The pin high is probably 12v DC
so I know I will have to buck convert them to 3.3v.
What pins are available on the Wemos D1 R2 to connect the UPS alarm pins to? And do I only have to test if these pins go high?
The UPS data sheet is not specific on what a high digital signal is (in volts).
Opto-isolators only seem to be used for noisy signals.
As far as I can research some, if not, most of the digital pins have an intrinsic function attached to them.
D2 and D1 are the SDA (serial data) and SLC (serial clock) of the I2C bus.
Furthermore, I assume I connect alarm signal return to the GND pin?
http://dcpower.eaton.com/Customer-Premises-info.aspbut no alarm line specsEaton does not reply to emails (holidays?)
Primary pin selection by me:GndGpio12Gpio13Gpio14Gpio04Comments?
Researched opto-isolators, but only had real success when searched for opto-couplers.
There are no hi to lo modules available so it looks like I'll have to build my own on a protoshield.
Most optocouplers (if not all) use an input low voltage to output a high voltage. I want to go the opposite way (12 or 5v to 3.3v).
So I have to reduce the power supply voltage of 12v DC to 5v,The output resistors are just pullup resistors and can be 10kΏ. The 4N35 has a forward current of 50ma...