GPIO Read speed on the M4 using gpiomon

Hi, I’m having issues reading the GPIO ports (I’m trying with pins 3 and 42). It seems that I’m only able to get coherent raise and fall events when I use them at slower speeds (20 or 30 milliseconds between each change).

This speed seems too slow, I should be able to get correct input using an interval of less than 1ms, but in that case the events I get from the PIN signal change don’t make sense.

Did anyone try to use the GPIO at that speed? I’m running one of the raspbian distributions and trying gpiomon and also trying with custom c# code.

thanks! Federico.