# Hardware Reference

**Version**: 1.0.0
**Date**: 2026-06-26

## 1. Target Hardware

### 1.1 LW840X Module

The LW840X is an ESP32-based WiFi module designed for IoT applications.

| Specification | Value |
|---------------|-------|
| MCU | ESP32 (Xtensa LX7 dual-core) |
| Clock | 240 MHz |
| RAM | 520 KB SRAM |
| Flash | 4 MB (external) |
| WiFi | 802.11 b/g/n (2.4 GHz) |
| Bluetooth | None (LW840X) |
| GPIO | 20+ (depends on module) |
| ADC | 18 channels (12-bit) |
| Operating Temp | -40°C to +85°C |
| Voltage | 3.0V to 3.6V |

### 1.2 Pin Mapping

```
LW840X Module Pinout
┌─────────────────────────────────────┐
│                                     │
│  3V3  ─┐                           │
│  GND  ─┤                           │
│  EN   ─┤                           │
│  IO0  ─┤  Boot/Flash mode          │
│  IO1  ─┤  TX0 (UART0)             │
│  IO3  ─┤  RX0 (UART0)             │
│  IO4  ─┤  Status LED               │
│  IO5  ─┤  (reserved)               │
│  IO12 ─┤  (reserved)               │
│  IO13 ─┤  (reserved)               │
│  IO14 ─┤  (reserved)               │
│  IO15 ─┤  (reserved)               │
│  IO16 ─┤  (reserved)               │
│  IO17 ─┤  (reserved)               │
│  IO18 ─┤  (reserved)               │
│  IO19 ─┤  (reserved)               │
│  IO21 ─┤  (reserved)               │
│  IO22 ─┤  (reserved)               │
│  IO23 ─┤  (reserved)               │
│  IO25 ─┤  (reserved)               │
│  IO26 ─┤  (reserved)               │
│  IO27 ─┤  (reserved)               │
│  IO32 ─┤  (reserved)               │
│  IO33 ─┤  (reserved)               │
│  IO34 ─┤  (reserved)               │
│  IO35 ─┤  (reserved)               │
│                                     │
└─────────────────────────────────────┘
```

### 1.3 Minimal Circuit

```
Power Supply:
  3.3V ──── LW840X 3V3
  GND  ──── LW840X GND

Decoupling:
  100nF ceramic capacitor between 3V3 and GND (close to module)

Boot/Flash:
  IO0 ──── 10K pull-up to 3V3 (normal boot)
  IO0 ──── GND (flash mode)

Status LED:
  IO4 ──── 220Ω ──── LED ──── GND

UART (for debugging):
  IO1 (TX0) ──── USB-UART RX
  IO3 (RX0) ──── USB-UART TX
  GND        ──── USB-UART GND
```

## 2. Power Requirements

### 2.1 Current Consumption

| Mode | Current | Notes |
|------|---------|-------|
| Active (WiFi TX) | 130-170 mA | Transmitting data |
| Active (WiFi RX) | 80-100 mA | Receiving data |
| Modem Sleep | 15-20 mA | WiFi connected, low duty cycle |
| Light Sleep | 0.8-1.5 mA | CPU paused, WiFi wake |
| Deep Sleep | 5-10 µA | RTC only, wake on GPIO |
| Off | 0 µA | No power |

### 2.2 Power Supply Design

```
Recommended:
  Input: 5V USB or 12V DC
  Regulator: AMS1117-3.3 or similar LDO
  Capacity: 500mA minimum
  
  ┌─────────┐     ┌─────────┐     ┌─────────┐
  │ 5V USB  │────▶│  LDO    │────▶│ LW840X  │
  │         │     │ 3.3V    │     │         │
  └─────────┘     └─────────┘     └─────────┘
                      │
                     GND
```

### 2.3 Battery Operation

For battery-powered applications:

| Battery | Capacity | Runtime (Active) | Runtime (Sleep) |
|---------|----------|------------------|-----------------|
| CR2032 | 225 mAh | ~1.5 hours | ~2 years |
| 18650 | 3400 mAh | ~20 hours | ~30 years |
| LiPo 1000mAh | 1000 mAh | ~6 hours | ~10 years |

**Note**: Deep sleep with periodic wake (e.g., every 5 minutes) is recommended for battery operation.

## 3. Antenna Options

### 3.1 PCB Trace Antenna

- **Pros**: Low cost, compact
- **Cons**: Lower gain, sensitive to placement
- **Range**: 10-30m (indoor)
- **Use Case**: Short-range, cost-sensitive

### 3.2 U.FL Connector

- **Pros**: Higher gain, flexible placement
- **Cons**: Additional cost, larger size
- **Range**: 50-100m (indoor)
- **Use Case**: Longer range, industrial

### 3.3 External Antenna

- **Pros**: Best performance, directional options
- **Cons**: Highest cost, largest size
- **Range**: 100m+ (outdoor)
- **Use Case**: Outdoor, long-range

## 4. Development Board

### 4.1 ESP32-DevKitC

Recommended for development and prototyping.

