PulseIn function

Hey everyone,

I have a project with a LM555 timer and need to calculate how much time it takes for an input to go from LOW to HIGH and then to LOW again.

Basically, I want to know the period of a square wave generated by the LM555 timer.

I did it with Arduino using the function Pulseln. But I need to do this using a Beaglebone and programming in C++ (Using QtCreator).

Is there a way to "open" the function PulseIn so I know what it does? Moreover, do you guys have any piece of code that might help me?

Thank you in advance.

This seems rather off-topic for the LinuxCNC forums.
But:
The Arduino code is here:
github.com/arduino/Arduino/blob/master/h...wiring_pulse.cpp#L30

But I doubt that it will really translate easily to BBB as I anticipate it uses a hardware timer in the microprocessor.

What time resolution do you need?

I can imagine ways to do this with LinuxCNC HAL, but it's a rather heavyweight package just to measure a pulse.
(Unless you are already using LinuxCNC and this timing needs to be done in a LinuxCNC context)

Andypugh, thank you for the answer.

I need a resolution of about a few microseconds.

I have tried translating the code from arduino to C++ but as you said, it uses many of other arduino "built-in" functions.

You might be able to do it with the Beaglebone PRU, but I think that the only expertise with that is on the Machinekit project. You could try asking there?

Thank you all for the great answers. I believe that the best way will be through PRU. But I was thinking, what if I used PWM reading libraries (black lib for example) on this square wave?

Any thoughts?

I really think you are asking in the wrong place, to be honest.

Yeah, maybe.

Thank you anyway Andypugh