I created a project with 1 stepper motor with two microcontroller the arduino and nodeMCU both has different code to control the stepper, arduino for system lock password using keypad while the nodeMCU control stepper via blynk. The problem is if i power on both arduino and nodeMCU, and use either one of them the other one is not functioning or rather no power. How to fix it to control freely the stepper without any issue. Sorry for the grammar.

I tried everything i could but always the same problem