Modbus TCP/IP

1. Applicable Scenarios

Modbus TCP is a Modbus protocol based on the TCP/IP protocol, usually using Ethernet as the physical layer transmission medium. When a customer is using a Solis inverter on site and needs to test reading the inverter data via MODBUS TCP protocol, the Solis S2-WL-ST can be used, refer to the operation method in this manual.

1.1 Material preparation: 

• Protocol and specification: with Solis inverter MODBUS RS485 communication protocol, inverter manual, S2-WL-ST data logger manual.
• Device: one computer (or other terminal device that can be plugged into a network cable), one router/switch that can provide multiple network ports, and two network cables (the network cable without a protection cover should be selected).

1.2 Debugging tools:

Download and install the debugging tool Modbus Poll by following the link below. Other MODBUS TCP communication software is also available.

https://modbustools.com/download.html

1.3 Installation instructions: 

• According to the S2-WL-ST logger instructions, insert the S2-WL-ST data logger into the COM port of the normal inverter, and insert the network cable into the rear network port to connect the router or computer.
• The specific operation method may vary depending on the device model and network topology. You are advised to refer to the device manual or consult related technical personnel.

2. The method to confirm the IP address of the S2-WL-ST data logger

2.1 Default IP address: 

• The default IP address of S2-WL-ST logger is 10.10.100.254
• Cable connection: Insert network cable into the S2-WL-ST logger port, and connect the other end of the network cable to the computer.
• Set Internet Protocol Version 4 in your computer's Ethernet connection properties to automatically obtain an IP address.
• In this case, no matter whether the data logger is configured with a wireless network, you can use this IP address to test the TCP connection.

2.2 Static IP address:

• By default, the S2-WL-ST logger uses a dynamic IP address to access the LAN. You can set it to a static IP address in the following ways.
• Initial cable connection: Insert network cable into the data logger port, and connect the other end of the network cable to the computer.
• Set Internet Protocol Version 4 in your computer's Ethernet connection properties to automatically obtain an IP address.
• Enter the URL 10.10.100.254 in the browser, log in to the built-in web page of the S2-WL-ST logger. The user name is admin and the initial password is 123456789.
• Click the option "LAN Settings" under "Advanced", and enter the static IP address information (be careful not to repeat the IP address of the computer). Click "Save" to save the settings, and the page prompts you to set them successfully。
• Switch the wiring mode: Connect the S2-WL-ST logger and the computer to the same router network port, and the data logger connects to the network based on the configured static IP address. 

You can use the Modbus Poll tool on the computer side and connect the TCP through the static IP of the S2-WL-ST logger.

3. Introduction to Modbus poll

3.1 Installation and registration：

• After the installation is complete, open the software. After opening the main window interface is shown as the following figure.
• Click “Connect” in “Connection” on the menu bar, pop-up registration window, click "Order" to jump to the official website registration page, purchase the service to obtain the registration key, return to the page to enter the key, and click OK to complete the registration (if you only use this prompt box temporarily, you can close this prompt box to obtain 30-day trial permission).
• Directly enter the main window after registration, as shown below. Close the dialog box and proceed to the next step.

3.2 Parameter setting

• Click "Read/Write Definition" in the "Setup" menu to set parameters, and the parameter settings dialog box pops up.
• Setup as defined below:
  • Slave: Address of the Modbus slave machine to be accessed, corresponding to the ID value in the main window. The default value is 1.
  • Function: Register function code selection. For this demonstration, select 03 function code (read hold register).
  • Address: Register initial address, starting from 0 by default. This operation demonstration, according to the MODBUS protocol address of Ginlong grid-tied inverter, set the starting address to 3000.
  • Length: Continuous number of registers, default is 10, corresponding to the number of channels of the configuration software. For this demonstration, select the display of 50 consecutive addresses. 
  • Scan Rate: read data cycle. Default is 1000ms. 
• As shown as the following pictures, click the OK button and the simulation window will display a list of defined registers.

3.3 Display setting

• By default, register data is displayed in Signed mode (hexadecimal unsigned binary), and the data range is -32768 to 32767. If the user wants to Display in other numerical ways, select the menu “display”, as shown in the following picture:

3.4 Serial connection

• Click “Connect” in the menu “Connection” to make a serial connection, and the connection settings dialog box will pop up.
• Set as the following definition: 
• Connection: select the Modbus TCP/IP mode. 
• Response Timeout: indicates the read timeout. The default is 1000ms. If the slave station does not return data within the timeout period, the communication is considered to have failed.
• Delay between Polls: indicates the minimum interval between polls. The default value is 10ms.
• Remote Modbus Server: represents the network setting of the terminal slave device in TCP/IP mode.
• IP Address: indicates the slave IP address in TCP/IP mode. That is, the S2-WL-ST logger IP address confirmed in the second chapter.
• Port: indicates the slave network port in TCP mode. The default port number of the S2-WL-ST logger is 502.
• Click the OK button after confirming the setting, and if you connect and read correctly, the main window will display information about the read register.

3.5 View communication data frames：

• Click “Communication” in the “Display” menu. The serial port to send and receive data frames monitoring information dialog box "Communication Traffic" will pop up, which can be used to view and analyze the data frames sent and received. As shown in the following picture:

The first 6 bits are the sequence number of the data frame. Rx represents the received data frame. Tx represents the sent data frame.

3.6 Disconnect

• Click “Disconnect” in the menu “Connection” to disconnect and end the test, and the red "No Connection" appears in the main window to indicate the unconnected status.