CO2 Gadget WiFi Guide: Connection, Website and API

Last modified 5 days

Configuring the Wi-Fi on your Gadget CO₂ meter is the first step towards accessing the web interface, the REST API and OTA updates via your browser. In this guide, you’ll learn about the four available methods: the Sensirion MyAmbiance app, the captive portal, the serial menu and the preferences page.

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Wi-Fi is the communications hub of the CO2 Gadget. You can use it to access the web interface from any browser, use MQTT to send data to Home Assistant, receive remote commands, to do OTA updates and consume the REST API to integrate your CO₂ monitor with other home automation systems. All this without relying on third-party cloud services – something very few commercial monitors offer.

Here’s everything you need to set up the Wi-Fi on your CO2 Gadget.

Default Wi-Fi settings

As soon as you flash CO2 Gadget for the first time, the Wi-Fi comes on disabled. BLE (Bluetooth Low Energy) is indeed active, allowing you to set up the Wi-Fi via the Sensirion MyAmbiance app without needing any buttons or a screen. It’s that simple to have a high-quality CO₂ meter up and running in minutes.

ParameterValue
Wi-FiOFF
Hostname`CO2-Gadget`
DHCPEnabled (Automatic IP)
mDNSEnabled
Captive PortalEnabled (if no Wi-Fi is configured)

How to connect your CO₂ monitor to Wi-Fi

You have 4 ways To connect your CO₂ meter with CO2 Gadget to your Wi-Fi network, choose the option that suits you best:

1. From the MyAmbiance app (recommended)

  1. Install Sensirion MyAmbiance (iOS / Android) — it’s free
  2. Open the app and search for your device (`CO2-Gadget`)
  3. Go to Settings → Wi-Fi Configuration
  4. Enter your SSID and password
  5. The meter connects automatically

2. Captive portal (no app, no buttons)

If your meter Wi-Fi is not set up, when you switch it on for the first time, it creates its own network. Connect to it, and the captive portal will open automatically, allowing you to enter your network details. On iOS, if the portal doesn’t load, open Safari and go to http://192.168.4.1.

3. On-screen menu or via serial port

From the menu: Settings → Wi-Fi Settings → Wi-Fi Enable [ON]. Enter the SSID, password and hostname. Save by clicking Save Preferences.

4. Preferences webpage

If you’re already connected, you can switch networks from http://ipdelmeter/preferences.html

Web interface for your CO₂ meter

Once you’re connected, open http://CO2-Gadget.local in any browser. The CO2 Gadget web interface features an Apple-style design with automatic dark/light mode, something you won’t find on any other commercially available meter in this price range.

PageURLDescription
Home`/`CO₂, temperature and humidity dashboard
Charts`/charts.html`Historical data with Chart.js, CSV/JSON export
Calibration`/calibration.html`Live FRC forced calibration
Low Power`/low_power.html`Configuring low-power thresholds
Preferences`/preferences.html`All device settings
Status`/status.html`Version, RSSI, uptime and status
OTA`/update`Web-based firmware update

mDNS: name-based access

CO2 Gadget implements mDNS: Access your meter using its hostname, without having to find out its IP address: http://CO2-Gadget.local. Configurable in Settings → Wi-Fi Settings → Host.

REST API for professional integration

CO2 Gadget showcases a Full REST API to integrate your high-quality CO₂ meter with Home Assistant, Node-RED, Grafana and any other system. Commercial meters rarely offer such a comprehensive and well-documented API.

GET /readCO2 → 892 (ppm)
GET /readTemperature    → 24.5 (°C)
GET /readHumidity → 45.2 (%)
GET /status → Full system JSON
GET /settings?Param=Val → Change any setting
POST /savePreferences   → Save multiple parameters

Static IP for your meter

Set up a static IP address from /preferences.html → active Use a static IP address and enter the IP address, subnet mask, gateway and DNS. Ideal for integration with Home Assistant.

Safety

Password fields are disabled by default because they are transmitted in plain text. Add ?relaxedSecurity=true to the URL to enable them. During compilation, enable WIFI_PRIVACY to hide passwords via the serial port.

WiFi troubleshooting

ProblemSolution
It won't connect to the Wi-FiCheck the SSID and password (max. 63 characters)
It switches off randomlyWeak signal – move the router closer or use a repeater
.local isn't workingIf mDNS is blocked on your network, use the IP address directly
Captive portal won't load on iOSOpen Safari and type http://192.168.4.1

Important notes

  • Wi-Fi can be switched on or off without restarting the meter
  • In LOW_POWER mode, Wi-Fi connects only every N cycles to save battery life
  • CO2 Gadget only supports 2.4 GHz networks (the ESP32 does not support 5 GHz)
  • To use MQTT or Home Assistant, you need to have Wi-Fi enabled
  • A CO2 Gadget meter offers more features than most commercial meters, whilst costing several times as much

| I can’t see any changes after configuring | You haven’t saved | Go to Save Preferences in the menu or wait for the next cycle | | The website looks strange | Browser cache | Clear your cache or use an incognito window |

Important notes

  • Wi-Fi can be switched on or off without restarting the meter, via the menu or the website
  • In LOW_POWER mode, Wi-Fi connects only every N wake cycles (configurable) to save battery life
  • If you’re using MQTT, you need to have Wi-Fi switched on
  • CO2 Gadget supports 2.4 GHz networks (the ESP32 does not support 5 GHz)

Do you also check the Menu Guide. Any questions? Ask on the Telegram group or open a issue on GitHub.

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