Dynamixel AX-12A compatibility

Official Hardware UNO Family UNO R4 WiFi
1

I was gifted a used AX-12A and after trying to search and read through threads I was wondering how well it could work with an R4 WiFi directly connected and controlled by a single wire, essentially replacing a PWM controlled servo?

Can the R4 WiFi do single wire half duplex serial UART?

If so, is there a simple Dynamixel library for positioning an AX-12A?

Not really familiar with either topic and just want to be sure it’s possible to work before taking on the challenge.

Based on the comments I can find it sounds like the R4 WiFi isn’t ideal for this.

Thanks

2

I have not tried them in a long time.

There are details of some of the stuff I did back then:
Robotis Dynamixel Shield code does not compile - Classic / UNO R4 Minima - Arduino Forum
I believe Robotis maybe put hack in around the issue of LED_RED defined, if not
the hack is shown in either the thread above or the links in it.

There are/were issues with the UNO R4 software implementation of the hardware Serial ports, like there is no TX buffering and the like, that I had a PR to rework a lot of it. I believe others have as well, but not sure if any changes have been incorporated.

3

Thank you for the feedback @KurtE

My desired goal would be to replicate Dynamixel Library With No Additional Hardware requiring only a single Uno R4 WiFi pin for position control of the AX-12A as a direct replacement for a PWM servo.

But the Single Wire Serial library (which I believe is based off of the Software Serial library) does not show as being compatible with the UNO R4's.

And by searching, I cannot find any reference to anyone trying to implement single wire serial on an R4 WiFi or Minima.

Do you think it is possible?

I assume getting single wire serial to work on an R4 would be the first step.

And if that works, then getting a Dynamixel library to work, although for my project, to start I only need to simply tell the AX-12A to move to a position.

I really appreciate that you helped identify and fix the RED_LED issue.

4

Yes, that would be possible. The correct search term would be "half duplex serial" and naturally requires two wires, counting ground.

5

Thank you @jremington
For "half duplex serial" to work, software serial needs to function on the R4 correct?

I can find threads talking about software serial NOT working and fixes which I believe are based on @KurtE's hard work, but it doesn't look like they have been implemented by Arduino yet...or is software serial working reliably on the R4?

I don't mind trying to implement fixes manually, but it isn't something I am well familiar with.

Then should I make my own fork of Single Wire Serial for the R4 WiFi?

Just trying to make sure I understand the proper steps in order.

Thanks

6

If it is not possible to use a UART (SCI module in the RA4M1) in half duplex mode, another option is "bit bang" an I/O pin, AKA software serial.

The latter is not so trivial with an advanced processor like the RA4M1, and neither is reading the processor data sheet. If you insist on using the R4 WiFi, you probably have a significant challenge either way.