euc-hud

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

#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

# 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:

#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