Thanks, in general the jrk 21v3 driver has a good performance vs price rate.
Nevertheless I encountered as a good improve opportunity or firmware update the possibility to command target and maximal speed. Cheap servos as the Dynamixel can do it, I do not understand why the so versatile and general purpose JRK is not able to do it. By the way, it is not well documented how and which parameters in addition to the target, could be changed through serial commands. The given workaround by dear Mr. Derrill seems to work but it requires additional programming and an artificial loop introducing other problems like undesired transients signals. I guess that the parameters table of the driver could not be changed (as that of Dynamixel) on the fly and so it requires to burn data by configuration (as a kind of static parameters) Is it?