For my project I want to read the individual alarms from 11 smoke detectors, so I need 11 GPIO inputs, which is more than Wemos D1 offers. Therefore I tried the Pro Mini Extender: I flashed an Arduino Pro Mini with the appropriate software, connected everything as written in the wiki, defined D5 as ...

Thanks a lot for your help, integrating the diodes solved the problem, I didn't even need a level converter. Now I can start wiring all smoke sensors

Thanks for the fast reply! I also tried other pins, without success.
I know level converters, but can you please explain how I can split the signal using diodes?

Thanks in advance!

Best regards,
David

Hey there! I wanted to build a fire alarm system for my house using wired EI650C smoke detectors. Those smoke detectors have two wires; if one detects smoke, it gives 5v on the wires. In addition, if you put 3-5v on the wires, the smoke detector gives an alarm. So you should be able to either read t...