Using the Arduino as a FTDI module

I very new at Arduino, but have some experience with the Raspberry. Im using a Arduino Uno R3.

I am trying to put new firmware on a Sonoff ( and I have seen all the Youtube-stuff on how to do this.

However, I cant seem to get past a Sync-error, when uploading the firmware to the Sonoff.

I have tried switching Rx and Tx - no luck I have made sure that the powersuply for the Sonof gives off 3.3V The Sonoff is flash-mode.

Somewhere it was suggested that I had to remove the chip from the Arduino - tried that - still getting the Sync-error.

The program Im uploading is the blink program as demonstrated in the video here. Links are in the comments:

In the video, he uses a FTDI module, but as the Uno R3 dont have a USBport and it is stated in several forums, that you can use the Arduino directly for flashing, I wanted to give it a try.

If anyone can help me get this Sonoff flashed by pointing me in the right direction, that would be great.


I having also sync issue. I have a FTDI module but I get the following :

Arduino: 1.6.12 (Windows 10), Board: "Generic ESP8266 Module, 80 MHz, 40MHz, DIO, 115200, 1M (64K SPIFFS), ck, Disabled, None"
Sketch uses 222,205 bytes (23%) of program storage space. Maximum is 958,448 bytes.
Global variables use 31,572 bytes (38%) of dynamic memory, leaving 50,348 bytes for local variables. Maximum is 81,920 bytes.
warning: espcomm_sync failed
error: espcomm_open failed
error: espcomm_upload_mem failed
error: espcomm_upload_mem failed

Did you find a solution ? Why do you think that the Son-off is in flash mode ? (I see that it normally is blinking, but after pressing the GPIO0 button and reconnect the power is does not blink)

Eddy The Netherlands

It took some time to solve it for ESP12E devices, but it was in the end the order in which the GND and Power needed to be connected.

My order now :

1) Connected to GND to GPI0 2) Disconnect the USB cable (power is lost) 3) Connect USB cable 4) Upload the sketch

Because it took too long before I solved it, I used ESPEasy for the sonoff devices and flash them directly