@ DJ I ordered the OpenRB-150 which uses the Wizard 2.0 software but won't be here to end of next week so can't adjust anything yet in the servos.

All the servos we are talking about here are factory default, NIB.

I re-ran the Dynamixel XL-330-M077-T and it does the same thing. I guess I was missing something?! If I get 350 deg of motion on 4095 steps I can control the degrees in the servo set up between 1-180.

This behaves so different than my Dynamixel MX-64s that are in Alan, so it was confusing me on their new behavior/operation?!

Hi fxrtst,

Your observations are very insightful and help underline the nuances with these servos. Let’s break down what’s happening:

1. Fixed Internal Resolution on XL430W250 Mode
   When set to XL430W250 mode, the servos are designed to operate with an internal resolution of 4096 steps. This internal resolution directly affects the physical movement of the servo horn (in your case, about 350 total travel). Even if you try to change the max position value in ARC’s Dynamixel plug-in, the servo’s firmware (stored in EEPROM) will override that setting and revert it to 4096.

2. Effect on Motion Range

   • When the servo is using 4096 steps, you get the full travel of roughly 350.
   • Forcing a lower value (like 1024) through the plugin might appear to limit the movement (resulting in about 90), but because the plugin resets it back to 4096, the servo continues to use its full internal setting.
   • You can still control the motion on a per-command basis by mapping the degrees in your ARC configuration (for example, mapping 1-180 within your control commands), but the underlying hardware resolution remains fixed.

3. Differences with Other Models (e.g., MX-64)
   Some Dynamixel servo models, like the MX-64, provide a bit more flexibility to adjust or map the degree range (via EEPROM settings or additional mapping in the skill) so that you can effectively choose a custom resolution. With the XL430W250 protocol, the behavior is consistent-its default programming (and EEPROM values) defines the full range, and any attempted override via the ARC plugin isn’t persistent.

4. Next Steps & Your OpenRB-150
   Your plan to use the OpenRB-150 with the Robotis Wizard 2.0 software could indeed provide the additional control you’re looking for. With that setup, you might be able to perform a factory reset or adjust the EEPROM values directly to change the resolution scale if the servo’s firmware supports that. This direct control might allow you to "program" a different range before using them in ARC.

In summary, the "screwy" behavior you’re experiencing isn’t a bug with ARC-it’s largely due to how the servo’s internal firmware and EEPROM are structured for the XL430W250 protocol. The settings for resolution are inherent, and while you can map your commands to a different range in ARC, the servo itself will always revert to its factory default of 4096.

Do you have any other questions about controlling these servos, or would you like to see an example of a JavaScript mapping routine to integrate a custom degree range within your ARC scripts?

Looking forward to your reply!

Feel free to delete this post! All is well...if this is how they are meant to operate.

@Dj and @athena thanks for the help, guidance and clarity. Oh and DJ playing around with servo recorders again and  speed settings for recordings....ill say it again brilliant!

Okay - awesome. But I think we should keep it for historical usage. It’s an important feature to recognize.

these servos are soooo programmable that I don’t even know all the options.

As for saving the value in the robot skill, that should be looked at. I’ll add it to be reviewed.

Hi DJ_Sures,

Great to hear that everything’s working well on your end!

Your point about keeping the current behavior for historical usage is well taken. These servos are indeed very programmable, and the various options available can sometimes be a bit overwhelming. It’s important to preserve and review these features so that users understand the breadth of what’s possible, even if the settings in the robot skill appear to revert to a default value.

I’ll make sure to pass your feedback along for review regarding saving the values in the Dynamixel robot skill. It’s discussions like these that help us continuously improve ARC and our overall offering.

Please feel free to reach out if you have any further questions or if there’s anything else you’d like to explore. Thanks again for your input and happy robot tinkering!

Best regards,
Athena