Some serial controlled servo motors, like the Waveshare ST3215 and Waveshare ST3025 use magnetic encoders (instead of potentiometers) to determine position. Magnetic encoders should greatly enhance reliability. In my experience with a project called Santa's Shop, servo motors fail after 100 to 200 hours of operation--almost always due to worn potentiometers. I wrote this review to assist users in controlling these serial servo motors using an Arduino Uno because I couldn't find any clear guidance for their operation.The Arduino uses two pins for serial communication, receive and transmit (pins 0 and 1). The serial servo uses one pin for both receive and transmit. Something has to give. A serial bus driver board (around ten dollars) receives the input from the Arduino and does the electrical magic necessary to talk to the servo motor.To connect the Arduino to the bus driver board, pin 0 of the Arduino goes to "receive" on the bus driver board. Pin 1 of the Arduino Uno goes to "transmit" on the bus driver board. Ground on the Arduino goes to ground on the bus driver board. The bus driver board is powered by a 12 volt, 2 amp power supply.Step 1: SoftwareSoftwareThere's a lot of information on the Waveshare wiki, but it's confusing and some of the code just doesn't seem to work.First, we need to load a "library" into our Arduino programming system. In the position where we write a sketch, select "Sketch" (third from left) and click. Select "Include library," then "Manage libraries." In the box under "Library Manager," type "waveshare" and press the Enter key. Scroll down to "SCServo by FT &ws." Click "install."We're ready to go. To control a servo (servo with ID number one, the factory default), try the code below:#include SMS_STS st;#define S_RXD 0//Serial receive pins#define S_TXD 1//Serial transmit piinsvoid setup() {Serial.begin(1000000,SERIAL_8N1);//Initializes serial port 1 communication for controlling the serial bus servo's; SERIAL_8N1 is the configuration data, parity, and stop bits; specifies the serial port pins//Serial1.begin(1000000, SERIAL_8N1);//Set the serial port parameter of the SCServo object to Serial1, indicating that the 1000000 serial port is used to control the servost.pSerial = &Serial;delay(1000);}void loop(){st.WritePosEx(1, 4095, 3400, 50); //Set the position, speed and acceleration of servo 1 with a delay of 2sdelay(2000);st.WritePosEx(1, 2000, 1500, 50); //Set the position, speed and acceleration of servo 1 with a delay of 2sdelay(2000);st.WritePosEx(1, 700, 1500, 50); //Set the position, speed and acceleration of servo 1 with a delay of 2sdelay(5000);}Step 2: Changing Servo IDUsing the same wiring setup as before, the code below will change the servo ID Number from "1" to "9."VERY IMPORTANT: Because this code executes one time--before starting a loop that does nothing--I find it necessary to do the following. Connect the servo to the bus board and power it up. Connect the bus board to the Arduino. Power the Arduino. PRESS THE RESET BUTTON ON THE ARDUINO (it's next to the usb connector).I hope this helps someone use these servo motors.#include SMS_STS st;int ID_ChangeFrom = 1; // Change the original servo ID, and the factory default is 1int ID_Changeto = 9; // new IDvoid setup(){Serial.begin(1000000,SERIAL_8N1);st.pSerial = &Serial;while(!Serial) {}st.unLockEprom(1); //Unlock EPROM-SAFEst.writeByte(1, SMS_STS_ID, 9);//Change IDst.LockEprom(9); // EPROM-SAFE is locked}void loop(){}

Decent servos, documentation leads a little to be desired but you can message support. Python library has some errors and stuff from their previous series of servos, so if you’re not familiar with programming I wouldn’t recommend this. If you are, just keep it in mind and you can debug and work around it. Python lib is also missing a few functions the C++ lib has, but you can write them yourself easily.The speed and acceleration functions are very handy, you can tune these pretty well for whatever you need.