PART3 - Edge Environmental Sentinel

This Implementation Document for the Edge Environmental Sentinel (EES) is basically a how-to guide, drawn from the project's technical specifications and functional design. It lays out the physical hookups, the main firmware structure, and the testing steps needed to get the system up and running on the NXP FRDM platform.

1. Hardware Interconnections

The EES uses a Hub-and-Spoke architecture. The Central Hub manages global logic, while distributed Edge Nodes handle localized sensing.

2. Firmware Implementation & Coding Examples

The software is developed in the NXP MCUXpresso IDE using the MCUXpresso SDK.

A. Edge Node: Data Packet Structure (C)

To minimize overhead, data is transmitted as a raw byte structure rather than JSON.

C
typedef struct {
uint8_t nodeId;      // Unique Zone ID
float temperature;   // LPADC Reading
float lightLevel;    // Ambient Light (Lux)
uint8_t status;      // 0 = Normal, 1 = ALERT
} SensorPacket;

void SendToHub(SensorPacket *packet) {
// Send raw structure bytes over UART
UART_WriteBlocking(LPUART0, (uint8_t *)packet, sizeof(SensorPacket));
}

B. Central Hub: Adaptive Threshold Logic (C)

The Hub parses incoming packets and triggers GPIO-linked relays based on environmental thresholds.

C
void ProcessNodeData(uint8_t *buffer) {
SensorPacket *p = (SensorPacket *)buffer;
// Check for high-temperature threshold (>30C)
if (p->temperature > 30.0f || p->status == 1) {
GPIO_PinWrite(BOARD_RELAY_GPIO, BOARD_RELAY_PIN, 1U); // Activate Cooling
UpdateVisualAlert(RED); // Set Hub RGB LED to Alert state
} else {
GPIO_PinWrite(BOARD_RELAY_GPIO, BOARD_RELAY_PIN, 0U); // Normal Operations
UpdateVisualAlert(GREEN);
}
}

3. Test Procedures for Qualification

A four-tier validation framework is used to qualify the implementation results.

Unit Qualification (Sensor Accuracy): * Procedure: Compare Edge Node LPADC temperature readings against a calibrated reference thermometer. *Pass Criteria: Accuracy within +/- 0.5°C tolerance.

Communication Integrity (UART Stress Test): *Procedure: Flood the UART line with high-frequency packets and monitor for data corruption using a serial terminal like HTerm. *Pass Criteria: Zero packet loss or bit errors over a 10-minute continuous run.

Failure Mode Analysis (FMA): *Procedure: Physically disconnect an Edge Node while the Hub is running. *Pass Criteria: Central Hub must immediately report a "Comms Failure" and enter a Fail-Closed state for all locks/actuators.

System Integration (Environmental Stress): *Procedure: Subject the Edge Node to a localized heat source (e.g., heat gun) or VOC spike. *Pass Criteria: Hub must trigger the cooling relay and deny access credentials within 1 second of the threshold breach.

TO be CONTINUED

Stay tuned for UPDATES

Thanks Skruglewicz