Add Robotis sensors to U2D2 controlled XM540-270R system . .

Hi Folks,

I’m driving a XM540-270R off of a Pi5 via U2D2 in a linear actuator application. I need to incorporate travel limits switches or at least a “home” position switch into the design (thinking either MGSS-10 or TS-10) and would love to be able to just daisy-chain them in to the RS485 bus.

To do that, it looks like I need either adapters such as the OpenRB-150 and logic-level shifter, or I need an entirely different controller - but I can’t quite tell which.

Can someone please point me in the right direction?


If it was me, I would leave that U2D2 alone to drive the DXL, and find some kind of 3.3V magnetic sensors that work through the GPIO Port of the Pi 5. There is no need for going to OpenRB-150 or logic-shifter.

The RPi Forum would be the place to check for this kind of info.

Our 540 size servos actually feature a built in external accessory port specifically for this use case. With this you shouldn’t need to add anything extra in order to add an analog or digital limit switch to the RS485 bus.

Hi Jonathon,

That looks like what I am looking for. Will the Robotis accessory switches such as the TS-10 work here?

Also, for a given external port how do I detect a switch event for that servo in the Wizard or via an API?



It should work with the TS-10, although it would likely be easier to wire in a simple two wire limit switch.

The state of the switch can be read using the external port data registers in the DYNAMIXEL’s control table.