| Feature | Specification |
|---------|---------------|
| MCU | ESP32-WROOM-32 |
| Flash | 4 MB |
| RAM | 520 KB SRAM |
| WiFi | 802.11 b/g/n |
| Bluetooth | BT 4.2 + BLE |
| USB | Micro-USB (CP2102) |
| GPIO | 38 pins |
| Price | ~$5-10 |

### 4.2 Flashing

```bash
# Install ESP-IDF
# https://docs.espressif.com/projects/esp-idf/en/latest/esp32/get-started/

# Set target
idf.py set-target esp32

# Build
idf.py build

# Flash (auto-detect port)
idf.py -p /dev/ttyUSB0 flash

# Monitor
idf.py -p /dev/ttyUSB0 monitor
```

### 4.3 Pin Connections (DevKit)

```
Status LED:
  GPIO4 ──── 220Ω ──── LED ──── GND

Debug UART (optional):
  GPIO1 (TX0) ──── USB-UART RX
  GPIO3 (RX0) ──── USB-UART TX
  GND          ──── USB-UART GND
```

## 5. Production Board

### 5.1 Design Guidelines

1. **Power**:
   - Use 3.3V LDO with 500mA capacity
   - Add 100nF ceramic capacitor close to 3V3 pin
   - Add 10µF tantalum capacitor for bulk decoupling

2. **Antenna**:
   - Keep antenna area clear of copper pours
   - Minimum 10mm clearance around antenna
   - Use U.FL connector for external antenna

3. **Layout**:
   - Route UART traces away from antenna
   - Keep crystal traces short
   - Ground plane under module

4. **Enclosure**:
   - Use non-metallic enclosure (plastic)
   - Ensure antenna is not shielded
   - Provide mounting holes

### 5.2 Bill of Materials (BOM)

| Component | Quantity | Package | Notes |
|-----------|----------|---------|-------|
| LW840X | 1 | Module | ESP32-based |
| AMS1117-3.3 | 1 | SOT-223 | 3.3V LDO |
| 100nF | 2 | 0402 | Decoupling |
| 10µF | 1 | 0805 | Bulk cap |
| 220Ω | 1 | 0402 | LED resistor |
| LED | 1 | 0603 | Status indicator |
| U.FL | 1 | SMD | Antenna connector |
| Header | 1 | 2.54mm | Debug UART |

### 5.3 Schematic

```
                    ┌─────────────────┐
                    │    LW840X       │
  3.3V ────────────┤ 3V3         GND ├──── GND
                    │                 │
  IO4 ──── 220Ω ───┤ IO4         TX0 ├──── UART RX
         └── LED ──┤             RX0 ├──── UART TX
              GND  │                 │
                   │             EN  ├──── 10K ──── 3.3V
                   │                 │
                   │             IO0 ├──── 10K ──── 3.3V
                   │                 │           (flash: GND)
                   └─────────────────┘
```

## 6. Testing & Validation

### 6.1 Hardware Tests

1. **Power-on Test**:
   - Verify 3.3V at module pin
   - Check current consumption (~50mA idle)
   - Confirm LED blinks on boot

2. **WiFi Test**:
   - Scan for WiFi networks
   - Connect to test AP
   - Measure RSSI at distance

3. **UART Test**:
   - Send AT commands (if firmware supports)
   - Verify debug output
   - Check baud rate (115200)

4. **Flash Test**:
   - Write/read NVS data
   - Verify flash size
   - Test wear leveling

### 6.2 Production Test

1. **Functional Test**:
   - Provision with test server
   - Verify WireGuard handshake
   - Check heartbeat response

2. **Stress Test**:
   - Run for 24+ hours
   - Monitor memory leaks
   - Verify reconnection after WiFi drop

3. **Environmental Test**:
   - Operating temperature range
   - Humidity resistance
   - Vibration resistance

## 7. Troubleshooting

### 7.1 Common Issues

| Symptom | Cause | Solution |
|---------|-------|----------|
| No boot | IO0 held low | Remove flash jumper |
| No WiFi | Antenna issue | Check antenna connection |
| High current | WiFi always on | Use modem sleep |
| Crash on boot | Stack overflow | Increase task stack size |
| Provision fail | Token expired | Get new token from server |

### 7.2 Debug Tools

- **Serial Monitor**: `idf.py monitor`
- **JTAG Debugger**: OpenOCD + GDB
- **Logic Analyzer**: Saleae or similar
- **Power Analyzer**: Monsoon or similar

## 8. Compliance

### 8.1 Certifications

- **FCC**: Required for US market
- **CE**: Required for EU market
- **IC**: Required for Canada market
- **TELEC**: Required for Japan market

### 8.2 Testing

- EMC testing (emissions and immunity)
- SAR testing (if applicable)
- Environmental testing (temperature, humidity)

## 9. References

- [ESP32 Hardware Design Guidelines](https://www.espressif.com/sites/default/files/documentation/esp32_hardware_design_guidelines_en.pdf)
- [ESP32 Datasheet](https://www.espressif.com/sites/default/files/documentation/esp32_datasheet_en.pdf)
- [LW840X Module Datasheet](link-to-datasheet)
- [ESP-IDF Programming Guide](https://docs.espressif.com/projects/esp-idf/)