SST Automation SSTCOMM GT100-MQ-RS User manual

Modbus / MQTT Gateway
GT100-MQ-RS
User Manual
V 1.0
SST Automation
E-mail: [email protected]
www.SSTAutomation.com

www.SSTAutomation.com
Important Information
Warning
The data and examples in this manual cannot be copied without authorization. SST Automation reserves the right
to upgrade the product without notifying users.
The product has many applications. The users must make sure that all operations and results are in accordance
with the safety of relevant fields, and the safety includes laws, rules, codes and standards.
Copyright
Copyright © 2023 by SST Automation. All rights reserved.
Trademark
is the registered trade mark of SST Automation.
Technical Support Contact Information
www.sstautomation.com
E-mail: [e-mail]

www.SSTAutomation.com
Catalog
1 Product Overview ......................................................................................................................................................1
1.1 Product Function ............................................................................................................................................ 1
1.2 Product Features ............................................................................................................................................. 2
1.3 Technical Specifications .................................................................................................................................2
1.4 Related Products .............................................................................................................................................3
1.5 Revision History .............................................................................................................................................4
2 Hardware Description ................................................................................................................................................5
2.1 Product Appearance ........................................................................................................................................5
2.2 LED Indicators ............................................................................................................................................... 6
2.3 Configuration Button ......................................................................................................................................6
2.4 Interfaces ........................................................................................................................................................ 7
2.4.1 Power Interface ................................................................................................................................... 7
2.4.2 RS-485 Serial Interface ....................................................................................................................... 7
2.4.3 Ethernet Interface ................................................................................................................................ 9
3 Mounting ................................................................................................................................................................. 10
3.1 Mechanical Dimensions ............................................................................................................................... 10
3.2 Installation Method .......................................................................................................................................11
4 Quick Start Guide ....................................................................................................................................................12
4.1 Hardware Connection ...................................................................................................................................12
4.2 Software Configuration ................................................................................................................................13
5 Software Instructions ...............................................................................................................................................16
5.1 Software Interface Description .................................................................................................................... 16
5.2 MQTT ...........................................................................................................................................................19
5.2.1 Client ................................................................................................................................................. 19
5.2.2 Advanced Config ...............................................................................................................................21
5.2.3 Topic .................................................................................................................................................. 23
5.3 Ethernet .........................................................................................................................................................24
5.4 Subnet ........................................................................................................................................................... 25
5.4.1 Modbus Master Interface Configuration ...........................................................................................27
5.4.2 Modbus Slave Interface Configuration .............................................................................................30
5.5 Tools ............................................................................................................................................................. 31
5.5.1 Upload Config and Download Config .............................................................................................. 32
5.5.2 Confilict Detection ............................................................................................................................ 35
5.5.3 Export Excel ......................................................................................................................................36
5.5.4 Communication Debug ..................................................................................................................... 36
5.5.5 AutoMap ............................................................................................................................................38
5.6 Property Operations ......................................................................................................................................39
5.6.1 Property Configuration ......................................................................................................................39
5.6.2 Name Properties in Order ................................................................................................................. 40
5.6.3 Properties Name Conflict Detection ................................................................................................. 40

www.SSTAutomation.com
6 Working Principle ....................................................................................................................................................41
6.1 Connection Process ...................................................................................................................................... 41
6.2 Data Exchange ..............................................................................................................................................41
Appendix A: MQTT Message Format ....................................................................................................................... 42
A.1 Default Format .............................................................................................................................................42
A.1.1 Publish Message ...............................................................................................................................42
A.1.2 Subscribe Message ........................................................................................................................... 46
A.2 Custom Message Format .............................................................................................................................49

www.SSTAutomation.com
1
1 Product Overview
1.1 Product Function
GT100-MQ-RS is a gateway that can exchange data between Modbus Serial (RTU/ASCII) through RS-485 and a
MQTT Broker through a wired WAN connection. It can connect Modbus RTU/ASCII Master or Slave devices to
the IoT Cloud by MQTT. The wired Ethernet interface supports MQTT connections to various IoT cloud
platforms such as Microsoft Azure IoT, Amazon AWS IoT, Mosquitto and other generic MQTT Brokers.
Note: To connect to AWS or Azure using authentication, you must use a security certificate.

