FluidNC laser/CNC controller board

This board is mainly an IO board allowing:

- to control 3 stepper motors (see later)
- to detect 3 independant home switches
- to apply PWM to the laser controller (see later)
- to detect interlock door switches
- to drive 4x220V relays for air assist, vacuum pump, water cooling and light
- to read 3 more inputs

It is controlled by FluidNC / GRBL firmware

It's part of an open source open hardware project to retrofit an old Trotec laser engraver

Project is here : https://hackaday.io/project/193893-retrofitting-an-old-laser-engraver

PCB can be found on PCBWay shared projects : https://www.pcbway.com/project/shareproject/FluidNC_laser_controller_board_70101fd4.html