This is my take on a GRBL Mega328 3-axis stepper driver board for my CNC mill. It is designed for the new Trinamic TMC2100 stepper driver chips on a breakout board sold by Watterott-Electronics (which I really like, because they are really cool (they decrease the current when the motor is idle, and they are silent =;) available here link ). But you could also use other stepper-drivers like the Texas Instrument DRV8825 or Pololu A4983 if you like. On the software side I use bCNC as g-code sender and autoleveling platform for milling PCBs. The board and schematics where designed with KiCAD To be on the save side I have added a cooler for the stepper drivers. It uses a printed duct and a 40mm 5V fan. Aug-29-2015 uploaded newest sketchup file, with a easier to print fan-duct and a improved bottom and top enclosure parts. I have a few professional made PCB's now (just the bare PCBs, no soldered parts), so if somebody is interested in those, let me know. Update! There was a stupid mistake in the FTDI (USB) section, VCC was connected to 3.3V and that caused the USB connection to fail at random times or completly to fail.I fixed the PCB and schematics.SMD electronics is on the top side, the trinamic drivers are soldered on the backside (easier too cool from this side if needed). There is 5V DCDC converter (aimtec AM2D-0505SZ) module needed for the galvanic decoupling. I ordered mine from www.reichelt.de: http://www.reichelt.de/Wandler-Module-DC-DC/SIM2-0505S-SIL7/3/index.html?ACTION=3&GROUPID=4956&ARTICLE=35055&SEARCH=SIM2-0505&OFFSET=16&WKID=0& The pcb is currently modified for etching and drilling at home, so if you want to send it to a board manufacturer please check the drilling diameters first. I soldered all connectors on the backside because that was the only way to solder them with no through hole plating... Also watch out for the voltage rating of the 47uF capacitors for the stepper drivers, they have to be rated for the power-supply voltage you use (at least 24V but up to 45 Volts). There is a 40 pin Raspberry-Pi connector on board, which supplies 5V and RX/TX connections and my plan is to use a Raspberry Pi with the very cool bCNC software to control my CNC without a seperate PC/ laptop, but I haven't tried that yet though.