Network Configuration

This guide covers how to connect your UltimateSensor to your network via WiFi or Ethernet, and how to switch between them.

Quick Overview

Your UltimateSensor ships with WiFi firmware pre-installed. Most users can simply use WiFi and never need to change anything.

WiFi Setup

Initial WiFi Configuration

When your UltimateSensor powers on for the first time (or after a factory reset), it creates a WiFi hotspot:

1. Look for the hotspot:

   • SSID: ultimatesensor
   • Password: ultimatesensor

2. Connect and configure:

   • Connect your phone/laptop to the ultimatesensor network
   • A captive portal should open automatically
   • Select your home WiFi network and enter the password
   • The UltimateSensor will restart and connect to your network

3. If the captive portal doesn't open:

   • Open a browser and go to http://192.168.4.1/
   • Configure your WiFi from there

WiFi Requirements

• 2.4 GHz network (5 GHz is not supported)
• WPA2 or WPA3 security
• Good signal strength at the installation location

WiFi Tips

• Check signal strength at the mounting location before installation
• If signal is weak, consider using Ethernet instead
• The UltimateSensor will automatically reconnect if WiFi is temporarily lost
• Fallback hotspot appears after 1 minute if WiFi connection fails

Ethernet Setup

Ethernet provides a more reliable connection and allows you to use Power over Ethernet (PoE) for a single-cable installation.

Ethernet Requirements

Before switching to Ethernet, ensure:

• ✅ DHCP enabled: Your network must assign IP addresses automatically
• ✅ Same VLAN: UltimateSensor must be on the same network/VLAN as Home Assistant
• ✅ No firewall blocking: Allow traffic between UltimateSensor and Home Assistant
• ✅ PoE switch (optional): If using PoE, you need an 802.3af compliant switch or injector

Switching to Ethernet

To switch from WiFi to Ethernet firmware, you have three options:

Quick overview:

• Option 1: Flash Ethernet firmware via USB-C before installation
• Option 2: Change UltimateSensor Firmware Variant in Home Assistant to an Ethernet option. The device installs the firmware over WiFi by itself
• Option 3: During first setup, choose Ethernet on the setup page and still enter your WiFi details. The device uses WiFi once to install the Ethernet firmware

⚠️ Important: Options 2 and 3 take at least 2 minutes, so keep the device powered. WiFi stops working as soon as the Ethernet firmware has started. Connect the Ethernet cable before switching or right after the restart.

📖 Full instructions: See Firmware Guide - Switching Variants, or Method 3: USB-C Web Flasher for USB flashing.

After Switching to Ethernet

• The UltimateSensor will get a new IP address via DHCP
• Home Assistant should auto-discover the device
• If not found, check your router's DHCP leases for the new IP
• Add the ESPHome integration manually if needed

Switching Back to WiFi

If you're on Ethernet and want to switch back to WiFi, you'll need to flash via USB-C.

📖 Full instructions: See the Firmware Guide - Method 3: USB-C Web Flasher for detailed flashing steps.

Quick overview:

1. Flash WiFi firmware via USB-C (V1: remove LD2450 sensor first)
2. Select WiFi + Basic/Complete variant
3. Device will create WiFi hotspot for configuration

Note: Ethernet firmware has no setup page and does not switch variants by itself. The update entity only offers WiFi firmware when it has a newer version than the installed one, so USB-C is the reliable way back.

Network Communication & Privacy

100% Local Operation

The UltimateSensor works completely locally. All sensor data stays on your local network:

• ✅ CO₂ measurements → Local
• ✅ Temperature, humidity → Local
• ✅ Particulate matter (Complete) → Local
• ✅ mmWave presence detection → Local
• ✅ VOC, NOx, light sensors → Local
• ✅ Home Assistant communication → Local
• ✅ Automations → Local

External Communication

The local firmware only goes online for these two things:

No sensor data is ever sent externally. The update check only retrieves a version number. Cloud firmware is the exception: it sends your measurements to the SmartHomeShop App.