www.SSTAutomation.com
2
1.2 Product Features
One RS-485 Interface - Modbus Master/Slave
As a Modbus Master interface, it can connect field devices to the IoT Cloud Platform by implementing a
data acquisition and device control Ethernet network.
As a Modbus Slave interface, it can integrate a PLC, DCS and other Modbus master stations into an IoT
Cloud Platform Ethernet network.
Ethernet network is always online. Supports connection detect and auto reconnect functions.
Supports MQTT connections through a wired WAN network.
TLS V1.2. Supports custom Client ID.
QoS 0 and 1 supported.
Supports debugging function on both the Modbus and MQTT side.
Supports publishing timestamp and time zone (Configurable Feature).
Supports two publish modes: Publish when data changes or publish periodically at custom cycle time, which
can reduce the data traffic.
Real-time device status monitoring on the IoT Cloud Platform.
Ethernet connection status display.
Applies to industrial fields with high reliability. Supports real-time monitoring and automatic reset.
1.3 Technical Specifications
[1] One serial interface
Physical standard: RS-485.
Parity: Odd, Even, None, Mark, Space.
Stop bits: 1 or 2.
Baud rate: 1200~115200 bps.
Protocol: Modbus RTU/ASCII Master/Slave.
Modbus command: 01, 02, 03, 04, 05, 06, 15, 16.

www.SSTAutomation.com
3
Interface type: 3.81 mm 3-pin port.
Galvanic isolation: 1kV photoelectric isolation.
[2] One Ethernet interface
Physical standard: RJ-45, full-duplex / half-duplex.
Speed: 10/100 Mbps, Auto-Negotiation.
Supports DHCP and Static Configuration.
[3] Maximum data and connections:
Modbus RTU/ASCII:
Input bytes ≤ 512 bytes
Output bytes ≤ 512 bytes
Maximum connections: 31 serial devices
Maximum commands: 100 commands (as Modbus master)
Maximum properties:
Modbus Master-Slave: 1000 properties.
[4] Power: 24 VDC (11~30 VDC),<1W
[5] Operating temperature: -4°F~140°F (-20°C~60°C). Humidity: 5%~95% (non-condensing).
[6] Dimensions (W*H*D): 1.0 in * 4.0 in * 3.6 in (25 mm * 100 mm * 90 mm).
[7] Installation: 1.4 in (35 mm) DIN RAIL.
[8] Protection level: IP20.
1.4 Related Products
Related products include:
IOT600-TWX-TS
GT200-MQ-IE
GT200-MQ-IE
To get more information about related products, please visit SST Automation’s website: www.sstautomation.com.

www.SSTAutomation.com
4
1.5 Revision History
Revision
Date
Chapter
Description
V1.0
2/16/2023
ALL
New release

www.SSTAutomation.com
5
2 Hardware Description
2.1 Product Appearance
Note: This picture is for reference only. The product appearance is subject to the actual product.
Serial Interface
Configuration
Button
Power Interface
Ethernet Interface
LED Indicators

www.SSTAutomation.com
6
2.2 LED Indicators
LED
State
State description
PWR
OFF
The device is not powered on.
Green ON
The device is powered on.
SG
Green ON
MQTT connection succeeded.
Green Blinking
MQTT connection failed.
TX/RX
Red Blinking / OFF
The RS-485 interface is sending / not sending data.
Green Blinking / OFF
The RS-485 interface is receiving / not receiving data.
ENS
Green, slow Blinking
Failed to connect to the Internet.
Green, quick Blinking
Fixed IP Address: 192.168.0.10
Red Blinking
Locating the gateway.
Green ON
Successfully connected to the Internet.
2.3 Configuration Button
The configuration button is located on the bottom of the GT100-MQ-RS. It is used to reset the IP address and to
enable/disable configuration data protection.
To reset the IP address, hold the configuration button for 3 seconds after powering on the GT100-MQ-RS. The IP
address will then be set to 192.168.0.10 and the ENS indicator will quickly blink green. This function can fix the
IP address when the GT100-MQ-RS can’t be searched in normal status. Hold the configuration button for 3
seconds again, and the GT100-MQ-RS will be restarted and begin operating normally.
To toggle configuration data protection, double press the configuration button after powering on the
GT100-MQ-RS to disable uploading/downloading configuration data. The GT100-MQ-RS can be searched but
cannot be configured. This function can be used to prevent unauthorized operations to the device. Press the button
again to set the device back to normal.
Button Action
Description
Hold for 3 Seconds
IP Address Reset:
The IP address is set to 192.168.0.10 and the ENS is blinking green quickly.
Hold the button for 3 seconds again to set the device back to normal.
Press Twice
Configuration Data Protection:
Uploading/downloading configuration data is disabled. The GT100-MQ-RS can
be searched but cannot be configured. Press the button again to set the device
back to normal.

