Overview

The Sonoff Dual R2 offers control of 2 relays on one board. 

Flashing

This device uses the ESP8285 module which is different than the other SONOFF products. 

As always, you need to access the serial interface. The four serial pins (VCC, Rx, Tx, GND) are available at the short end of the PCB and can be seen on the left of the image above.

Entering Programming Mode

As with all ESP8266/ESP8285 modules pulling GPIO0 to GND is needed to put the chip in programming mode. You need to connect GPIO0 (button 0) and GND during power up.

Luckily both GND and GPIO0 (as BUTTON 0) are available on the second header. A simple jumper between GND and BUTTON 0 while programming will do the trick.

Flashing from the Arduino IDE

Reference