Asked — Edited

Servo Ports Not Working

ez-b v4 ports D2, D4, and D12 do not work. All of the servos work if plugged into different ports but are unresponsive when plugged into those ports.

Upon initial assembly following all of the "LEARN" courseware for our brand new Revolution:JD ezrobot up through lesson 4: "Connecting to JD over WiFi" we discovered 3 servos were not able to be moved using the controls in the "Server Fine Tune Profile" window. Specifically the left shoulder rotation, upper left arm bend and left hip bend servos (connected to D2, D4, and D12 respectively). Continuing on with the lesson, we attempted to use the prepared wave command as directed in the 6th minute of the video. Our robot did not wave as shown at time 7:00 in the video. On further investigation we discovered the 3 joints that could not be moved in the "Server Fine Tune Profile" process could not be actuated by any of the prepared move commands, while all other servos moved as expected.

To trouble shoot, (specifically to see if the servos were bad) we reentered the "Server Fine Tune Profile" window and then switched the wires for ports D2 and D3. Upon switching, the left shoulder could now rotate and the right could not, demonstrating both servos were functional and port D2 was not functional. A similar process was used to determine that all servos are functional but ports D2, D4, and D12 are not functional. Is there anything I can do to fix this? Or do I need to replace the ex-b v4 piece? And if so, how do I go about doing that?

Further trouble shooting steps already taken include:

  1. Recycling the power
  2. Ensuring full battery charge
  3. Disassembling and reassembling JD (again following along with the third lesson "Building JD Humanoid" as we did initially, and both times there were no steps missed or incorrectly performed)

Thank you very much for your assistance in this.

Sincerely, Phil


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Sorry, none of those links were relevant to the problem I am facing.


Correction, it is D3, not D2 that is not functioning.


Thanks for providing details. Have you verified the wires are matching the colors? And indeed connecting all three pins? Please watch this video to notice the BLACK wire matches the BLACK side of the ezb connector.


Thank you so much for getting back to me.

Yes, I definitely did. You're tutorial video was very clear about that. We were always certain to have the black wire on the correct side for all connections.



I've never heard of a port or two not functioning before :). We can have your ezb replaced. Contact Us for warranty and quote this thread link.

Ports can be damaged if they are shorted to each other with a screwdriver or bent - doesn't sound like this was the case.

We'll get you up and running in no time :)


Thank you so much! That was definitely not the case, all the pins look fine and we were very careful throughout the assembly. Your lessons and tutorials are awesome and we are very excited to continue with you guys.


Just a comment DJ but I almost made the mistake of installing my servos backward. Industry standard connections for servos always have the signal wire pointing inboard or towards the device label. At least in the RC world where all these servos originate from. I instinctively hooked mine up this way as I have all my life but made a quick second check before powering it up and found the mistake.


Time to revive this question.

What do you do if you have a port that WAS working, but then it's suddenly NOT working?



What do you do if you have a port that WAS working, but then it's suddenly NOT working?
Before assuming the port is not working, i would try first to confirm the diagnose, reset the controller, reconfigure, keep a minimal functional setup i.e. good battery, controller and a functional servo, connect the servo to the port, and then you can use EZB web page to test the digital ports (move all servos).

If the port is damaged, but the other ports and the controller in general is still good, ignore the damaged port. If you are experiencing other problems maybe is time to replace the controller.

From a configuration perspective there's nothing you can do to "recover" a damaged port.

From hardware's perspective the labor cost to diagnose the fault component and to fix i.e. desoldering, soldering and the replacement part is higher versus buying a new controller.


Ya, I found a bad port on one of my EZB's. I had plenty of other good open ports so I just moved the cable. However I can see how this could be a problem with a fully loaded EZB with no available ports. PTP's correct. time to get another EZB. No need to by a whole new EZ-B if you only need a couple new ports. Just get an IoTiny for a lot less money (if you have room in your robot for it) for the extra ports and add it to your project.


Just to add a little to this, it is fairly easy to kill a port.  I accidentally shorted one when the EZB was on (power to signal I think.  It was the tip of a screwdriver that got too close to the open port) and it never worked again, but the rest of the EZ-B was fine, so I just stuck a servo plug with the wires cut off and a label that said BAD so I would remember not to try to use it.



Woops! damm screwdrivers. lOL.

I love the blank plug idea with the label. Gotta remember that the next time I get careless with my short circuit equipment.