# ESP32-S3 RLCD 4.2 Indoor / Outdoor Temperature Display A simple, clean desktop temperature and clock display built around the **WaveShare ESP32-S3-RLCD-4.2**. The display is designed to make the information readable from a distance, with the current time occupying the upper half of the screen and indoor/outdoor temperatures displayed prominently across the lower half. ## Display Layout ![Display Sample](/documents/display_sample.png) The display uses the full 300 × 400 pixel resolution of the 4.2-inch reflective LCD. ### Display Sections **Top 50%** * Large digital time * Current date underneath * Time displayed in a very large, bold font * 24-hour format * Date displayed as: * Day of week * Day * Month **Bottom 50%** * Two equal-width temperature sections * Indoor temperature on the left * Outdoor temperature on the right * Large, bold temperature values * Temperature displayed in °C * Optional small labels above each temperature ## Hardware ### Main Controller / Display **WaveShare ESP32-S3-RLCD-4.2** The board provides: * ESP32-S3 dual-core LX7 processor * Up to 240 MHz * 16 MB Flash * 8 MB PSRAM * 2.4 GHz Wi-Fi * Bluetooth 5 LE * 4.2-inch reflective LCD * 300 × 400 pixel resolution * PCF85063 real-time clock * SHTC3 temperature/humidity sensor * TF card interface * USB Type-C * 18650 battery holder * RTC backup battery support The onboard SHTC3 provides the indoor temperature measurement. The PCF85063 provides hardware real-time clock functionality. See the official hardware documentation: [WaveShare ESP32-S3-RLCD-4.2 Documentation](https://docs.waveshare.com/ESP32-S3-RLCD-4.2?utm_source=chatgpt.com) ## Outdoor Temperature The outdoor temperature will be supplied separately from the display. The preferred architecture is: ```text Outdoor Sensor │ │ Wi-Fi ▼ ESP32-S3-RLCD-4.2 │ ├── Indoor Temperature ├── Outdoor Temperature ├── Date └── Time ``` The outdoor sensor can be another ESP32-based device, a network temperature sensor, MQTT source, HTTP API, or another compatible data source. The display should continue showing the last known outdoor temperature if the outdoor sensor temporarily becomes unavailable. ## Software The project is intended to run on the ESP32-S3 using the Arduino framework. ### Development Environment Recommended: * Visual Studio Code * PlatformIO * Arduino framework * ESP32-S3 board support WaveShare officially supports both Arduino IDE and ESP-IDF for this board. ## Proposed Software Architecture ```text ┌─────────────────────┐ │ ESP32-S3 │ │ │ │ Main Application │ └──────────┬──────────┘ │ ┌────────────────┼────────────────┐ │ │ │ ▼ ▼ ▼ ┌───────────┐ ┌───────────┐ ┌───────────┐ │ RTC │ │ SHTC3 │ │ Wi-Fi │ │ PCF85063 │ │ Indoor │ │ │ └─────┬─────┘ └─────┬─────┘ └─────┬─────┘ │ │ │ │ │ │ │ │ Outdoor Temp │ │ │ └────────────────┼────────────────┘ │ ▼ ┌──────────────────┐ │ Display Engine │ └────────┬─────────┘ │ ▼ ┌──────────────────┐ │ 300 × 400 RLCD │ └──────────────────┘ ``` ## Display Design The UI should remain intentionally simple. There should be no unnecessary menus, icons, animations, or small text. The primary purpose of the display is to provide information that can be read quickly from across a room. ### Time The time should be the largest element on the display. Example: ```text 11:08 ``` The seconds should not normally be displayed. The display should update once per minute. ### Date The date is positioned directly underneath the time. Example: ```text MONDAY 24 AUGUST ``` ### Indoor Temperature The indoor temperature comes from the onboard SHTC3 sensor. Example: ```text INDOOR 21.5°C ``` ### Outdoor Temperature The outdoor temperature is received over the network. Example: ```text OUTDOOR 14.8°C ``` ## Data Update Rates | Data | Source | Update Rate | | ------------------- | ------------ | ------------: | | Time | PCF85063 RTC | 1 minute | | Date | PCF85063 RTC | 1 day | | Indoor temperature | SHTC3 | 30–60 seconds | | Outdoor temperature | Network | 30–60 seconds | | Display | RLCD | As required | The display should avoid unnecessary full-screen refreshes. ## Network Behaviour On startup: 1. Initialise the display. 