Flashing Itead Sonoff devices via original OTA mechanism!!! WORKING!!!
After a lot of search, I could find this excellent project to change the firmware to this switch lx-wifi-03o without soldering nothing !!! I changed the firmware to 3 of my devices today and they are work ing perfect.
This is a script to update a Sonoff device from the stock firmware to Sonoff-Tasmota purely over WiFi.
The last model of PCB board of the switch lx-wifi-03o is not possible to soldering cables to the wifi module, so, it is the only way to upgrade the firmware.