I'm trying to create a cape that will safely power my BeagleBone Black from my car's electrical system. The design I am using is based on the one from this answer. The circuit there suggests a simple voltage divider to connect the ignition switch to a GPIO on the Raspberry Pi, which could then detect when the car is turned off.
I believe this should work for the BeagleBone Black as well, except the documentation says very clearly that "NO PINS ARE TO BE DRIVEN UNTIL AFTER THE SYS_RESET LINE GOES HIGH." (p. 95)
Now, I'm relatively new to electronics. I'm doing my best to research, so please bear with me if I'm way off on this.
I did some searching, an it seems what I need is a tri-state buffer to feed the ignition signal through. Am I right about that? And would something like the NL17SZ126 be the best tool for the job? Or should I be doing something completely different?