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⚡ Flash Sonoff

Flash relay firmware to your Sonoff TH — no Arduino IDE needed

⚠️ Use Google Chrome or Edge — Web Serial is not supported in Firefox/Safari

📋 BEFORE FLASHING

1

Wire your FTDI/serial adapter

FTDI to Sonoff TH wiring diagram

Connect 3.3V→VCC GND→GND TX→RX RX→TX — use 3.3V only, never 5V!

⚠️ IMPORTANT: The button you need to press is the small button on the Sonoff board itself — NOT any button on your USB serial adapter!
2

Enter flash mode (bootloader)

1) Disconnect the USB adapter from your PC
2) Find the small button on the Sonoff PCB board and hold it down
3) While still holding the button, plug the USB adapter into your PC
4) Keep holding for 2-3 seconds, then release
5) The Sonoff is now in flash mode — no LEDs will blink, that's normal

3

Click the button below

Select your COM port when prompted. Flashing takes about 30 seconds.

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🔧 CONFIGURE VIA USB

After flashing, configure WiFi & relay number directly over USB — no captive portal needed!

Not connected

📱 ALTERNATIVE: CAPTIVE PORTAL

If you prefer, you can also configure via the Sonoff's WiFi hotspot:

1. Unplug USB and replug without holding the button
2. Connect to WiFi: SonoffRelay-Setup (password: 12345678)
3. Open 192.168.4.1 in your browser — enter WiFi & relay settings
4. Hit Save & Connect

💡 To reconfigure later: Hold the Sonoff button for 5 seconds

🔧 DRIVERS & TROUBLESHOOTING

CH340 USB Driver — needed if your serial adapter isn't detected:

📥 Download CH340 Driver (Windows)

Extract the zip → run the installer → replug your USB adapter

Can't get the flash to work? Try the Tasmota Web Flasher as a test:

🔗 Tasmota Web Flasher (test your setup)
Tasmota settings for Sonoff TH:
• Firmware: Tasmota (ESP8266 version, NOT ESP32)
• After flashing Tasmota, configure: Module Type → Sonoff TH
• GPIO12 = Relay, GPIO13 = LED, GPIO0 = Button
• If Tasmota flashes OK, your wiring and driver are correct — come back here and flash our custom firmware