[Reference thread] Yes, it's flashy but what does it mean? (gShield LEDs)

Here is some information to help those bringing up their X-carve for the first time.

The blue LED on the gShield indicates when the motor voltage is present on the power input terminals of the gShield. LED on = motor voltage present. LED off = no motor voltage present.

Each stepper motor driver IC on the gShield supplies power for two coils within the bipolar stepper motor. The voltage applied to each coil can be reversed by the stepper motor driver. So, take the black/green coil, for example. In normal operation, sometimes the black wire has a positive voltage and the green wire is at “ground”. At other times the black wire is at “ground” and the green wire is at the positive voltage.

There is one green LED for each of the stepper motor driver ICs. The green LED is hooked up in parallel with one of the coils of the motor. So, depending on the “direction” of the voltage appled to that coil the green LED will be on or off.

So, in normal operation you can have the green LEDs in the on state, the off state, or flashing depending on the voltage applied to one of the coils of each stepper motor.