I use custom marlin firmware for muve3d. I try use d4,5,6,11 pin with M42 to control relay but nothing happen. I had check with voltage meter but nothing. Anyone can help me diagnostic
Try using M43 to verify those pins. With M43 you have two options, you can ground a pin and see if it sees a state change (and if so it will report it). Also, you can tell it to toggle pins within a range and some rate. You can watch if the pins are toggling.
