Tapping into a stepper motor driver signal without degrading it?

Hi Everyone!

I have a 3d printer with a ramps + mega setup. I’d like to be able to measure the speed of the extruder motor microstepping with a 2nd Arduino. To do this, I’m thinking of tapping into the step pin on the motor driver (pololu a4988) and wiring it directly to one of the input pins on the 2nd Arduino. From there, the 2nd Arduino will measure the frequency of pulses, and adjust an LED to be brighter when accelerating and dimmer when slowing down.

Here’s my problem: I don’t know if I can simply tap into the signal without degrading the stepper motor signal. Is there a proper way to do this without degrading the signal?

In short: How do I tap a signal without degrading it?

Thanks so much everyone! :)

There is plenty of fan-out on Arduino output pins, start to worry if you want to drive a dozen logic loads, or very long cables, but not for two or three local loads. Use a common ground.

So just hook it up? Nice, I like that answer :)

Thanks Mark!

Suggest you use a 4k7 resistor in series just in case there are any glitches.