All of the tools that I found on the FAQ page or in forum posts for re-flashing didn’t work for me.
You need a Serial to USB converter, which are very cheap. It needs to have a 5v option. Most can switch between 5v and 3.3v.
You also need some DuPont wires to make the connections.
On the OpenGarage there are 6 holes (iirc), of which you use 4. You use GND, 5v, Rx, and TX. Rx goes to Tx on your adapter.
Hold the button on the OG while plugging in the USB and it’ll be in flashing mode.
On my computer (I have Linux) I installed esptool from the software center. On Windows or Mac you can research how to install esptool.py.
Download og_1.1.0.bin from the OpenGarage “compiled” folder on GitHub.
I used the command:
esptool.py –port /dev/ttyUSB0 write_flash 0x00000 og_1.1.0.bin
You might just need “esptool” instead of “esptool.py”, and you might need to use “sudo” in front to get out permission to the USB.
If you want more help with flashing these chips, searching for “how to flash Sonoff” will bring up lots of info and videos, which are similar to the OpenGarage.