Fastest Way for ESP's to directly communicate "Alive" to another ESP after boot

Using Arduino Project Guidance
1

Hi guys

What is the fastest way of an ESP informing another ESP that he's got power / is on? I basically need to trigger an I/O if the Master ESP is powered on. Multiple ESP's might be triggered by the Master ESP when powered on. The goal is to have as little delay as possible and no internet should be needed. They are close to each other.

Thanks

2

spongioblast:
The goal is to have as little delay as possible and no internet should be needed. They are close to each other.
Thanks

Via an I\O pin that one ESP sets and the other reads.

3

My bad, by close I meant they can reach each other but there cannot be a physical connection. Basically I'm wondering if its possible to track an alive beacon that the slave esp's listen to. The main reason for this is that I can't create a network with the master as the master esp is powered on and off, where as the slave ones always have power.

The project idea is to have the master esp connected to the main light switch, which turns on other lights in the room that are plugged into a normal socket and an esp between them.

4

Reads like you have many “Masters” and just one “Slave”.

So you want the “many” to respond to the “one” when it gets turned on.

You could transmit a ultrasonic pulse that the many are listening for.
You could transmit a infrared pulse that the many are looking for.
You could create a WiFi host that the many will search for.

5

If you don't want to use WiFi then the ESP-NOW feature may be appropriate.

...R

6

Awesome, ESP-NOW was exactly what I was looking for! Thanks!