones were achieved within the scope of the development environment.
-The functional core of the system was fully validated. The two-node prototype demonstrates pressure detection via Velostat sensors, bidirectional CAN bus communication between an ESP32-C3 sensor node and a central node, and real-time RGB LED feedback driven by the WS2813 addressable strip. ADC output responded linearly to applied pressure, the CAN bus achieved a Packet Delivery Ratio exceeding 99.9 %, and LED output was confirmed free of dead pixels and flickering across the full animation cycle. The potentiometer-based sensitivity calibration allowed reliable threshold adjustment independent of firmware changes. The interrupt-driven, deep-sleep firmware architecture performed correctly on both nodes and scales to additional nodes without modification.
+The technical core of the distributed network was validated. The implemented two-node benchtop prototype proved the viability of pressure detection via custom air-gap Velostat sensors, bidirectional CAN bus communication between standard ESP32 nodes, and real-time RGB LED feedback via a 1-meter Seeed WS2813 strip. The ADC infrastructure mapped the compression curves reliably, and the CAN network achieved a 100% packet delivery ratio under laboratory conditions. Although the physical calibration potentiometer was bypassed for a optimized fixed resistor in the final bench layout, the stateless, interrupt-driven firmware architecture was fully validated, demonstrating correct deep-sleep transitions and the capacity to scale to an 11-node network without firmware modifications.
-All performance targets were met. End-to-end latency from sensor contact to LED illumination was confirmed below 100 ms. No ghost triggers were observed during electromagnetic interference testing with a brushed DC motor operating in proximity to the CAN wiring. Enclosure surface temperature remained below 50 °C after four hours of continuous operation at 80 % LED brightness, end-of-line voltage remained above 4.7 V under full white load, and the system retained full electrical sensitivity after 1000 automated trigger cycles.
+Key performance and structural metrics were successfully satisfied. End-to-end latency from initial touch to LED response was verified below the 100 ms threshold. While high-voltage rails were omitted from the bench setup, the continuous 5V loop maintained an end-of-line voltage above 4.7V under full load, with the enclosure surface temperature remaining safely below 50 °C. Structural safety was verified through Finite Element Analysis (FEA) within SimScale, confirming that peak Von Mises stresses under a 100 N force vector remain securely below the elastic yield threshold of the polymer.
-Structural and safety validation was completed. Finite Element Analysis of both the ceiling-mounted main box and the pole-mounted secondary node confirmed safety factors exceeding 12.0 and 30.0 respectively against the yield strength of Nanovia PA Rail. Electrical continuity between enclosure and ground was confirmed below 0.1 Ω, all cable and filament materials carry V-0 or LSHF certification, the sensor assembly survived a 5 kg impact test without loss of function, and no moisture ingress was detected following cleaning mist exposure.
+Software testing passed in full validation. CAD integration models confirmed zero mechanical interference between components while maintaining the target 5 mm clearance. In software simulations, the CAN arbitration logic correctly prioritized critical node IDs during forced frame collisions, and the animation algorithms ran continuously for 24 hours without memory leaks or buffer overflows. Additionally, the heartbeat timeout detection logic triggered within 500 ms of a simulated CAN failure, successfully switching the LED output to a static safety white state.
-Software testing passed in full. CAD integration confirmed zero mechanical interference between components with the required 5 mm clearance maintained. CAN bus arbitration correctly prioritised the higher-priority node ID under forced collision conditions. The animation algorithm ran for 24 hours in simulation without memory leaks or buffer overflows. Heartbeat timeout detection triggered within 500 ms of CAN disconnection and correctly switched the LED output to static safety white.
+The web platform reached a fully deployable state. The Supabase database and Next.js backend demonstrated high scalability during load testing, sustaining 1000 concurrent requests with a zero error rate and a mean write latency of 195.77 ms. All five Jest unit test cases covering the API routes passed successfully in 0.277 seconds.
-The web platform reached a deployable state. Load testing at 1000 concurrent requests produced a zero error rate and a mean latency of 195.77 ms on the write endpoint. The System Usability Scale evaluation returned a mean score of 86.59 across 11 participants, placing the interface in the "Excellent" range, well above the industry average of 68. All five Jest unit test cases covering the GET and POST API routes passed in 0.277 seconds. User acceptance testing confirmed that more than 80 % of non-technical participants identified the pole sensor as the interaction point within 5 seconds, no participants reported glare or eye strain at maximum brightness, users correctly associated the light animations with system state, and the interaction was successfully triggered by participants across the full range of tested heights and hand strengths.
+The System Usability Scale (SUS) evaluation yielded an "Excellent" mean score of 86.59 across 11 participants, proving the interface is highly intuitive. User acceptance testing (UAT) confirmed that non-technical participants successfully identified the interaction zones without instructions, reported no glare or eye strain under the diffuser profile, correctly associated the light animations with the system states, and successfully triggered the interaction across a wide range of tested heights and hand strengths.
-The prototype was delivered within the 100 € budget constraint at a total cost of 97.92 €.
+The complete physical prototype was delivered within the 100 EUR budget constraint at a total cost of 97.92 EUR.
 ==== 8.2 Limitations ====
-The prototype represents a deliberate functional reduction and several gaps between the designed solution and the implemented system remain relevant for future iterations.
+As a deliberate functional reduction for laboratory validation, several gaps remain between the ideal designed solution and the implemented prototype:
-The prototype covers a single handrail segment with two nodes. The full designed solution requires eleven sensor nodes distributed across a carriage. The two-node configuration validates the communication protocol and interaction loop but does not exercise bus arbitration under simultaneous multi-node transmission at full network scale.
