@tlfong01 (1) I really want to do the assignment you give me so i can understand step by step and more details, but i have no USB to serial cable in my home, the cable is only available in the lab on my campus and i'm out of town now, so i'll do it later when i'm back.

(2) Meanwhile, i try to reconfigure my AX12A with joint mode [here's the picture](https://imgur.com/fCyjAxd), i just click the set default button and click the joint mode. After that i really copy all the script from [oppedijk](http://www.oppedijk.com/robotics/control-dynamixel-with-raspberrypi), look like [this](https://imgur.com/HCHlcrR), then i running this program, and [here](https://www68.zippyshare.com/v/EtZfaRl6/file.html) is the result video.

I was very surprised that it was moving, that's what i expected from the start when i followed the tutorial above, but it won't moving if i'm using wheel mode, so i think the problem is in my instruction packet, but i've checked and counted it many many many many times :(