Wiring connection

[Laroto]

How are you connecting the servo(s) to the rpi? Directly to the serial pins or are you using Hiwonder's control board?

[Escain]

Hi @Jaroto and welcome!

Short answer:
You need the Hiwonder control board, or some equivalent electronic.

Long answer:
Hiwonder servos uses 5V half-duplex UART, while Raspberry-pi uses 3.3V full-duplex (on GPIO).
Even with some simple 3.3V to 5V electronic in the middle, I don't think that the full-duplex to half-duplex can be managed by software (Real-time on a Raspberry-pi are over several ms of jitter, while here, we need 0.1ms or less. If I remember correctly).

I hope this helps :-)
Adrian

[Laroto]

I also have the controller board (https://www.hiwonder.com/products/serial-bus-servo-controller).
The idea is to use a powerful computer (or a raspberry pi) to run an application and send commands to the servos.
Did you test connecting the board to the computer and the servos to the board and send commands through it?

[Escain]

I got this one: https://www.hiwonder.com/products/hiwonder-ttl-usb-debugging-board

So I got several servos connected to the board, and the board connected to the raspberry-pi (through a level switcher 3.3V to 5V).
Then, you can use my library in a software running on the RPI. You could potentially drive it through ssh or similar.

Notes:
The copper-like board is just a power supply.
5 to 3.3V is made just two resistors (divisor)
3.3V to 5V is done with a NXP 74HC126N or similar.

Cables ( I think, but to be checked):
yellow: seems the board power.
white: 5V power
black/blue: gnd
red: RPI-RX
orange: RPI-TX
Dark-violet: board-TX
light-violet: board-RX

VID_20200910_192248.mp4

[Laroto]

That was what I wanted to see! Thank you. I will use a LiPo battery as a power supply. I will first try to communicate with USB, otherwise I will do that setup with the voltage divider (for data only). I did not know serial was open drain.

[Laroto]

One more not related question: what screws did you use to mount the servos? I am referring to those brass looking screws

[Escain]

Those are just (M1.5 or M2) brass insert nuts: plastic screws can not be mounted and unmounted many times, consequently, I inserted those inserts with a solder-iron. And, obviously the corresponding screws.

[Laroto]

I was aware of the inserts in the 3D printed part. Just not sure about the tiny holes for the servo. I bought a ton of M2 but I think these are too big. I'll try M1.5