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I am trying to drive 2 stepper motors using A4988 motordrivers and I am using the following circuit diagram as shown in the image enter image description here

Only change from the above circuit diagram is that I have not connected the grounds of the motor driver and controller together(common ground). The controller am using is an RPi 2B. I have connected only the STEP, DIR and stepping mode pins to the Rpi.

I have fried one Rpi previously using the same connections but I could not find the exact reason for this behaviour.

I need to know whether there is a chance of back current from the motor driver through the STEP and DIR pin.

Won't the motor driver be able to protect the controller from the same? Should I connect the ground pins together?

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    \$\begingroup\$ You must connect the grounds! Without that there is no common reference for signalling. \$\endgroup\$ – Chris Stratton Dec 24 '18 at 6:15
  • \$\begingroup\$ Thank you for the reply. I got advised that I should connect a diode between the Rpi ground and driver ground to prevent back current from the motor driver to Rpi. Is there a chance of back current via the motor ground? I do not want to fry another raspberry \$\endgroup\$ – AK46 Dec 24 '18 at 7:12
  • \$\begingroup\$ A diode will not work. Again, you must connect the grounds. \$\endgroup\$ – Chris Stratton Dec 24 '18 at 13:01
  • \$\begingroup\$ Thank you.I figured that out the mistake in that. I got the circuit working. \$\endgroup\$ – AK46 Dec 26 '18 at 5:13

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