2. Initialise the RTC. 3. Read the onboard SHTC3 sensor. 4. Connect to Wi-Fi. 5. Obtain the current time. 6. Obtain the outdoor temperature. 7. Draw the complete display. During normal operation: 1. Update the RTC time. 2. Read the indoor temperature. 3. Check for a new outdoor temperature. 4. Update the display when required. If Wi-Fi is unavailable: * Continue displaying the time. * Continue displaying the indoor temperature. * Display the last known outdoor temperature. * Indicate that the outdoor reading is stale if required. ## Time Synchronisation The ESP32-S3 should synchronise the RTC from an NTP server when network connectivity is available. Recommended configuration: ```text NTP Server: pool.ntp.org Time Zone: Australia/Hobart Format: 24 hour ``` The RTC then maintains the time locally when Wi-Fi is unavailable. ## Temperature Display Temperatures should be displayed with one decimal place. Examples: ```text 21.5°C 19.0°C 7.8°C -2.3°C ``` The degree symbol should be displayed as: ```text °C ``` ## Error Handling ### No Wi-Fi The display continues operating from the local RTC. ```text OUTDOOR --.-°C ``` or, if a previous value is available: ```text OUTDOOR 14.8°C ``` The previous value should preferably remain visible rather than replacing it immediately with an error value. ### Sensor Error If the SHTC3 cannot provide a valid indoor temperature: ```text INDOOR --.-°C ``` ### RTC Error If the RTC has lost its valid time: ```text --:-- ``` The system should attempt to correct the time as soon as network connectivity becomes available. ## Project Structure A suggested project structure: ```text / ├── README.md ├── platformio.ini │ ├── src/ │ ├── main.cpp │ ├── display.cpp │ ├── display.h │ ├── rtc.cpp │ ├── rtc.h │ ├── temperature.cpp │ ├── temperature.h │ ├── network.cpp │ ├── network.h │ ├── outdoor.cpp │ └── outdoor.h │ ├── include/ │ ├── config.h │ └── secrets.h │ ├── lib/ │ └── data/ └── fonts/ ``` ## Configuration User-specific settings should be kept separate from the main application code. Example: ```cpp #define WIFI_SSID "YOUR_WIFI" #define WIFI_PASSWORD "YOUR_PASSWORD" #define NTP_SERVER "pool.ntp.org" #define TIMEZONE "Australia/Hobart" #define TEMP_UPDATE_MS 60000 #define DISPLAY_UPDATE_MS 60000 ``` Credentials should not be committed to the repository. A local configuration file should be added to `.gitignore`. ## Future Features Potential future additions: * MQTT outdoor temperature * Multiple outdoor sensors * Humidity display * Weather forecast * Weather icons * Indoor/outdoor humidity * Wi-Fi signal indicator * Battery percentage * Automatic screen brightness control * Configuration through a web interface * OTA firmware updates * Custom temperature units * Minimum/maximum temperature * Historical temperature logging * TF card data logging * Automatic night mode * Multiple display layouts ## Design Goals The project should follow these principles: 1. **Large, readable information** 2. **Minimal UI** 3. **Low power consumption** 4. **Reliable local timekeeping** 5. **Continued operation without Wi-Fi** 6. **Clear indoor/outdoor temperature separation** 7. **Fast display updates** 8. **Simple configuration** The WaveShare board is particularly suited to this application because the RLCD provides a reflective display without a conventional backlight, while the board already includes the RTC and indoor temperature/humidity sensor required by the application. ## Hardware Documentation Official documentation: [WaveShare ESP32-S3-RLCD-4.2](https://docs.waveshare.com/ESP32-S3-RLCD-4.2?utm_source=chatgpt.com) ## Licence This project is released under the terms specified by the repository owner.