Departure Monitor for Lilygo T5 4.7" S3 E-Ink

A battery-powered departure monitor built for the Lilygo T5 4.7" S3 V2.4 E-Ink display (ESP32-S3).

The device connects to a public transport API over Wi-Fi, fetches upcoming departures for two stops, and displays them on the E-Paper screen. After each update the ESP32 goes into deep sleep to save power. It is designed to hang near the front door so the next bus or train is visible at a glance.

Features

• Wi-Fi connection with automatic NTP time synchronization
• Support for public transport APIs:
  • transport.rest (BVG Berlin, VBB, DB, ...)
  • VRR EFA rapidJSON (e.g. Castrop-Rauxel)
• Two separate stop sections on one screen
  • Top section: bus stop (e.g. Wesselstraße)
  • Bottom section: train station (e.g. Castrop-Rauxel Hbf)
• Per-stop line and direction filters
• Per-line next-departure selection for the train station, so S2 / RE3 / RB32 are always shown
• Displays line, destination, remaining minutes and delay
• Vehicle-type icons (bus / train) in front of each departure
• Imminent departures (≤ 5 min) highlighted with an inverted box
• "Now" for departures in less than one minute
• Delay shown as a compact +x badge
• Last update time shown top-right; timestamp turns gray when data is older than 10 minutes
• Battery level indicator in the header
• Low-battery mode: updates every 10 minutes when charge drops below 20%
• Detailed error screens (WiFi / NTP / API / no data)
• Day/night mode:
  • Day (05:00–21:00): updates every 3 minutes
  • Night (21:00–05:00): shows a decorative star/moon/landscape "Offline" screen and sleeps in 2-hour intervals until morning
• E-Ink display with 4 gray levels (960 × 540 px)
• Deep sleep between updates with Wi-Fi and Bluetooth powered down
• Fits in a custom 3D-printed case

Project Structure

.
├── include/
│   ├── config.h          # Stops, API, intervals
│   ├── secrets.h         # Wi-Fi credentials (not tracked by Git)
│   ├── departure.h       # Departure data structure
│   ├── departure_api.h   # API client
│   ├── display_manager.h # Display wrapper
│   ├── battery_manager.h # Battery voltage reading
│   └── wifi_manager.h    # Wi-Fi helper
├── src/
│   ├── main.cpp          # Main flow
│   ├── config.cpp        # Line / direction filters
│   ├── battery_manager.cpp
│   ├── departure_api.cpp
│   ├── display_manager.cpp
│   └── wifi_manager.cpp
├── platformio.ini        # PlatformIO configuration
└── README.md

Requirements

• Python 3
• The project includes PlatformIO in a local virtual environment (.venv)
• Lilygo T5 4.7" S3 V2.4 E-Ink board
• USB-C cable

Configuration

Open include/config.h and adjust at least the following values.

VRR EFA (default, e.g. Castrop-Rauxel)

#define API_TYPE       API_VRR_EFA
#define API_BASE_URL   "https://openservice-test.vrr.de/openservice"

#define STOP1_PLACE    "Castrop-Rauxel"
#define STOP1_ID       "Wesselstraße"
#define STOP2_PLACE    "Castrop-Rauxel"
#define STOP2_ID       "Hbf"

transport.rest (e.g. BVG Berlin)

#define API_TYPE       API_TRANSPORT_REST
#define API_BASE_URL   "https://v6.bvg.transport.rest"

#define STOP1_ID       "900000100003"
#define STOP2_ID       "..."

Wi-Fi

Create include/secrets.h with your credentials (this file is ignored by Git):

#ifndef WIFI_SSID
#define WIFI_SSID "YOUR_WIFI_SSID"
#endif

#ifndef WIFI_PASSWORD
#define WIFI_PASSWORD "YOUR_WIFI_PASSWORD"
#endif

If include/secrets.h is missing, you can also fill in the fallback values directly in include/config.h.

Line and direction filters

Filters are defined in src/config.cpp:

// Stop 1: Wesselstraße
const char* STOP1_LINES[] = {"482", "E482"};
const char* STOP1_EXCLUDE_DIRECTIONS[] = {"Dortmund", "Ickern"};

// Stop 2: Castrop-Rauxel Hbf
const char* STOP2_LINES[] = {"S2", "RE3", "RB32"};
const char* STOP2_DIRECTIONS[] = {"Essen", "Düsseldorf", "Duisburg", "Oberhausen"};

Build & Flash

From the project directory:

# Build
.venv/Scripts/pio run

# Upload (connect board via USB-C)
.venv/Scripts/pio run --target upload

# Serial Monitor
.venv/Scripts/pio device monitor

VRR EFA API Notes

• The default API_BASE_URL is the VRR OpenService test server. It can be used without registration for hobby/test purposes.
• For permanent or public use you should request access to the production server by sending a short project description to opendata-oepnv@vrr.de.
• The test server URL may change or be restricted without notice.

API Usage / Responsibility

This project does not include its own backend or API proxy. If you want to use it, you have to take care of the public-transport API yourself:

• VRR EFA: the built-in test URL works for experimentation, but for a permanent installation you must register with VRR (see above) and switch to the production endpoint.
• transport.rest: each provider (BVG, VBB, DB, ...) runs its own instance. Check the respective terms of use, rate limits, and availability. Some may require registration or API keys.
• Always respect the provider's terms of service and rate limits. The device fetches data directly from the configured API, so excessive polling can get your IP blocked.
• The default stops (Wesselstraße, Castrop-Rauxel Hbf) and line filters are only examples. Replace them with the stops and lines relevant for your location in include/config.h and src/config.cpp.

Power Saving

• The ESP32 enters deep sleep after every update.
• Wi-Fi and Bluetooth are powered down during sleep.
• The E-Ink screen only consumes power while updating.
• Intervals are configured in include/config.h:
  • DAY_INTERVAL_SEC: update interval during the day (default 180 s)
  • NIGHT_INTERVAL_SEC: sleep interval at night (default 7200 s)
  • NIGHT_START_HOUR / NIGHT_END_HOUR: night-mode window (default 21:00–05:00)

Troubleshooting

• Display stays black: open the Serial Monitor and check if Wi-Fi and API are connecting.
• Wi-Fi does not connect: check SSID and password in include/secrets.h (case-sensitive).
• API returns no data: verify STOP_ID / STOP_PLACE. The VRR test API can occasionally be slow or return empty results.
• Stuck in night mode: the timezone is set to CET-1CEST with automatic DST. Make sure NTP can sync after a reset.

License

MIT