I am trying to build a low-latency timing application. Basically, I want to build a sensor that works to time a 100 meter dash for a bunch of high-schoolers. So the individual should try to cross the starting line laser and then the first microcontroller should send data to another sensor at the end to start the timing which ends when the user crosses the laser at the second line.
Which network protocol would make sense for this? I have no issues building a laser circuit to start the timing but I'm more concerned with how to get the second signal (at the finish line) to start the timing with low latency to get the times accurate. I considered the lora protocol but I have no data with respect to how much latency (milliseconds) to expect.
With radio, you can never count on high speed, 100% reliable communications, especially when using consumer grade radio modules over distances approaching 100 meters.
For your application, 100 meters of wire will work just fine, and would be a simple, easy to implement, extremely reliable approach.
I would agree with @jremington, very difficult to ensure with RF that the timing packet is received, it could easily be missed. You would likely need several RX and TX RF devices in parallel to ensure that the timing packet was reliably received.
A bit of wire does seem a lot easier ....................
We used to build such timers commercially for a customer. They used a microphone to hear the starting pistol as the beginning time for the race. Then the optical beam break for the end of the race.