I am trying to hook up my SuperPID to an Arduino Uno running GRBL V1.1. The problem I'm having is how to hook up the "Run" connection on the SuperPID. It is supposed triggered by the Spindle Enable pin on the Arduino pin 13. However even after uploading GRBL to the Arduino, the pin 13 led light flashes on the board which in turn causes the SuperPID to constantly turn the "Run" on and off. I have looked into the GRBL config.h files and already enabled VARIABLE_SPINDLE for the PWM signal. I also enabled USE_SPINDLE_DIR_ENABLE_PIN. I am still having trouble getting this to work. Has anyone else had any luck? Thanks.