SmartHomeShop Docs

Troubleshooting

Rapidly flashing red status LED on a VLAN without internet

If your UltimateSensor v1 continues to report measurements but its red status LED flashes rapidly after startup, the firmware update check may be blocked by your firewall or IoT VLAN.

The local UltimateSensor v1 firmware reads a small version manifest from SmartHomeShop GitHub Pages. This check only determines whether new firmware is available. It does not send sensor readings, Home Assistant data, Wi-Fi passwords or API keys to GitHub.

ESPHome's standard status LED reports errors from every firmware component. A blocked update check can therefore look like a device startup error even while UltimateSensor v1 itself is working normally.

Confirm the cause

Open the UltimateSensor v1 logs in ESPHome and look for http_request.update or Failed to fetch manifest. If these messages are not present, investigate power, network and sensor initialization before changing the update settings.

Disable scheduled firmware checks

  1. Open the ESPHome Device Builder app/add-on in Home Assistant. This is different from the ESPHome integration under Settings > Devices & services.
  2. Find UltimateSensor v1 and select Take control or Adopt.
  3. Save a copy of the generated YAML, including its API encryption key.
  4. Select Edit and add this block at the bottom of the YAML, without extra indentation:
update:
  - id: !extend firmware_update
    update_interval: never
  1. Save the file, select Validate, and then select Install > Wirelessly.

After installation, UltimateSensor v1 keeps measuring and communicating locally with Home Assistant, but it no longer performs scheduled firmware checks. You can still update it later through ESPHome or the SmartHomeShop web flasher.

ESPHome still downloads the UltimateSensor v1 packages: configuration from GitHub while compiling. That request is made by the Home Assistant/ESPHome host, not by UltimateSensor v1 itself.

If validation says that firmware_update does not exist, remove the block again and install a current UltimateSensor v1 firmware version first. A rapidly flashing LED that remains after this change can indicate another real firmware or hardware error.

This guide helps you resolve common issues with your UltimateSensor.

General Troubleshooting Steps

Before diving into specific issues, try these steps:

  1. Check Power Connection

    • Ensure USB-C cable is securely connected
    • Try a different power adapter (minimum 1A)
    • If using PoE, verify the switch/injector is working

  2. Restart the Device

    • Unplug power, wait 10 seconds, reconnect
    • Or use the "Restart UltimateSensor" button in Home Assistant

  3. Check Home Assistant

    • Restart Home Assistant: Settings → System → Restart
    • Update Home Assistant to the latest version

  4. Verify Network Connection

    • Check if device appears in your router's DHCP list
    • Ensure device is on same network/VLAN as Home Assistant

WiFi Connectivity Issues

Can't Find the WiFi Hotspot

The ultimatesensor hotspot should appear after powering on:

  • Wait 1-2 minutes: it takes time to initialize
  • Hotspot only appears if WiFi isn't already configured
  • Try different devices: some phones/laptops see it better than others
  • Factory reset if previously configured (see below)

Connected to Hotspot but No Captive Portal

If the configuration page doesn't open automatically:

  1. Open a browser manually
  2. Navigate to http://192.168.4.1/
  3. Try disabling mobile data on your phone
  4. Try a different browser

WiFi Won't Connect

  • 2.4 GHz only: 5 GHz networks are not supported
  • Check password: WiFi passwords are case-sensitive
  • Signal strength: move closer to router during setup
  • Special characters: some special characters in SSID/password may cause issues

Frequent Disconnections

  • Check signal strength at the sensor location
  • Reduce interference from other 2.4 GHz devices
  • Consider Ethernet for more stable connectivity
  • Check router settings: some routers disconnect idle devices

Fallback Hotspot Mode

If the UltimateSensor can't connect to WiFi, it automatically creates a fallback hotspot after 1 minute:

  • SSID: ultimatesensor
  • Password: ultimatesensor

Connect to reconfigure WiFi settings.

Ethernet/PoE Issues

Ethernet Not Working

  1. Check firmware: Ethernet requires Ethernet firmware (see Firmware Guide)
  2. LED check: Yellow/green LED on Ethernet port indicates active connection
  3. Cable check: Try a different Ethernet cable
  4. DHCP: Ensure DHCP is enabled on your network
  5. No VLANs: Initially test without VLAN segmentation

PoE Not Powering Device

  • Verify PoE standard: IEEE 802.3af compatible required
  • Check PoE budget: Switch may have limited power budget
  • Try USB-C power with Ethernet cable (non-PoE) to test

Switching Firmware Issues

When switching between WiFi and Ethernet firmware:

  • WiFi → Ethernet: Connect Ethernet cable BEFORE switching
  • Ethernet → WiFi: Requires USB-C flashing (see Firmware Guide)
  • Device disappears: Check DHCP client list for new IP address

Sensor Data Issues

Sensors Not Updating

  • Startup time: Sensors need 10+ minutes to stabilize
  • CO₂ specifically: May take 24-48 hours for accurate readings
  • Check entities: Some may be disabled by default in Home Assistant

