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Thread: Dynamixel AX-18As not appearing using U2D2

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    Dynamixel AX-18As not appearing using U2D2

    First post here, so give me some slack.

    I bought the hexapod MK3 with AX-18As to continue a project I started in college, but I haven't been able to get the dynamixels to read.

    I followed the procedure outlined here and gave each one the unique ID 1 thru 18 successfully.

    I uploaded a test sketch to the arboti-x controller and got the servos to move, so I know they work.

    At uni, I was able to control the dynamixels through ROS using a U2D2. Now, with what should be the same setup at home, I cant get it to work.

    I have since been using the ROS manager code I got working on Ubuntu from uni and the Dynamixel Wizard 2.0 on both Ubuntu and Windows 10 to try to scan for the motors, which both worked on the university's hexapod, but none of the servos are even showing up on mine.

    Ive searched online and haven't been able to find a solution, so I'm hoping someone here will have some experience with this. If there are alternative programs any of you have used to read multiple servos, I'd love if you'd share.

  2. #2

    Re: Dynamixel AX-18As not appearing using U2D2

    Hi Hexapod guy.

    Sorry, to hear you are having some issues. I am sort of rusty on some of this.

    Sometimes hard to know exactly what is happening on your setup.

    I also do not have a U2D2 so I may miss a few suggestions. But some of the things I would look at include:

    a) How do you have the servos powered? When you turn on power do the servos all blink?

    b) What software (Dynamixel Wizard 2) are you using and is it up to date? Is it configured to scan for protocol 1 servos?

    c) I would try first hooking up one servo to it and see if it works. If so maybe a leg (3 servos) and see if it sees those and see if you can localize down.

    Sometimes with AX12 servos I would have a servo or two revert back to ID1 and collide with the real ID 1... So in my hexapod code I would avoid using #1 as an ID (make it 19) and if it found at startup that it was missing 1 servo and #1 is found, it would optionally renumber #1 to the missing number.

    Again hard to know what is going on. So I start testing very simply. I also often would run my own test sketches

  3. #3
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    Re: Dynamixel AX-18As not appearing using U2D2

    Thanks for responding!

    a) All of the dynamixels are receiving power. All the servos blink when I turn on power.

    b) the software is up to date, and I set it to scan for all possible combinations of protocols, baud rates, etc.

    c) SUCCESS, I have officially discovered one servo, lol. Tried it on windows, plugging in a different power supply, and scanning, and it did come back with the one servo that was plugged in at the time.

    This is a starting point, so now I will go back and plug in each leg, one by one, seeing if I can isolate a problem servo.

    I'm going to try to keep this thread updated in case someone stumbles upon this in the future and was having the same problem.

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    Re: Dynamixel AX-18As not appearing using U2D2

    Alright, update:
    I plugged the other servos in the chain for the same leg, all scanned fine.

    I then plugged in the connector for the two other legs, both plugged into the Arboti-X controller, and now nothing scans. So it is either: The Arboti-X controller, or one of the servos in the two legs. Testing now...

    I have now been able to identify all 18 of the dynamixels. It turns out the problem was with the Arboti-X microcontroller itself. When anything was plugged into it, nothing would read. It might've been something to do with a program uploaded to it, or maybe it could've been damaged somehow, I cant be sure.

    Either way, I wasn't planning on using that to program the servos, so nothing really too lost.

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