ESP32 + OLED Display: Display Weather from Home Assistant

Ever wanted a sleek, always-on display showing the current weather right from your Home Assistant dashboard? I did—and after some tinkering, I built one using an ESP32 and a tiny OLED screen. In this guide, I’ll walk you through the process, sharing pitfalls I encountered (like why my first attempt showed gibberish instead of temperatures) and how to avoid them.

Why This Project?

I love having ambient displays around my home that show useful info without needing to open an app. An ESP32 paired with an OLED is perfect for this: it’s cheap, energy-efficient, and easy to customize. Plus, pulling data from Home Assistant means you can display anything—not just weather.

What You’ll Need

Here’s the hardware and software I used:

• Hardware:

  • ESP32 development board (any variant will work)
  • 0.96" I2C OLED display
  • Breadboard and jumper wires
  • USB cable for power/flashing

• Software:

  • Home Assistant (already set up)
  • ESPHome (for ESP32 firmware)
  • Arduino IDE (optional, for troubleshooting)

Step 1: Wiring the ESP32 and OLED

The OLED uses I2C communication, so connect it to the ESP32 as follows:

Step 2: Setting Up ESPHome in Home Assistant

1. Install ESPHome via Home Assistant’s Add-on Store if you haven’t already.
2. Create a new ESPHome device for your ESP32. Here’s the base configuration (esp32-weather-display.yaml):

esphome:
  name: esp32-weather-display
  platform: ESP32
  board: nodemcu-32s

wifi:
  ssid: !secret wifi_ssid
  password: !secret wifi_password
  ap: {}

api:
  encryption:
    key: !secret api_key

ota:
  password: !secret ota_password

i2c:
  sda: 21
  scl: 22
  scan: true

font:
  - file: "gfonts://Roboto"
    id: roboto
    size: 12

display:
  - platform: ssd1306_i2c
    model: "SSD1306 128x64"
    address: 0x3C
    lambda: |-
            it.printf(0, 0, roboto, "Loading...");

3. Flash the ESP32 via USB. If all goes well, it’ll connect to Wi-Fi and show “Loading…” on the OLED.

Step 3: Fetching Weather Data from Home Assistant

Now, let’s modify the ESPHome config to display weather data. Assuming you’re using Home Assistant’s built-in weather integration:

sensor:
  - platform: homeassistant
    name: "Outside Temperature"
    entity_id: weather.your_weather_entity
    attribute: temperature
    id: temp_outside
  - platform: homeassistant
    name: "Weather Condition"
    entity_id: weather.your_weather_entity
    attribute: condition
    id: weather_condition

display:
  - platform: ssd1306_i2c
    model: "SSD1306 128x64"
    address: 0x3C
    lambda: |-
      it.printf(0, 10, roboto, "Temp: %.1f°C", id(temp_outside).state);
      it.printf(0, 30, roboto, "Condition: %s", id(weather_condition).state.c_str());      

Replace weather.your_weather_entity with your actual weather entity (e.g., weather.openweathermap).

Step 4: Customizing the Display

Want to make it prettier? Here’s how to add icons and dynamic formatting:

lambda: |-
  // Display temperature
  it.printf(0, 10, roboto, "🌡️ %.1f°C", id(temp_outside).state);
  
  // Map weather conditions to icons
  std::string condition = id(weather_condition).state;
  if (condition == "sunny") {
    it.printf(0, 30, roboto, "☀️ %s", condition.c_str());
  } else if (condition == "rainy") {
    it.printf(0, 30, roboto, "🌧️ %s", condition.c_str());
  } // Add more conditions as needed  

Troubleshooting

Problem: OLED stays blank after flashing.
Fix:

• Double-check I2C wiring (SDA/SCL).
• Run i2c_scanner in Arduino IDE to confirm the OLED address (often 0x3C or 0x3D).

Problem: Weather data doesn’t update.
Fix:

• Ensure the entity_id in ESPHome matches your Home Assistant weather entity.
• Restart both Home Assistant and the ESP32.

Going Further

• Add indoor temperature/humidity using an AHT10 sensor (see my ESP32 temperature monitoring guide).
• Make it battery-powered for portable use.
• Use multiple screens to cycle through stats like air quality or calendar events.

FAQ

Q: Can I use a bigger OLED display?
A: Absolutely! Just adjust the model in the ssd1306_i2c config (e.g., SSD1306 128x32).

Q: Why is my ESP32 overheating?
A: If you’re powering it via USB, overheating is rare. If using a battery, add a deep_sleep interval to conserve power.

Q: Can I display other Home Assistant data?
A: Yes! Any sensor or attribute can be fetched. Try sensor.indoor_temperature or binary_sensor.door_window.