Gonna vaguepost so I don’t self dox too much. Had to replace a dead appliance this week. Got a lightly used replacement, no choice about which. It had a wifi spot build in. It would talk to any phone with the mfg app. No auth other than having the app installed! WTF.
You couldn’t disable that! Well not thru the panel controls. Web says you can do it with the phone app. IF you make an account with the mfg for your appliance first. Rofl!
Maybe this approach will help others. What I did was, searched the schematics online. Most appliances, you can find it. Searching model number + schematic often works. There are sites that catalog them.
Using the schematic, I found a connector that powered the wifi. Unplugged that. Re-powered appliance. Confirmed wifi was gone.
My neighbors are not gonna hijack my appliance over wifi, so I wasn’t worried about that. I guess it could find an open WAP and phone home. TBH it was mostly the principle of the thing tho! I don’t want ANY n/w on my appliances, thank you. Ya know?
It’s a tiny skirmish in the war against IOT. Editing here to quote Aragorn, who famously said about IOT, “There may come a day when my appliances connect to the internet. But it is not THIS day!”
First, find VCC and GND. Verify peak voltages with an oscilloscope on the signal wires. Connect all wires, do some stuff in the app while you record.
Most software has analysis functions, if not, check the usual protocols.
If you have more then 5V on the wire, it may be Modbus or other industrial connection standards.
If found the correct protocol, baudrate and so on, I use for example esp32s to sniff in the wire and do a more useful long time capture