Inaccurate CO₂ Readings

  • Initial calibration: Wait at least 24 hours
  • Placement: Avoid heat sources and direct sunlight
  • Manual calibration: Place outdoors, use "CO2 manual calibration" button
  • See Calibration Guide for details

Temperature Reading High

The SCD41 sits inside the enclosure where components generate heat:

  • Expected offset: 2-5°C higher than ambient
  • Solution: Apply negative offset in ESPHome configuration
  • See Calibration Guide for instructions

mmWave False Positives

The radar may detect movement through walls or from moving objects:

  • Shrink your polygon zones so they end at the wall
  • Draw an exclusion zone over the problem area in the Room Designer
  • Check for moving objects (fans, curtains, pets)
  • Check for reflections from mirrors and large metal surfaces

mmWave Not Detecting

  • Check positioning: front of device must face the monitored area
  • Verify entity states: check the Target X Distance values
  • Timeout: Tracking Presence Timeout sets how long presence stays on after the last detection
  • Zones: check that Polygon Zones Enabled is on and that the zone is in the right place

PIR Not Triggering

  • Check entity: PIR Sensor binary sensor in Home Assistant
  • Line of sight: PIR requires direct view of movement
  • Temperature difference: PIR detects heat, may miss cold-handed people

PM Sensor No Data (Complete Only)

  • Startup time: SPS30 needs time to initialize
  • Check firmware: Must be using "Complete" firmware variant
  • Measurement cycle: With the default SPS30 Idle Interval of 5 minutes the sensor pauses between measurements. Set it to 0 to measure continuously
  • Switches: Check that PM Sensor is on and Night Mode is off. The sensor also stops during SPS30 Quiet Hours

Display Issues

OLED Display Blank

  • Startup time: Display initializes after sensors
  • Reboot: Try power cycling the device
  • Brightness: Display is set to 40% contrast
  • Switch: Check that LCD Display is on. Night Mode also turns the display off

Display Shows Wrong Values

  • Sensor startup: Values stabilize after 10+ minutes
  • Display lag: Shows last known values if sensor fails

LED Indicator Issues

Red Status LED Flashing Slowly

Device is not connected to WiFi or Home Assistant:

  • Check WiFi configuration
  • Verify Home Assistant can reach the device
  • Check if device is in fallback hotspot mode

Red Status LED Flashing Rapidly

Startup error detected:

  • Try power cycling
  • Re-flash firmware if persistent
  • Check for hardware issues

Status LED on Cloud Firmware

Cloud firmware blinks the status LED while the device is offline and turns it off once it is online. On cloud firmware a blinking LED therefore points to the network connection.

Back LED Not Controllable

  • Check entity: Back Light light entity in Home Assistant
  • Automatic LED Lighting: While this switch is on, the firmware controls the LED itself

Home Assistant Integration Issues

Device Not Auto-Discovered

  1. Go to Settings → Devices & Services
  2. Click Add Integration
  3. Select ESPHome
  4. Enter the device's IP address (find in router DHCP list)

Entities Missing

  • Some entities are disabled by default (IP Address, Connected BSSID, the firmware update entity and more)
  • Go to device in Home Assistant, click entity, enable it

Device Offline in Home Assistant

  • Check network connectivity
  • Verify IP address hasn't changed
  • Firewall rules may be blocking communication
  • mDNS issues: Try using IP address instead of hostname

Advanced Troubleshooting

Accessing Web Interface

The UltimateSensor has a built-in web interface:

  1. Find device IP in your router's DHCP list
  2. Open browser and navigate to http://<device-ip>/
  3. View sensor values, logs, and device info

Viewing Logs

In ESPHome:

  1. Open ESPHome Device Builder
  2. Click on your UltimateSensor device
  3. Click "Logs" to see real-time output

Factory Reset

To completely reset the device:

  1. Follow Method 3: USB-C Web Flasher, including removing the LD2450
  2. Set up WiFi again through the ultimatesensor hotspot

This returns the device to its factory settings. WiFi credentials, zones and all other settings are erased.

Firmware Update

For OTA updates:

  • Use the UltimateSensor Firmware update entity in Home Assistant
  • Or, for an adopted device, click "Install" → "Wirelessly" in ESPHome Device Builder

For USB updates:

Network Communication & Privacy

100% Local Operation

The UltimateSensor works entirely locally:

  • ✅ All sensor data stays on your network
  • ✅ Home Assistant communication is local
  • ✅ Automations run locally

External Communication

The local firmware only goes online for:

  • Firmware version check on SmartHomeShop GitHub Pages
  • The time from an NTP server

Disabling Update Checks

Follow Disable scheduled firmware checks at the top of this page.

Still Having Issues?

If none of the above solutions work:

  1. Join Discord: smarthomeshop.io/discord, fastest support
  2. Contact us: smarthomeshop.io/contact
  3. Check GitHub: github.com/smarthomeshop/ultimatesensor

When asking for help, please include:

  • Hardware version (Basic/Complete)
  • Firmware version
  • Connection type (WiFi/Ethernet)
  • Description of the issue
  • Any error messages from logs