UCP messages and how to use UCP

Relative Coordinate XYZ Message Format and Absoulte Coordinate XYZ Message Format have parameters X, Y, and Z. There is no way to send a command to the fourth servo. How do I control the fourth servo?

There is no way to read the servo angles from the uArm. How do I find out the actual servo positions?

What host software uses UCP? Does the ROS program for uArm use UCP?

Hi @cuteboy , are you using uArm Metal or uArm Swift or Swift Pro?