I have an easy circuit wired up, with an LED connected to pin 18 on the BOARD reference. I run a simple program to put pin 18 to HIGH, which turns the LED on, and then a couple of seconds later, I set pin 18 to LOW, and finally I end my program with GPIO.cleanup().
At this point the LED is off, which means that pin 18 is off (LOW). Now I reboot or restart my Raspberry Pi, and when it boots back up, the LED on pin 18 turns on again, even though the pin was off before I rebooted the Raspberry Pi.
Why may this be happening? How can I configure a specific pin, like pin 18 to be off when the Raspberry Pi boots up? And I don't want any GPIO pins to be on HIGH when the Raspberry Pi boots up.
I am concerned about this problem, because let's say that pin 18 is connected to a DC motor on a robot, and when the Raspberry Pi boots up, the motor will turn on, and this is not something that I want because that will interferes with the whole structure of the robot, and some motors might start and others won't, depending on the pins they are connected to. I want to manually turn on all the motors in a synchronized manner.
One other thing is that not all the pins have this problem. Some stay off when the Raspberry Pi boots, but others don't.