PLC and PC communication connection

First, the PLC is placed in the stop mode, and the PLC is connected with the programming software. If it can be connected, it indicates that the RS485 converter is wired correctly. Otherwise, it may be the RS485 +, - the wrong adjustment and retry, to ensure that the hardware wiring is correct, you can use Serial port debugging software or Modbus master station simulation software test, if the test is no problem, it is a problem with your host computer code.

At present, people mainly use the following three ways to realize the interconnection communication between PLC and PC:

First, through the use of the system protocol and network adapter provided by the PLC developer to achieve the interconnection communication between PLC and PC. However, since the communication protocol is not disclosed, the interconnection communication must use the host computer configuration software provided by the PLC developer and use peripherals supporting the corresponding protocol. It can be said that this method is tailored by PLC developers for their own products, so it is difficult to meet the needs of different users.

Second, the use of the current general-purpose PC configuration software, such as Kingview, InTouch, WinCC, force control, etc., to achieve the interconnection communication between PLC and PC. The configuration software has been widely used in the field of PC monitoring due to its powerful functions, friendly interface and simple development, but the price is generally expensive. The configuration software itself does not have the ability to directly access PLC registers or other smart meters and must be implemented with the help of I/O drivers. In other words, the I/O driver is a bridge between the configuration software and devices such as PLCs or other smart meters. It is responsible for collecting real-time data from the device and issuing operation commands to the device. Its reliability will directly affect the configuration software. Performance. However, in most cases, the I/O driver is device-dependent, that is, the driver for a certain PLC cannot drive other kinds of PLCs, so the flexibility of the configuration software is also limited.

Third, the use of the standard communication port provided by the PLC manufacturer and the user-defined free port communication mode to achieve the interconnection communication between the PLC and the PC. This way, the user-defined communication protocol does not require additional investment and flexibility, and is especially suitable for small-scale control systems.