# Presence Sensor - PoE Variant

Same sensors as the USB-C version, but powered and networked via Power over Ethernet (802.3af).

## Key Differences from USB-C Version

| Feature | USB-C Version | PoE Version |
|---------|--------------|-------------|
| Power | USB-C 5V | 802.3af PoE (48V → 5V) |
| Network | WiFi only | Ethernet (wired) + WiFi fallback |
| Connector | USB-C | RJ45 |
| Extra chips | None | W5500 (Ethernet) + AG9905MT (PoE PD) |
| Board size | 45x35mm | 50x40mm (RJ45 is bulky) |
| Reliability | WiFi dependent | Wired, rock-solid |
| Cost | ~$32 | ~$42 |

## Why PoE is Better for Cameras

- **No WiFi congestion** - camera streams are bandwidth-heavy
- **Single cable** - power + data in one Ethernet run
- **More reliable** - no WiFi dropouts
- **Centralized power** - PoE switch manages all device power
- **Remote reboot** - cycle PoE port to hard-reset device

## New Components

### W5500 Ethernet Controller
- SPI interface to ESP32-S3
- 10/100 Mbps Ethernet
- Hardware TCP/IP stack (offloads ESP32)
- QFP-48 package (7x7mm)
- JLCPCB: C32843

### RJ45 with Integrated Magnetics + PoE
- HR911105A or equivalent
- Includes PoE center-tap connections
- Through-hole (adds height but very robust)

### PoE PD Module - Silvertel Ag9905MT
- IEEE 802.3af compliant (up to 13W)
- 48V input → 5V/2A output
- Tiny module: 16.5x14.5mm
- Isolated, protected
- Alternative: AG9905M-R or TI TPS2376 discrete

### 25MHz Crystal Oscillator
- Required by W5500
- 3.2x2.5mm SMD package

## GPIO Changes for PoE Variant

| GPIO | USB-C Version | PoE Version |
|------|--------------|-------------|
| GPIO19 | USB D- | **Free** (no USB) |
| GPIO20 | USB D+ | **Free** (no USB) |
| GPIO33 | Free | **W5500 SPI MISO** |
| GPIO34 | Free | **W5500 SPI MOSI** |
| GPIO35 | Free | **W5500 SPI SCK** |
| GPIO36 | Free | **W5500 SPI CS** |
| GPIO37 | Free | **W5500 INT** |
| GPIO42 | Free | **W5500 RST** |

Camera, mmWave, PIR, I2C sensors - all unchanged.

## Power Path

```
PoE Switch (48V)
    │
    ▼
RJ45 Connector (center-taps)
    │
    ▼
Ag9905MT PoE PD Module
    │ (48V → 5V isolated)
    ▼
5V Rail ──→ LD2410C (direct)
    │
    ▼
AMS1117-3.3
    │
    ▼
3.3V Rail ──→ ESP32-S3, W5500, sensors, camera LDOs
```

## Power Budget (PoE)

| Component | Voltage | Current |
|-----------|---------|---------|
| ESP32-S3 | 3.3V | 240mA |
| W5500 | 3.3V | 132mA |
| OV5640 | 2.8V+1.8V | 140mA |
| LD2410C | 5V | 60mA |
| AM312 + SHT41 + BH1750 | 3.3V | 3mA |
| Ag9905MT overhead | - | ~50mA |
| **Total from PoE** | 48V | **~180mA @ 48V (~8.6W)** |

Well within 802.3af's 12.95W limit.

## Board Layout Notes

- RJ45 connector at bottom (cable exits down for wall mount)
- Ag9905MT module near RJ45 (short high-voltage traces)
- W5500 between RJ45 and ESP32 (short SPI traces)
- Camera at top (unchanged)
- mmWave on right (unchanged)
- PIR on left (unchanged)
- Sensors on left edge (unchanged)
- Board slightly larger: 50x40mm to accommodate RJ45 jack height