C#读写西门子PLC（利用S7.NET）

S7.Net documentation

How to download s7.Net

The official repository is on GitHub (https://github.com/killnine/s7netplus), you can also download the

library directly from NuGet (https://www.nuget.org/packages/S7netplus/).

What is S7.Net

S7.Net is a plc driver that works only with Siemens PLC and only with Ethernet connection. This means that

your plc must have a Profinet CPU or a profinet external card (CPxxx card).

To get started with S7.Net you have to download and include the S7.Net.dll in your project. You can do this

by downloading the NuGet package, or by downloading the sources and compile them.

Create a PLC instance, connect and disconnect

To create an instance of the driver you need to use this constructor:

public Plc(CpuType cpu, string ip, Int16 rack, Int16 slot)

 Cpu: this specify what CPU you are connecting to. The supported CPU are:

public enum CpuType {

 Ip: this contains the IP address of the CPU of external Ethernet card

 Rack: this contains the rack of the plc, that you can find in hardware configuration in Step7

 Slot: this is the slot of the CPU, that you can find in hardware configuration in Step7

Example:

This code creates a Plc object for a S7-300 plc at the IP address 127.0.0.1, that it’s localhost, for a plc that

it’s in rack 0 and a cpu that it’s in slot 2 of the hardware configuration:

Plc plc = new Plc(CpuType.S7300, "127.0.0.1", 0, 2);

Connecting to the PLC

public void Close()

For example this closes the connection:

plc.Close();

The Open() method returns an ErrorCode to check if the operation was successful. You should always

check that it returns ErrorCode.NoError.

These are the types of errors:

public enum ErrorCode

{

NoError = 0,

ReadData = 30,

WriteData = 50

}

Global error handling

Not all methods returns an error. You can check for

public ErrorCode LastErrorCode

and

public string LastErrorString

on every methods that you execute, in order to catch errors while running the driver.

Checking the plc connection is trivial, because you have to check if the PC socket is connected but also if the

PLC is still connected.

The property that you have to check in this case is this:

public bool IsConnected

This property can be checked after you called the method Open(), to check if the connection is still alive.

The library offers several methods to read variables. The basic one and the most used is ReadBytes.

public byte[] ReadBytes(DataType dataType, int db, int startByteAdr, int count)

{

Input = 129,

Output = 130,

Memory = 131,

DataBlock = 132,

Timer = 29,

Counter = 28

}

 db: this is the address of the dataType, for example if you want to read DB1, this field is “1”; if you

want to read T45, this field is 45.

Example:

This method reads the first 200 bytes of DB1:

var bytes = plc.ReadBytes(DataType.DataBlock, 1,0,200);

Example with recursion:

private List<byte> ReadMultipleBytes(int numBytes, int db, int startByteAdr = 0)

{

List<byte> resultBytes = new List<byte>();

int index = startByteAdr;

while (numBytes > 0)

numBytes -= maxToRead;

index += maxToRead;

}

return resultBytes;

}