CNC Shield Board: 1, CNC Shield version 3.0 for Ardu ino. 2, compatible with GRBL 0.9. (Open source firmware running on Ardu ino's U NO that converts G code commands into step signals) 3. PWM spindle and direction pins 4,4 axis support (X, Y, Z, A - X, Y, Z or using pins D12 and D13 Complete 4th axis using custom firmware) 5,2 end stops per axis (6 total) 6, coolant enabled 7, using removable A4988 or DRV8825 is compatible with stepper driver 8. Jumpers set the microstepping of the stepper driver. (Some drivers such as the DRV8825 can perform micro-stepping up to 1/32) 9. Compact design. 10. The stepper motor can be connected with a 4-pin molex connector or soldered in place. 11. The operating voltage is 12-36V DC. (Currently only the DRV8825 driver can handle voltages up to 36V, so please consider the operating voltage when powering the board.) 12. Please note that this is an unassembled kit and requires basic soldering skills. A4988 stepper motor driver: 1. The A4988 stepper motor driver board is a breakout board for the Allegro A4988 DMOS microstepper driver. It has converter and overcurrent protection functions; please read the A4988 data sheet carefully before using this product. Low RDS (On) output2, automatic current decay mode detection/selection3, mixed with slow current decay mode4, synchronous rectification for low power consumption5, internal UVLO6, cross current for protection7, 3.3 and 5 V compatible Logic power supply 8, thermal shutdown circuit 9, ground fault protection 10, load short circuit protection 11, five selectable step modes: full, 1/2, 1/4, 1/8 and 1/16 Ardu ino's U NO R3 Board: MCU: ATmega328USB interface: ATmega16U2 Working voltage: 5V Digital I/O pins: 14 (6 of them with PWM function) Analog input pins: 6 II/O pins Output current: Maximum 40mA3.3V output current : Max 150mA Flash memory: 32kB (including 0.5kB used by bootloader) Static RAM (SRAM): 2kBEEPROM: 1kB Clock speed: 16MHz Packing list 4 X 17HS4401S4 X A4988 driver