Sonoff DUALR3 Switch Module
Model reference: 6920075775402
Sonoff DUALR3

Available from:


Flashed with:
Serial port

Template for ESP32 device
{"NAME":"Sonoff Dual R3","GPIO":[32,0,0,0,0,0,0,0,0,576,225,0,0,0,0,0,0,0,0,0,0,7296,7328,224,0,0,0,0,160,161,0,0,0,0,0,0],"FLAG":0,"BASE":1}
Download a tasmota32 binary to flash. Flashing instructions.

by blakadder

Opening the Case

Press the case to release the clips. My case was not glued at all but some might be. After opening it, the PCB will simply pop out.


Serial Flashing

Disconnect the device from mains power! Like for real!

The four needed pins (3V3, RX, TX and GND) are available at the back of the PCB and can be easily identified.


Connect them to the serial-to-USB adapter. If you have alligator clips or some ingenuity you can do it without soldering, notice that ground is connected to any ground pin on the board, not the marked pad necessarily.

Look Ma, no soldering!

To enter flash mode you need to connect GPIO0 to GND. Luckily Sonoff decided to give you a practical button that does just that.


Download tasmota32.bin (you need v9.3.1.2 and above) or tasmota32-bluetooth.bin if you plan on using the Bluetooth gateway feature.

ESP Flasher

For easiest flash use ESP Flasher. Launch ESP Flasher, select the port for your serial-to-USB adapter and your binary, make sure DUALR3 is in flash mode by pressing down the on board button then connect your serial-to-USB adapter. Finally click “Flash ESP” and wait until complete.


Using command line esptool.py you need to download all the additional required files (**do not right click to download them but click each link and download using the “Download” icon).

Flash using this command line:

esptool.py --chip esp32 --port COM5 --baud 921600 --before default_reset --after hard_reset write_flash -z --flash_mode dout --flash_freq 40m --flash_size detect 0x1000 bootloader_dout_40m.bin 0x8000 partitions.bin 0xe000 boot_app0.bin 0x10000 tasmota32.bin


After the flash is complete you will have to connect the DUALR3 to mains and configure Tasmota with webUI using the Wi-Fi AP. ESP32 usually cannot boot properly with power supplied by the serial-to-USB adapter!

Apply the template and make sure “Module 0” is selected. If the power readings are off, perform power monitoring calibration.

Zero Cross Detection Support

To enable Zero Cross Detection use this template

{"NAME":"Sonoff Dual R3 (ZCD)","GPIO":[32,0,0,0,7552,0,0,0,0,576,225,0,0,0,0,0,0,0,0,0,0,7296,7328,224,0,0,0,0,160,161,0,0,0,0,0,0],"FLAG":0,"BASE":1}

GitHub discussion

Flashing instructions by NotEnoughTech

Comparison with Shelly 2.5