Discussion between tlfong01 and Adrian Maire

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5:10 AM

Yes, I saw that you explained each byes of my bus link rotate motor screen capture. But I don't understand why my "Rotate Motor" string becomes your "Read Voltage Input Request"?

2 hours later…

Adrian Maire

6:53 AM

>But I don't understand why my "Rotate Motor" string becomes your "Read Voltage Input Request"?

IMO, When you use the software (Hiwonder windows UI), it request periodically temperature/voltage/position to the servo, to display them in the screen. The "rotate" directive is probably sent before.

Te more clear: I think that out of the many communications that happens between the servo and Hiwonder software, you made zoom on the one which request voltage input.

1 hour later…

tlfong01

8:13 AM

Ah, yes, actually that is what I have just done before I saw your message. (1) I did also suspect the Bus Servo Terminal does repeatedly request Vin, Temp, Pos. In other words, there is no need to rotate the motor in order to display waveform on the scope. (2) So this time I set to servo mode, and adjust position to around 735 and watching the scope.

(3) I found scope shows repeated waveforms every 350 ms, roughly in two parts. (4) I always find it difficult to read the bits and bytes, perhaps you can help out and translate the bits into bytes.

Notes - (a) I did try to change Vin from 6V to 8V and found no change in the amplitude of the 5V UART waveform, so I guess Vin is solely for powering the motor, and has nothing to do with the UART stuff. (b) I also guess, the BusLinker is for LX-16A which is not HV and only work to 7.2V. But the servo LX-824HV should work to 11.1V, so I increase Vin to 10.0V and found every body happy to work as usual, for at least about 15 minutes without any smoke coming out.

Now about the 10bit command string. I guess the initial "10-" before the "0x55 0x55" string is just to "wake up" the servo, and is not part of the command string, which only starts with 0x55, 0x55. So If I am going to use a terminal emulator, or later a python program, I can forget the "10-" part and just start a commend with 0x55, 0x55. I have not yet decided not to do next. Comments and suggestions welcome.

Please also feel free to ask me to try other things you like. Ah, jogging time. See you late this evening or tomorrow. Cheers.

Adrian Maire

8:54 AM

I am currently at work, so I will translate the screenshots later.
Thank you very much for testing 8V and 10V and confirming that the UART signal is always 5V. With this, I can discard the issue of voltage and try others ideas.
Considering the "10": it is nothing about the servo itself, but about UART protocol in general. Reading a bit more about the subject: UART send a "0" before each bytes and a "1" after each byte (so we see the "10" between them). This is used to synchronize clocks in the serial communication. you don't need to add them to the string, it is automatically done by the UA…

6 hours later…

tlfong01

3:07 PM

Now I have set up and tested the following hardware and software to prepare testing sending commands to servo to request temperature.

(1) Set up PC Win10 USB to UART adapter baud rate 115200bd.

(2) Setup Win10 RealTerm and test loopback (hex) numbers

(3) Setup TXS0104 3V3 to 5V0 logical level shifter.

(4) Test loop back with 5V0 TxD shorted to RxD