Guide:
For inverters and instrumentation equipment, both support 485 serial port communication, so how to judge which protocol the slave equipment supports? It is usually divided into two ways to judge: 1. Refer to the equipment parameters 2. View from the equipment communication message. In this article, we take Delta's MH300 series inverter as an example.
View from the device communication parameters
Be sure to prepare a manual before using the device, so that it is easy to query the parameters and set the parameters. As shown in Figure 1, find the communication parameters, 09-04 is the communication format, 2 is the ASCll communication format, and 3 is the Modbus RTU communication format, from which it can be seen that there are two protocols supported by the 485 communication of Delta MH300 series inverter.
Figure 1
View the device communication packets
Figure 2 shows the Modbus RTU packet frame format, and if the device uses this packet frame format, it is the Modbus RTU communication protocol.
Figure 2
Usually we will choose Modbus RTU to communicate, because Modbus RTU messages are standard, fixed format, some brands of PLC software come with communication library instructions, writing programs is relatively simple, no need to write a lot of programs, such as Siemens' 200, 200smart, 1200, 1500 these PLCs, the software itself integrates Modbus RTU communication slave and master library instructions, directly call the library for programming.
The RTU mode of Delta's MH300 series inverter is shown in Figure 3.
Figure 3
The ASCll mode of Delta's MH300 series inverter is shown in Figure 4.
Figure 4
For free ports, different packets are different, and you need to write programs according to the packet format, which is relatively difficult for novices.
Summary:
The above is how to judge whether the 485 slave device supports modbus rtu communication content, after getting the equipment, go to the corresponding official website to download the manual, according to the parameter settings or message format on the manual, to determine which communication protocol needs to be used for communication, the current equipment uses Modbus RTU communication more, if there are a variety of communication protocol options, you can consider using a relatively simple Modbus RTU communication protocol for communication. If there is any error in the content of the article or if you do not understand it, please contact us.
Copyright Notice:The author of this article is trained - Zou Zhirui, please do not reprint without permission, offenders will be investigated!
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