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Thread: Bad luck with Dynamixels?

  1. Bad luck with Dynamixels?

    After toasting my ArbotiX, I think I've done in my USB2Dynamixel, too! Lol. I think robots hate me.

    Everything was working fine. I was connecting, writing and reading to the servos via the U2D on my Mac as well as on a Ubuntu box. But after trying to get it to work with an Edison, the U2D now seems not to be working properly. It shows up as a device, and I can connect to it just fine, but there doesn't seem to be any data transiting to or from the servos. Dynamixel Wizard connects fine, but can't find any servo I plug in. The Firmware Recovery utility can't find them either. Again, these were working fine before the Edison entered the fray. I have tried updating my FTDI drivers in Windows. I was running 2.08.28, which I read should have been fine, but since the U2D wasn't responding, I tried updating to 2.10 without any luck. I checked the vendor and product IDs on the U2D and they are correct. I've tried swapping out the power hub I was using for an SMPT2Dynamixel.

    I've been lurking around these forums looking for any information I can find about the U2D. Could trying to connect the U2D to the Edison possibly have killed it? Is there a way to restore the factory settings? Or should I just accept the possibility that my U2D is bjorked because of its run-in with Edison?

    My ArbotiX replacement should be landing today, and I've ordered a USB2AX from Seeedstudio (it's on backorder, unfortunately), but it would be nice to know what I'm doing wrong that my controllers seem to be dropping out of the sky like flies. Am I not powering things correctly? I switched to using a 10A brick or a 4500mA/35C/3S via my now defunct ArbotiX-M when I was driving 18 servos (I think I'll run current through the power hub rather than through the Arbotix regulator from now on), but I'm using a 2.5A all wart when testing single servos. And besides, isn't the power pin on the U2D unconnected anyway? So any power issues wouldn't blow back on it, right?

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    Re: Bad luck with Dynamixels?

    Is the switch selecting the correct comms method? Does it work on any of your machines with any of the servos?

    USB2Dynamixels tend to be pretty durable, except for the USB connector breaking off the PCB. I think there have been a few people that managed to kill the TTL buffers, but not sure how simply using it with an Edison could cause that. I've had problems where connecting a wall-wart servo power supply to the U2D after it was plugged into the PC triggers a USB device re-enumeration because of the sudden change in ground voltage, and it might be possible that a similar, but more severe, event may have caused damage to the TTL buffers (not seeming very likely, but may be possible). May just have been random ESD frying something.
    Please pardon the pedantry... and the profanity... and the convoluted speech pattern...
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  3. Re: Bad luck with Dynamixels?

    Quote Originally Posted by tician View Post
    Is the switch selecting the correct comms method? Does it work on any of your machines with any of the servos?
    I did hit it into the wrong position by accident a couple of times while testing. Would that cause damage? I did ensure it was in TTL mode for this round of testing.

    Quote Originally Posted by tician View Post
    ... kill the TTL buffers, but not sure how simply using it with an Edison could cause that.
    Dunno, I was just thinking that in my attempts to try to power the Edison via the OTG port while simultaneously having the U2D plugged in could have done it. I have an Lshapped OTG adapter that provides a female USB-A jack as well as a female mini OTG pass-through that is intended to allow the Edison to power peripherals when in host mode. However, I thought I could power the Edison through this port, but after doing some reading, I've come to the conclusion that the very act of applying power to that port probably disabled the OTG host mode anyways. Whether it somehow also did something to the U2D is a separate question.

    Quote Originally Posted by tician View Post
    I've had problems where connecting a wall-wart servo power supply to the U2D after it was plugged into the PC triggers a USB device re-enumeration because of the sudden change in ground voltage, and it might be possible that a similar, but more severe, event may have caused damage to the TTL buffers (not seeming very likely, but may be possible).
    Hmmm, so the conventional wisdom is to plug in the power BEFORE plugging in the U2D to the computer? I guess I can see how it might affect the logic of the circuit, although I can't believe it would actually do physical damage.

    Quote Originally Posted by tician View Post
    May just have been random ESD frying something.
    Hmmm, I did leave it plugged in over night. Maybe my cat brushed up against it.

  4. #4

    Re: Bad luck with Dynamixels?

    I think robots hate me.
    You're not alone! We will all be first against the wall when the robot revolution comes.

    Regarding the USB2Dynamixel, I use a USB extension pigtail (just 6") to not have all of that weight hanging out the USB port.
    If the Edison is already a usb2go host adapter, you probably already have that cable setup. If not, it's worth the few dollars for the protection!

  5. Re: Bad luck with Dynamixels?

    Quote Originally Posted by jwatte View Post
    You're not alone! We will all be first against the wall when the robot revolution comes.

    Regarding the USB2Dynamixel, I use a USB extension pigtail (just 6") to not have all of that weight hanging out the USB port.
    If the Edison is already a usb2go host adapter, you probably already have that cable setup. If not, it's worth the few dollars for the protection!
    Thanks for the heads up. I guess I'll have to invest in another U2D at some point. I'm hoping that the U2AX will be shipping soon, but I don't know if I should hold my breath. I wish there was more demand for it so it would better justify Xevel's efforts.

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