Hello @tlfong01, thanks you for your great research :-) Looking at your oscilloscope output, it does not resemble to any of the message that I have in the documentation. My initial conclusion is that the protocol explained is either wrong or has been significantly changed. It would be interesting to have more samples of communication to reverse-engineer the protocol. The on of your picture is probably about querying the temperature/voltage or position.

Ah, I see. But I am not surprised, because I am using the Win10 Bus Servo Terminal GUI command to turn the motor non stop so I can easily us a scope to display something. There are other things that cause trouble: (1) I am using BusLink version 2.6, but I read the AliExpress and Amazon are selling old versions. So there might be outdated commands. The other thing is that I found HiWonder keeps saying that they cannot help users to develop software, because HiWonder is asking LeWanSoul to develop the LeWanSoul simplex uart servo protocol. So LeWanSoul might not the have motor turning commands.

Ah, supper time, so see you late this evening or tomorrow. Cheers.

In your circuit, I suggest you to add the pull-up resistor and also some 0.5k in-serie resistor between the bus and the servo. This will avoid any error to burn to quickly your devices.

Ah that is a good advice I carelessly forgot . I usually use 330R or 470R series resistor to limit the motor current. I am also using a very small 220VAc to 12VDC 1A (yes, 1A only) PSU then step down to LM2596 12V to 5V to supply the LX-224. So I think LX-224 should at most take 1A or a bit more, hopefully no to fry anything. And also that is why I am using the less expensive servo, not the most expensive one, just in case, ... Cheers

I created this room (chat.stackexchange.com/rooms/112557/lx-224hv-uart-interface‌​) so we don't load this Q&A page too much with unrelated/unfinished content. At the end we can add the working result here just for future users.

update 2020sep03hkt1155

Now I am assenbing a TXS0102 for experimenting with the LX-224HV simplex circuit. I actually have a couple of already assembled TXS/TXB01 02/03/06/08 in hand, but I want a semi permanent test bench version to keep a record.

As usual, comments are counter suggestions are always welcome, especially before I fry something. Ah, you remind me one good thing about chatting in the chat room is that I can easy insert pictures.