Disabling Update Checks

If you want to disable even the version checks:

1. Adopt the device in ESPHome Device Builder
2. Add the update: block from Use UltimateSensor v1 without internet access
3. Install the firmware again

Troubleshooting

WiFi Issues

Can't find the UltimateSensor hotspot

• Wait 1-2 minutes after powering on
• The hotspot only appears if WiFi is not configured
• Look for the ultimatesensor network name
• If the device was configured before, the hotspot appears about 1 minute after it fails to reach your WiFi

Connected to hotspot but no captive portal

• Open browser manually to http://192.168.4.1/
• Try a different device (phone vs laptop)
• Disable mobile data on your phone

WiFi connection fails

• Verify you're using a 2.4 GHz network (not 5 GHz)
• Check WiFi password is correct
• Use WPA2 or WPA3 on your router. If a WPA3-only network does not connect, switch to mixed WPA2/WPA3
• Check signal strength at installation location

Frequent disconnections

• Check WiFi signal strength
• Move router/access point closer
• Reduce interference from other devices
• Consider switching to Ethernet for reliability

Ethernet Issues

Switched to Ethernet but device is offline

Cause: WiFi stopped immediately but Ethernet wasn't connected.

Solution:

1. Connect an Ethernet cable to the UltimateSensor
2. Check that the cable goes to a switch with DHCP
3. Verify same VLAN as Home Assistant
4. Check Ethernet port LED is lit (solid or blinking)
5. Device should appear in Home Assistant

If Ethernet is not possible: Flash WiFi firmware via USB-C (see Firmware Guide)

Ethernet connected but not discovered

Check:

1. Link lights on the Ethernet port (should be blinking)
2. Router DHCP leases for new device
3. Same VLAN as Home Assistant
4. No firewall blocking mDNS or ESPHome API

Manual connection:

1. Find the IP in your router's DHCP lease table
2. In Home Assistant, add ESPHome integration manually by IP

Device not getting IP address

• Verify DHCP is enabled on your network
• Check Ethernet cable and port
• Try a different switch port
• Try a different Ethernet cable
• Verify PoE is working (if using PoE), or try USB-C power instead

PoE not working

• Ensure your switch supports 802.3af PoE standard
• Check PoE is enabled on the switch port
• Try a different PoE port
• Test with USB-C power to isolate power issues

General Network Issues

Device shows offline in Home Assistant

1. Check power supply (OLED display should light up on boot)
2. Verify network connection (WiFi signal or Ethernet link)
3. Check if device is on same network as Home Assistant
4. Try pinging the device IP
5. Restart the device (disconnect/reconnect power)

Can't connect to device web interface

The UltimateSensor has a built-in web server at http://[device-ip]/:

• Works on both WiFi and Ethernet
• Shows sensor values and basic info
• Useful for debugging without Home Assistant
• If you can't access it, check network connectivity

Device has wrong IP address

If the device got an unexpected IP:

• Check your DHCP server configuration
• Set a DHCP reservation for the device (use MAC address)
• Verify no IP conflicts on your network

Advanced: Static IP Configuration

If you need a static IP instead of DHCP, you can configure it in ESPHome:

1. Open ESPHome in Home Assistant
2. Edit your UltimateSensor configuration
3. Add static IP configuration:

For WiFi:

wifi:
  manual_ip:
    static_ip: 192.168.1.100
    gateway: 192.168.1.1
    subnet: 255.255.255.0

For Ethernet:

ethernet:
  manual_ip:
    static_ip: 192.168.1.100
    gateway: 192.168.1.1
    subnet: 255.255.255.0

4. Click Save → Install → Wirelessly

⚠️ Warning: Make sure the IP address is outside your DHCP range and not already in use!

Need Help?

• Check the Firmware Guide for flashing instructions
• Check the Troubleshooting page for more issues
• Check the FAQ for common questions
• Join our Discord community
• Contact us via smarthomeshop.io/contact