Universal Robots+

C12A0 Unknown Message Error

Hi everybody,

Today I upgraded my robot’s software. The UR motherboard was changed from CB 3.0 to 3.1, and Polyscope was also upgraded from 3.4.1 to 3.4.5.

If my custom URcap is not installed everything runs fine.
If my custom URcap is installed an error message appears at seemingly random moments.

This is Polyscope’s log:

Any ideas?

Hello Jubeira

Update to Polyscope 3.4.5 requires manual update of your Safety Control Board. please refer Release note


You can contact local distributor or UR office for same fro support


Just to be clear: it is not required to update SCB, software is backwards compatible. I’d recommend contacting tech support providing fault report along with script generated by urcap.
EDIT: Can you also share SCB firmware version here?

Thanks for your replies!

Here’s a screenshot with version information:

Note that it’s not necessary to create nor run any robot program for the fault to happen. This occurs just by having the URCap installed with this CB / Polyscope version.

There is something terribly wrong or you’re running in simulation mode.
Controller can’t even determine SCB version. If this is running on real robot, then please ask regional tech support to update SCB.

Actually, the error here is the C12A0 Unknown Message Error.
The C192A18 is essentially the other safety processor acknowledging that the first one is in fault state.

The C12A0 fault state is triggered, if the Safety Processor intercepts messages that are invalid.
The Safety Processors are located on the eth0 interface of the motherboard, while the eth1 interface is the “open” port for communication to external devices.
If possible, please refrain from accessing the eth0 interface, as this may trigger this fault condition.

Firmware update of the SCB is not necessary, while updating to PolyScope 3.4.5 - PolyScope is backwards compatible with earlier firmware on the SCB.
However since the SCB firmware cannot be updated automatically, not updating the SCB firmware means that the release notes related to SCB firmware will not take effect.

From SW 3.2 and the corresponding firmware release, the safety processors started transmitting their firmware version. When the About screen above states that the URSafetyA and URSafetyB firmware versions are “Older than” respectively 470 and 209, this means that the firmware on the SCB is pre-3.2.
If you do not have any issues with the robot, nor desire to use some of the new added safety features later than 3.1, the system can perform OK with this pre-3.2 firmware release.

1 Like

Thanks for the reply!
There is a background task that may be using that interface in some cases; for now we dropped that feature but in the future we will go back to it, so this information is very valuable.
I will come back to this thread when I can confirm that this was the root cause of the problem.