Context. I am using an ESP32 and a small circuit to control an electronic lock on my one of my exterior doors. It is powered by batteries. It has a door magnet sensor to detect when the door is open or closed and this launches an interrupt which wakes the ESP32 and allows it to transmit information (have tried both push and pull, e.g. server / client, both can be made to work). I want to have another interrupt that I can send wirelessly from something which is plugged into power.
False positives (waking the device when it doesn't need to be) are acceptable. False negatives are not so hot but tolerable if something like repeating the signal a few times results in it working.
Things I have considered. Buying an ultra low power bluetooth solution and using that microcontroller to wake the esp32. I dislike this one the most because it adds the most cost and complexity. I have to program something like the QN908x.
Finding out if there is a way to do this with RF without all the overhead of bluetooth and complicated protocols.
Use something like an IR emitter and receiver.
Provide power directly to the IC and control the battery powered circuit which controls the motor using something like Resonant Inductive Coupling or even LEDs (I can place these things withen 2-3cm of each other). This latter option being the most interesting and relevant to this forum but also might be the least feasible. The circuit would need to communicate state back and forth. I could use something like a very simple FPGA or some low power IC that can store 4 different possible states. Opening, Closing, Straining and doing nothing.
Before I start designing I wonder if anyone has solved this problem. Namely trying to make something that can communicate wirelessly and consumes less than 5ma. It would not have to check for transmissions more than once every 2-3 seconds. Some latency is ok.