Apparently you measure between 12V and signal. You should measure between signal and GND. Signal low means a maximum of 1.5V, signal high means at least 3V. Voltages should never exceed 5V.
Measuring pins not connected makes no sense. They pick up electromagnetic radiation and have arbitrary values.
Looking at the measurements (7V = 12V - 5V), your wiring apparently has indeed a short, so it's a wiring, not a firmware problem.
Measuring pins not connected makes no sense. They pick up electromagnetic radiation and have arbitrary values.
Looking at the measurements (7V = 12V - 5V), your wiring apparently has indeed a short, so it's a wiring, not a firmware problem.