Create a New Project at RT-Thread Studios, choose Example etherkit_modbus_tcpip
Configure EtherKit FSP
2.1. Update location of FSP Configurator
2.2. Select sc_v2025-01_fsp_v2.2.0
Follow the FSP Configuration Instructions and RT-Thread Settings Configuration steps at https://github.com/RT-Thread-Studio/sdk-bsp-rzn2l-etherkit/tree/master/projects/etherkit_modbus_tcpip
Go to Debug Configuration. This is to “update” to using new version of J-Link (older versions may not support EtherKit. Need to copy the whole J-Link folder [C: > Program Files > SEGGER > Jlink_V586] into C:/RT-ThreadStudio/repo/Extract/Debugger_Support_Packages/SEGGER/J-Link. Then change the Actual executable. If successful, the Executable path will look like in the image below. ${debugger_install_path}/$$(jlink_debugger_relative_path)
Note: If you don’t do this step and is using older versions of J-Link and it does not support EtherKit, you might encounter this issue when you try to flash download the program:
Connect the EtherKit to your PC as follows:
1. USB Type-B cable (PC to ARM Emulator)
2.JTAG Connect Card (from ARM Emulator)
2x10 ribbon cable (from JTAG Connect Card to JTAG of EtherKit)
3. Power the EtherKit (9 to 24V DC).
PC – [USB TypeB] – ARM Emulator – [JTAG Connect Card] – [20-pin Ribbon Cable] – EtherKit <- POWER
Build the project and flash download
You can verify that the Etherkit’s able to be programmed by changing the LED blinking delay time.
Now plug in ethernet cable to ETH0 of EtherKit, into your PC.
Also, plug in USB type-C to USB-TTL of EtherKit, into your PC.
I set the Ethernet port’s IP to 192.168.137.10
On the RT-Thread Studios, open a terminal, press reset on the Ethernet and type ifconfig.
Now, I am assigning an IP address (192.168.137.11) to the EtherKit, in the same subnet as my Ethernet Port with IP 192.168.137.10, and 255.255.255.0 is the net mask.
Follow the steps on using modbus_tcp_test and Modbus Poll Software at
https://github.com/RT-Thread-Studio/sdk-bsp-rzn2l-etherkit/tree/master/projects/etherkit_modbus_tcpip
End result:

EtherKit as Modbus Master, reading from MOXA

2
Now we are using the coding from the EtherKit as modbus TCP slave example.
(Because it has already the coding to for network initialization [ifconfig, setting IP for the EtherKit])
But we are adding a modbus_master.c file (coding for EtherKit as master).
I add it under board > ports > modbus > tcp_modbus.
Coding can be found at Coding section.
Copy the code from read from MOXA FC04.
Note that we are using Function Code 04, to read input registers of MOXA.
Then build, and flash.
The EtherKit is plugged into a switch, which assigns an IP of 192.168.101.39.
Also, try to ping the MOXA at 192.168.101.100.
Now run modbus_master_start

EtherKit as Modbus Master, reading from WAGO

Now for reading from WAGO is a little different, that is because the IP given to the EtherKit is not of the same subnet as WAGO at 192.168.137.x. Therefore, there will be one additional step that is to set the IP manually for the EtherKit.
Copy the code from read from wago27 FC03.
Note that we are using function code 03, to read holding registers from WAGO.
Build and flash.
The EtherKit is also plugged into the switch, which gives the EtherKit IP address of 192.168.101.39. So now we need to set the IP of the EtherKit to be at the same subnet as WAGO.
Also, verify that we are able to ping the WAGO we are reading, eg. 192.168.137.27
Before this, have to make sure that the WAGO has been set to be a modbus slave.
Run modbus_master_start.
It reads 27 because I set the value to 27.
Verify by changing the values.