My application is that I'm trying to create a very small, "button battery" powered device to sense the opening and closing of a switch and send state changes via WiFi to another device on the network. I will be using an ESP8266 (ESP-03) which has a reset (RST) pin and a deep sleep mode.
To my understanding, the deep sleep mode can be initiated by software. Then the RST pin on the ESP needs to be brought low for at least 100us (but preferably less than 0.1 sec) to wake it up. At that time it can check one of the GPIO inputs to see if the switch is open (high) or closed (low) and then put it back to sleep until the next open/close event.
To clarify by example, one application would be to send a notification each time a box is opened or closed, which needs to include the current status. For instance, it sits closed on a shelf. When someone opens it the ESP wakes up, sends an "is open" signal, and then goes back to sleep. When the box is closed it wakes up again, sends an "is closed" signal and goes back to sleep. The box may be open or closed for a long time, so we only want the reset pulse signal sent when the state changes.
I've seen some other articles that talk about similar situations but there don't appear to be any "this worked" comments or the cases are slightly different. The monostable flip flop looks promising (http://www.bowdenshobbycircuits.info/page9.htm), but am I understanding it correctly? Also, will it drain the battery?
I'm trying to keep this device as small and energy efficient as possible.