# Mirror HUD Display - ESP32 (SPI Interface)

ESP32-based mirror display for EUC battery and speed data via BLE.

## Hardware Configuration

### Waveshare 1.51" Transparent OLED (SSD1309)
- **Interface**: SPI (4-wire)
- **Resolution**: 128x64
- **Controller**: SSD1309

### Wiring for Standard ESP32 DevKit (SPI Interface)

| OLED Pin | ESP32 Pin | Description |
|----------|-----------|-------------|
| VCC      | 3.3V      | Power Supply |
| GND      | GND       | Ground |
| CLK      | GPIO 18   | SPI Clock (SCK) |
| DIN      | GPIO 23   | SPI Data (MOSI) |
| RES      | GPIO 16   | Reset |
| DC       | GPIO 17   | Data/Command |
| CS       | GPIO 5    | Chip Select |

### Pin Configuration

```cpp
#define OLED_CLK  18   // SPI Clock (SCL/SCK)
#define OLED_MOSI 23   // SPI Data (SDA/MOSI) 
#define OLED_RES  16   // Reset
#define OLED_DC   17   // Data/Command
#define OLED_CS   5    // Chip Select
```

## BLE Configuration

- **Device Name**: `mirror-hud`
- **Service UUID**: `12345678-1234-1234-1234-123456789abc`
- **Battery Characteristic**: `87654321-4321-4321-4321-cba987654321`
- **Speed Characteristic**: `11111111-2222-3333-4444-555555555555`

## Build & Upload

```bash
# Navigate to project
cd /Users/seb/euc/mirror-display

# Build for ESP32
pio run

# Upload and monitor
pio run --target upload --target monitor
```

## Display Behavior

### Boot Sequence
1. **Power on**: Shows "tangerine" in large text with border
2. **BLE Ready**: Shows "tangerine" with connection status
3. **Data Received**: Switches to EUC HUD display

### Data Display Layout
```
┌─────────────────────────────┐
│              CONN           │
│         EUC HUD             │
│                             │
│       25.4  km/h            │
│                             │
│ Batt: 85.2% [████████░░]    │
└─────────────────────────────┘
```

## Troubleshooting

### SPI Connection Issues
- Verify all 7 wire connections (VCC, GND, CLK, DIN, RES, DC, CS)
- Check 3.3V power supply (not 5V!)
- Ensure ESP32 SPI pins are correct (18, 23, 5, 16, 17)
- Try different ESP32 board if issues persist

### Display Issues
- Serial monitor shows SPI initialization steps
- Look for "✓ U8g2 SPI initialization successful!"
- Check for "SPI OLED should now show 'tangerine'!" message

### Common SPI Wiring Mistakes
- **CLK/DIN swapped**: Double-check GPIO 18 (CLK) and GPIO 23 (DIN)
- **Missing DC/CS**: Data/Command and Chip Select are required
- **Power issues**: Must use 3.3V, not 5V
- **Loose connections**: SPI requires all connections to be solid

## Alternative Pin Configuration

If default pins don't work, try:
```cpp
#define OLED_CLK  14   // Alternative SPI Clock
#define OLED_MOSI 13   // Alternative SPI Data
#define OLED_CS   15   // Alternative Chip Select
#define OLED_DC   2    // Alternative Data/Command
#define OLED_RES  4    // Alternative Reset
```