Hi,   my current project is about using a NanoPI M1 as a controller for a 3D printer. As such, one wants to have very tight timing on the GPIO output, with as little jitter as possible, to get smooth motion of the stepper motors.   However, it is common belief that getting a fast timing with little jitter is virtually impossible to do under linux, without the help of a dedicated chip just for the IO. While that is true in general on stock kernels, it's possible to vastly improve on that fron