www.SSTAutomation.com
7
2.4 Interfaces
2.4.1 Power Interface
The GT100-MQ-RS gateway uses a 24V DC power supply.
2.4.2 RS-485 Serial Interface
The GT100-MQ-RS has an RS-485 serial interface which uses a 3-pin terminal. Its pinout is defined as follows:
GND
D-
D+
1
2
3
RS-485 Specification:
1. Network topology: Linear bus with active terminal resistors at both sides.
2. Baud rate: 1200 bps ~ 115.2 Kbps.
3. Physical Media: Shielded twisted-pair cable that also can cancel the shielding, depending on environmental
conditions (EMC).
4. Station number: 31 stations per section (without repeater), and up to 127 stations in total (with repeaters).
5. Plug connection: 3-pin terminal.
Pin
Function
1
GND, Power ground
2
NC, Not connected
3
24V+, DC
Pin
Function
1
GND
2
D-, RS-485 Data Negative
3
D+, RS-485 Data Positive
GND
NC
24V+
1
2
3

www.SSTAutomation.com
8
RS-485 Installation:
1. All stations are connected with RS-485 bus.
2. Up to 31 stations can be connected per section.
3. Connect a terminal resistor (120Ω, 1/2W) in parallel at both ends of the communication lines to ensure stable
communication.
Note: There is no internal terminal resistor inside of the GT100-MQ-RS gateway’s RS-485 interface.
GND
D-
D+
1
RS-485 Device 2
RS-485 Device 1
RS-485 Device N
...
GT100-MQ-RS Serial Interface
2
3
120Ω
120Ω
RS-485-
RS-485+
RS-485-
RS-485+
RS-485-
RS-485+

www.SSTAutomation.com
9
2.4.3 Ethernet Interface
The Ethernet interface uses an RJ-45 connector and follows the IEEE 802.3u 100BASE-T standard. Its pinout
(standard Ethernet signal) is defined below:
Pin
Signal description
S1
TXD+, Transmit Data+, Output
S2
TXD-, Transmit Data-, Output
S3
RXD+, Receive Data+, Input
S4
-
S5
-
S6
RXD-, Receive Data-, Input
S7
-
S8
-

www.SSTAutomation.com
10
3 Mounting
3.1 Mechanical Dimensions
Size (width * height * depth):
1.0 in * 4.0 in * 3.6 in (25 mm * 100 mm * 90 mm)

www.SSTAutomation.com
11
3.2 Installation Method
Using 1.4 in (35mm) DIN RAIL.
Install
Uninstall

www.SSTAutomation.com
12
4 Quick Start Guide
4.1 Hardware Connection
1. Connect the power supply to the GT100-MQ-RS as follows.
Note: Please do not power on the devices before finishing and confirming all the connections.
24V+
24V DC Power
GND
NC
24V+
GT100-MQ-IE Power Interface
GND
2. Connect the serial devices to the GT100-MQ-RS. For more details on wiring, see Chapter 2.4.2.
Note: The GT100-MQ-RS doesn’t have a terminal resistor in the RS-485 serial interface. When connecting
multiple RS-485 serial devices, it’s recommended to connect a terminal resistor (120Ω, 1/2W) in parallel at
both ends of the communication lines to ensure stable communication.
3. Connect the GT100-MQ-RS with the PC via Ethernet cable. The GT100-MQ-RS can be connected directly
to the PC or to a network router.
Note: Ensure that the GT100-MQ-RS network segment matches the PC’s network segment.
4. Power on the GT100-MQ-RS.
GND
D-
D+
RS-485 Device 2
RS-485 Device 1
RS-485 Device N
...
GT100-MQ-RS Serial Interface
120Ω
120Ω
RS-485-
RS-485+
RS-485-
RS-485+
RS-485-
RS-485+

www.SSTAutomation.com
13
4.2 Software Configuration
Download, install, and run the configuration software SST-MQT-CFG. For more details, please see Chapter 5.
1. Download the configuration software SST-MQT-CFG from www.sstautomation.com and install it. Open the
software and select the GT100-MQ-RS product.
2. Configure the Client (MQTT Client configuration).

www.SSTAutomation.com
14
3. Add or edit MQTT Topics.
4. Configure the Ethernet and Subnet Interface parameters.

www.SSTAutomation.com
15
5. Configure the properties.
6. Check the mapping buffer and the property names. Use the “Auto Mapping” and “Name Properties in Order”
functions.
7. Save the configuration and download to GT100-MQ-RS through network cable configuration.
Note:
1. Make sure that the GT100-MQ-RS and your computer are in the same network segment.
2. If you can’t discover any gateways, please test the network connection first. Please refer to the note
“How to Use the Ping Command” located on our Support page on the sstautomation.com website.
3. If you can’t discover any gateways, press and hold the configuration button for 3 seconds after powering
on. At this time, the IP address is restored to 192.168.0.10. The device can be searched under the same
network segment as the gateway and computer, and the configuration can be uploaded and downloaded.

www.SSTAutomation.com
16
5 Software Instructions
SST-MQT-CFG is the configuration software which can be used to configure GT100-MQ-RS.
It can be downloaded from the product page or Download page (www.sstautomation.com/Download1/) of the
website.
The software is based on Windows OS.
Operating System: Win7, Win10, Win11.
5.1 Software Interface Description
Double click on the SST-MQT-CFG icon to enter Device Select interface.