+  * **Network Scale:** The prototype was restricted to a two-node configuration on a single handrail segment. While this validated the protocol loop, it did not fully exercise bus arbitration under simultaneous multi-node transmissions at a full 11-node carriage scale.
+  * **Signal Mismatch and Artifacts:** The visual feedback subsystem suffered from high-frequency flickering during idle states. This was isolated to a logic-level mismatch, as the ESP32 GPIO operates at 3.3V CMOS, while the Seeed WS2813 LED strip requires a minimum input high threshold (VIH) of 3.5V when powered at 5.0V.
-Fire-rated enclosures were not fabricated for the prototype. The housings are 3D-printed in PLA, which does not meet EN 45545-2 flammability requirements. The PA Rail enclosures specified for deployment were impractical to source within the prototype budget. Physical compliance testing of the enclosure material against railway fire safety standards therefore remains pending.
+  * **Material and Fire Safety Compliance:** Due to budget restrictions, fire-rated Nanovia PA Rail enclosures, LSHF cabling, and specific railway testing (such as continuity tests, 5 kg impact tests, and cleaning mist exposure) could not be physically executed. The prototype relied on standard 3D-printed PLA, meaning compliance against the EN 45545-2 railway flammability matrix remains pending.
+  * **Power Architecture Simplification:** The dual-rail (12V + 5V) distribution network and its six decentralized step-down switching converters were replaced by a single 5V bench supply. The empirical behavior of the power network under worst-case current draws across all eleven nodes remains unverified.
-The dual-rail power architecture was not implemented. The prototype uses a single 5 V bench supply in place of the six step-down converters and dual 12 V and 5 V distribution chain specified for the full installation. Behaviour of the power architecture under worst-case current draw across all eleven nodes has not been empirically verified.
+  * **Real-World Behavior Testing:** Phase 2 (the text platform) was evaluated via isolated load tests and usability surveys, but end-to-end passenger behaviors—such as QR code discovery at exit doors and the intentional interaction delays—were not observed within a realistic transit environment.
-Phase 2 was not evaluated in a simulated transit environment. The QR voice messaging platform was assessed via load testing and SUS scoring, but end-to-end passenger behaviour, including QR code discovery at exit doors and the intentional delay mechanic, was not observed under realistic boarding and alighting conditions.
 ==== 8.3 Future Development ====
-Scaling from two nodes to the full eleven-node network is the primary technical extension. This requires fabrication of additional Sensor Node PCBs and validation of bus arbitration timing under simultaneous transmission from multiple nodes. The heartbeat timeout and safety-white fallback logic should also be confirmed correct when any single node drops from a live eleven-node network.
+Future iterations must focus on transitioning the validated benchtop architecture into a rail-compliant deployment:
-Enclosure fabrication in Nanovia PA Rail is required before any deployment in a transit environment. A Portuguese or EU-based supplier should be identified to reduce logistics cost and lead time at scale. The enclosure geometry is defined and FEA-validated; procurement and physical fire compliance testing are the remaining steps.
-The dual power rail should be implemented and verified with converters sized for worst-case current draw across the full node count. Voltage drop along the LED strip should be re-confirmed against the 4.7 V minimum under the full three-strip, eleven-node load.
-For Phase 2, a pilot deployment in a controlled transit-adjacent environment, such as a station concourse or a simulated carriage mockup, would allow end-to-end validation of the QR discovery flow, the intentional delay mechanic, and the content moderation pipeline under realistic passenger behaviour. A longitudinal dataset from Phase 2 submissions would also provide quantitative grounding for the social impact claims established in Sections 2.3.1 and 5.5.
-The heart rate sensing capability referenced in Section 1.5.3 and the auditory feedback output described in Section 1.4 were not implemented in this iteration. Both represent additional sensing and output channels that would enrich the interaction model and bring the system closer to the full vision outlined in the initial objectives.
+  * **Hardware Sizing and Signal Optimization:** Incorporating a dedicated hardware logic-level shifter (such as the 74HCT125) is required to step the ESP32 data lines up to 5.0V, permanently eliminating LED flickering. Additionally, physical 10 kΩ calibration potentiometers should be populated onto custom Sensor Node PCBs to enable manual threshold adjustments.
+  * **Full Network and Power Scaling:** Fabricating the full 11-node network is necessary to stress-test simultaneous CAN bus collisions. This must be paired with the implementation of the designed dual-rail power architecture to verify voltage drop stability along the full multi-strip framework under full white load.
+  * **Regulatory Manufacturing:** Future enclosures must be fabricated using Nanovia PA Rail or equivalent EN 45545-2 certified polymers. Physical testing for electrical continuity (below 0.1 Ohm), impact resistance, and ingress protection (IP) must be conducted using these production-grade materials.
+  * **Transit Pilot and Social Impact:** Deploying the prototype or the recycled cork "Social Hub" packaging modules within a controlled transit mockup or station concourse will allow for the validation of passenger flows, QR discovery mechanics, and content moderation pipelines under realistic conditions. Collecting a longitudinal dataset from these interactions will provide quantitative grounding for the project's long-term social impact claims.
+  * **Sensor Integration:** Future iterations should implement the biometric heart-rate sensing arrays and auditory feedback channels outlined in the original scope to enrich the inclusive interaction model.