[dcb]

It's a little complicated.

Main issue is that the injector is a one or a zero to the software. a "solid" one with the current design is going from 12 to zero volts. The hold "one" is going from 12 to 11 or so, not 12 to 0.

And the CPU measures in reference to ground, so 11 volts might as well be 12 (or 14 if the alternator is turning). So we want something that can turn a threshold amount of current (or voltage drop across the injector) into a solid one or zero for the CPU, and it has to be simple as possible/inexpensive/durable.

There are ways to measure voltage in analog in software but it is significantly slower than the digital inputs and would be a large bit of coding and a little bit of rewiring.

Basically we are looking for something simple (optoisolator and resistors maybe) that will turn any floating voltage drop across the injector above say 1 volt, into 3-5 volts and anything below into 2-0r zero volts (or vice versa, the software can invert it now).