Doorlocks of our hackerspace has been RPi controlled almost since the original RPi came out, maybe 2013. Nowadays we got 4 doors on 3 RPIs (internal and external), with over 200 members that has access. Using MQTT to communicate with our membersystem since 2016 or so.
Of course. Our system controls electronic latches in the door frame, while the door-bolt is unmodified - so all doors can be opened from inside without any electronics. Additionally there are separate fire-exits from all our rooms.
