![]() ![]() ![]() Once you resolve the connection between the computer and the server device, the connection from the data logger should work. Connect the computer to the same network and attempt to open a Modbus TCP connection to the problem server device. Provided the data logger has a working network connection, further troubleshooting can be done with a computer running Modbus software. The socket returned from TCPOpen() should be a number less than 99. If you have a failed socket connection for Modbus TCP, check your TCPOpen() instruction. For Modbus TCP, it indicates a failed socket connection. Right-click on the Modbus node, and select the Add > 'Modbus Server' Device option, as shown below. You can create a Modbus Server device as follows: In the Project Explorer, search for the Devices > Communications > Modbus node. A Modbus Server device can accept requests from multiple Modbus Client devices simultaneously. ![]() For serial connections, this error may indicate an invalid COM port number. A Modbus Server device does not initiate communication with other Modbus Devices, but stores data that is accessible locally and remotely through Modbus Client devices. Result code -11 occurs when the data logger is unable to open the COM port specified. Try requesting all of the registers together. The result is that the device will report an error when you try selectively polling registers. Instead, they are hard coded to respond to certain Modbus messages. Some devices do not fully implement parsing Modbus commands. With 32-bit data types, it requests twice as many registers as the length.Īn uncommon cause for the -02 result is a device with an incomplete implementation of Modbus. The ModbusClient() instruction uses length as the number of values to poll. Also, too long of a length can trigger this error. Refer to the earlier section about register number and consult the device documentation for support information. One possibility, is a mistake in your program on the starting register number. The illegal data address error occurs if the server rejects the combination of starting register and length used. Instead, they are hardcoded to respond to certain Modbus messages. It is common for devices to have holding registers where read-only and read/write registers are mapped next to each other.Īn uncommon cause for the -01 result is a device with an incomplete implementation of Modbus. If the function code is supported, make sure you are not trying to write to a register labeled as read-only. ![]() Different devices support different functions (consult the device documentation). Modbus RTU over TCP is a non-standard variant of Modbus TCP that includes the. The illegal function error is reported back by a Modbus server when either it does not support the function at all, or does not support that function code on the requested registers. Modbus was developed as a communication protocol for Modicon PLC Devices. A positive result code indicates no response was received. ModbusClient() displays these codes as a negative number. Modbus defines several error codes, which are reported back to a client from a server. Further information on Modbus can be found at: Whether you are connecting via Modbus to a solar inverter, power meter, or flow meter, the information provided here can help you overcome the challenges, and successfully gather data into a Campbell data logger. The default value is 127.0.0.1 (localhost).Most of the difficulties with Modbus communications arise from deviations from the standards, which are not enforced within Modbus. The host name or IP address (in standard IPv4 format) of the Modbus Server device. The name used to list the Modbus Server device in the Project Explorer. These are listed below in the next step.Ĭonfigure the properties according to their description: Parameter The Parameter Configuration dialog appears, allowing you to configure the properties of the server. In the Project Explorer, search for the Devices > Communications > Modbus node. You can create a Modbus Server device as follows: A Modbus Server device does not initiate communication with other Modbus Devices, but stores data that is accessible locally and remotely through Modbus Client devices. This means that the communication protocol is not tied to the hardware of a. The Modbus Server device represents a server-role device connection, according to the Modbus Protocol terminology. Modbus/TCP is a communication protocol that is supported by most industrial devices. ![]()
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