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Dynamixel interfacing -- offerings and discussion
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Please be positive and constructive with your questions and comments.

Dynamixel interfacing -- offerings and discussion

by scottferg on Fri Oct 16, 2020 2:15 am

I noted with interest that in the New Products 10/7/2020 video Adafruit announced carrying Dynamixel AX-12A servos in the store. I'm not sure if the current "out of stock" state is a result of customer demand or if they're just not stocked yet. But these servos are pretty cool, albeit expensive, and I suspect this introduction might spark new interest, especially in those who'd not heard of them before. The video and the product page do gloss over the inconvenience of the half-duplex serial interface required to get the most out of these devices. The circuit/adapter required to achieve half-duplex functionality from the serial ports provided by devices like Arduino and Feather processors is not complex but may be a hindrance to many users.

I began working with Dynamixels in 2008; developing software libraries and designing and working with hardware interfaces. I thought this might be a good opportunity to share what I’ve learned and what I’ve made and to initiate the flow of help and information between those with experience and those looking to get started with Dynamixels. For anyone interested, I offer my design/implementation for a simple Dynamixel AX-12 interface driver board, generalized Arduino library and a summarizing document. It’s way too much to put here, so you can find all this at my website, along with a link to a gallery of images at: http://www.forestmoon.com/Software/DynamixelIO/

The document there includes a survey of some of the more interesting interfaces (boards and shields) that I’ve discovered recently. One is a very simple design, similar to mine, that is available (ready to use) for a reasonable price. I’ve ordered a few and will report back, if there’s interest here. This may be a very helpful device for Adafruit to put in the store as well!!

ALSO… If you’re interested in driving a network of Dynamixels from a PC, you can find another project on my website (http://www.forestmoon.com/Software/) to drive an AX-12 Arm (including C# libraries) and another utility to explore Dynamixel functionality that could be quite useful even if you’re ultimately targeting a microprocessor. While you’re there, you might also check out my GearDXF program and Fusion 360 plugin, FM Gears, for 3D gear design. It’s all free! (I’m not selling anything or sponsored by anyone.)

Enjoy!

scottferg
 
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Re: Dynamixel interfacing -- offerings and discussion

by adafruit_support_bill on Fri Oct 16, 2020 6:29 am

Thanks for sharing your work with these servos. I will forward this to our products team.

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Re: Dynamixel interfacing -- offerings and discussion

by adafruit2 on Fri Oct 16, 2020 12:24 pm

thanks, added link to product page

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Re: Dynamixel interfacing -- offerings and discussion

by scottferg on Mon Dec 21, 2020 8:22 pm

If anyone is interested, I did try out the Dynamixel Interface Board V2 I alluded to before and mentioned in my document. It is a quality board and works as advertised. I tested it using a Feather 32u4 and my Dynamixel library. I connected the board's 5v input to USB power while connected to a PC via USB. It also worked with the 5v input connected to the Feather's 3v line, even though the Dynamixel is spec'd for 5v data comms, so I'm not sure that's a robust expectation. I'd recommend this board as a simple and compact interface solution if your not up to my DIY implementation.

Pros: A quality product and quite inexpensive at only $8!
Cons: It took 40+ days to get the board shipped from the maker in Mexico.

If someone (like Adafruit!) were to buy these in quantity, or make them in the USA, and offer more responsive shipping, this would be a great option for makers. (BTW: I don't know the seller and don't benefit in any way from expressing my opinion here!)

You can find the product at:
https://www.tindie.com/products/savagee ... -board-v2/

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Re: Dynamixel interfacing -- offerings and discussion

by scottferg on Mon Dec 21, 2020 8:26 pm

To be clear: like virtually all Dynamixel interfaces, this one actually powers the servos with a separate line that just passes right across the board to the motor and requires a higher voltage. The 5v input on the board is just for data.

Enjoy!

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Re: Dynamixel interfacing -- offerings and discussion

by adafruit_support_bill on Mon Dec 21, 2020 9:06 pm

Thanks for posting that. I will let our products team know about it.

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Please be positive and constructive with your questions and comments.