Bus Servo Integration with Mitsubishi FX3U and GX Works2

This guide explains how to integrate Fashion Star bus servos with a Mitsubishi FX3U PLC using GX Works2. It covers UC04 wiring, serial configuration, library import, angle control, and position readback.

1. Wiring Instructions

1.1 Device Wiring Architecture

1.2 UC04 Wiring

2. Program Instructions

2.1 PLC Serial Port Parameter Setup

Data bits: 8
Parity: None
Stop bits: 1
Baud rate: 9600

(Because this PLC model does not support 115200 baud, set servo baud rate to 9600 in the PC configuration software.)

2.2 Serial Data Write (via Function Block Library)

K0 ------ Servo ID
K3600 -- Target angle 360.0°
K3000 -- Reach target in 3000ms (3s)
K100 --- Acceleration time 100ms
K100 --- Deceleration time 100ms

Use function blocks to convert the above data and store it in continuous registers, as shown below: D410, D411, and so on.

2.3 Serial Communication Instruction

Data to send is stored in D410
Number of bytes to send is 20
Response data is stored in D200
Maximum number of response bytes is 7

2.4 Serial Send Request

2.5 Serial Port Reset

Reference for serial setup:

(018) Mitsubishi FX3U PLC Communication with Serial Assistant - Bilibili

2.6 Function Block and Protocol Mapping

Protocol reference for Fashion Star bus servo communication:

https://fashionstar.com.hk/wiki/protocols/servo/uart-rs485/

Using the example above (servo ID 0 rotates to 360° in 3000ms), use MOV instructions to store high and low bytes into D410 in order; same rule applies to subsequent registers.