Default GPIO PIN state after boot

[MarkHaysHarris777]

hi Artyom, whether any SBC will be a suitable controller depends on the characteristics of the control circuit, electrical dynamics and other things like security ( and others ).

Let's say you want to build a control circuit for your garage door that will automatically recognize just your car but no others. You have a radio chip on the windshield of your vehicle which can be 'read' from the eve of your house. cool. But here is the problem: what happens if your place has a power spike, or the power drops and later restarts. What happens to the door ? You don't want the door opening by itself on POR ( that would be a security problem ) and you don't want the controller to 'hang' on a power glitch either ( or else you can't get back in either ).

I have actually known people to build the above with an Arduino or a Raspberry PI, and all of them had to deal with this issue. Multi-level design is usually required ( or some fancy buffering like Pete was talking about ) becuase usually the I|O pins cannot be relied upon to maintain steady state during POR. Also, usually a good UPS is required too, so that power glitches don't afffect or shutdown or hang the system once started.

I believe you can build a reliable control system with the Pine ( I'm researching that the whole time I have had mine ) as long as you take POR into account, and have a good UPS or other system to handle power outages. BUT your system must not rely on any steady state during POR regardless of SBC; although, the RPi is ( in this instance ) may be more reliable in that situation. ( I'm just trying to be complete here )