Installation

Flash S0tool firmware directly from your browser. Requires Chrome or Edge and a USB cable.

Before you start: Install USB drivers for your Wemos D1 mini. See Troubleshooting if your device is not detected.

Step-by-step

  1. Select the configuration matching your hardware below.
  2. Connect your Wemos D1 mini via USB to your PC.
  3. Click Connect — select the USB serial port.
  4. Choose Install S0tool, then click Install.
  5. If it fails, hold the boot button on the device and try again.
  6. After flashing, connect to your 2.4 GHz Wi-Fi network.
Done! Home Assistant will auto-discover the S0tool under Settings → Devices & Services.

Standard Configurations

Standard
Standard

Watermeter (NPN) + kWh (50-100ms)

Watermeter
Watermeter only

NPN sensor only

kWh
kWh Meter only

S0 pulse input (50-100ms)

Connect to Home Assistant

Option 1 — During installation

After Wi-Fi setup the installer offers a direct link to add the device to Home Assistant.

Option 2 — Auto Discovery

S0tool appears automatically under Settings → Devices & Services if on the same network.

No Chrome or Edge? Manual Wi‑Fi Setup

The browser installer above needs Web Serial support (Chrome, Edge, or Opera on desktop). If you're on Firefox, Safari, or a mobile browser, flash the firmware once via the ESPHome dashboard in Home Assistant instead, then set up Wi‑Fi manually:

  1. Power on the S0tool. On first boot (or after a factory reset) it starts its own Wi‑Fi access point named S0tool.
  2. On your phone or laptop, connect to that S0tool Wi‑Fi network.
  3. Open a browser and go to 192.168.4.1.
  4. Enter your home Wi‑Fi (2.4 GHz) network name and password.
  5. The device restarts and joins your network — Home Assistant will then auto-discover it as above.
Tip: This same captive portal reappears any time the device can't reach the configured Wi‑Fi network, so it's also a quick way to move the S0tool onto a different network later.