Protocol comparison

Fashion Star Servo Communication Method Comparison

1. Model Naming

2. UART Serial Port Servo

Communication method: UART serial port

UART communication usually uses two data wires: TX (transmit) and RX (receive). When connecting devices, the TX of one device should be connected to the RX of the other device, and vice versa.

When Fashion Star servo products are used, the UC-01 adapter board converts standard UART full-duplex communication (separate TX and RX) into half-duplex communication. In other words, the TX and RX signals are combined into a single S signal wire, allowing transmission and reception to share one line and simplifying wiring.

Protocol: proprietary protocol

Detailed explanation: bus servo Communication Protocol - Fashion Star Wiki

Packet structure

1. Command packet

2. Response packet

Functions: single-turn angle control, multi-turn angle control, damping mode, synchronous command control, asynchronous command control, data monitoring, and more. It supports feedback for angle, temperature, voltage, current, power, and status, enabling closed-loop control.
Application scenarios: research experiments, education projects, robot joint control, medical equipment, drones, and short-distance systems that require precise control and data monitoring.

3. RS485 Bus Servo

Communication method: RS485

RS485 uses differential signal transmission. Two signal wires, A and B, transmit data together. The receiving end determines the logic state based on the voltage difference between A and B:

When A voltage > B voltage, it indicates logic "1" (high level).
When B voltage > A voltage, it indicates logic "1" (high level).

This method has the following advantages:

Strong anti-interference capability: During long-distance transmission, signals can attenuate and be affected by noise. Because external interference usually affects both A and B wires at the same time (common-mode interference), the receiving end only cares about the voltage difference between the two wires, so the interference is canceled out.
Long transmission distance: Compared with single-ended signals, differential signals attenuate less. RS485 can usually achieve stable communication over hundreds or even thousands of meters.
Strong common-mode rejection: The receiver can effectively ignore the same voltage changes on both A and B wires (common-mode voltage) and only respond to the voltage difference. This capability is called common-mode rejection (CMRR).

Protocol: proprietary protocol (consistent with the UART low-level protocol above)

Detailed explanation: bus servo Communication Protocol - Fashion Star Wiki

Functions: single-turn angle control, multi-turn angle control, damping mode, synchronous command control, asynchronous command control, data monitoring, and more. It supports feedback for angle, temperature, voltage, current, power, and status, enabling closed-loop control.
Application scenarios: industrial equipment, research experiments, medical equipment, and systems that require strong anti-interference capability and long-distance control.

4. CAN Bus Servo

Communication method: CAN (supports CANBUS and UAVCAN)
Functions: high real-time performance and strong anti-interference capability; feedback for angle, temperature, voltage, current, power, and status
Application scenarios: drones, autonomous driving platforms, AGVs, and mobile robots that require high-speed and reliable communication

5. PWM Servo

Communication method: standard PWM pulse-width signal

The control signal of the servo is a 20 ms pulse-width modulation (PWM) signal. The pulse width ranges from 0.5 ms to 2.5 ms, corresponding to horn positions from 0° to 180°. When a specific PWM signal is provided, the servo rotates to the corresponding angle.

Functions: standard PWM control. Protection parameters can be modified through the Fashion Star PWM PC configuration software, providing comprehensive stall, temperature, and voltage protection. Users can also customize multiple professional parameters through the programmer. Data feedback is not supported, and closed-loop control is not available.
Application scenarios: education, model aircraft, RC cars and boats, entry-level robotic arms, and cost-sensitive applications that do not require feedback.

6. Distributed Serial Bus Servo

Communication method: proprietary distributed bus

Features: graphical programming and simple operation; traditional programming is not supported
Application scenarios: educational robots, programming education, and the company's proprietary robot platform