2018-03-24 23:22 GMT+01:00 Lyndon Nerenberg <lyn...@orthanc.ca>: > By far the easiest way to do this is to connect a switch to the door that > opens/closes as the door opens/closes. This assumes that when you say "the > door moves" you really meant "is opened or closed". > > Whether the switch is normally open or normally closed doesn't matter. Wire > the switch to a serial port; connect one side to DTR, the other to CD.
Serial ports are long gone on todays laptops sadly. > Now you can write a program that runs a loop that (1) opens the blocking tty > device, then (2) reads the descriptor, which will block until CD drops > returning an error from read(2), at which point you close the descriptor and > repeat the loop. A method I implemented in the past at our hackerspace was to use an ethernet nic, and some kind of modified loopback cable. Wire 1(tx+) to 3(rx+) and a switch or a photoresistor between 2(tx-) and 6(rx-). When the switch closes the loopback is completed and the link goes up. ifstated(8) detects it and runs whatever you want. Send a mail, logger(1) to a remote syslog, snmp trap... You can even use a cheap managed switch and very cheaply add plenty of ports for on/off sensors. The switch sends a trap when a link goes up/down and there you go. Kudos to the project that gave me this idea: http://www.newtonnet.co.uk/catfeeder/ :)
