How to start, stop and read values ​​from the system timer on Arduino?

Question

Arduino

Hello. There was a problem.
In general, there are 2 sensors, let's say an IR sensor.
And there is a task. Starting the timing at a high signal level on sensor 1 and stopping at a high signal level on sensor 2.
And one more task. If the signal level on one sensor is high, start the timer, if the signal level is high again (after a low one), stop the timer.
How to implement it correctly? Tell me please!
Sat dealt with timer interrupts, with this I more or less understood something. But I don’t understand how I can start the timer by interrupt or something like that.

Answer 1

You don't need timer interrupts, but external interrupts and the millis() or micros() function. Here is almost exactly your case: Arduino Chronograph

Answer 2

You need to get two interrupts:
The first interrupt should be generated on the rising signal from sensor 1 (rising edge)
The second interrupt should be generated on the falling signal from sensor 2 (falling edge)
The first interrupt handler should issue a command to start the timer, and the second interrupt handler should to stop the timer.