[Little Rookie]

Good catch! You are correct that the input have been reversed in the Phill Rogers design he calls v3.5.

However, to comply with the Speeduino board connections, IC1 (8-pin) VR- input is on pin1, and should connect with MAX9926 IN1- (pin 15). This is how the v3.x versions by @noisymime were configured, as in your v3.1 schematic.

Would it still work the other way? Without thinking too much, probably, though settings would be reversed from expected, with various consequences similar to using reversed-polarity sensor wiring.

Perfect, my head was starting to panic, I didn’t know which one to follow. I'm going to try to make my board with the V3 version schematic.

Thank you!