Reactive S7 PLC Communications Library

S7PlcRx is a library that provides a simple interface to communicate with Siemens S7 PLCs.

• Read and Write to PLC
• Read from PLC with Reactive Subscription

S7PlcRx is available on NuGet.

In the Siemens PLC program you need to enable PUT/GET communication in the PLC settings. You will also need to set any DBs you want to access to be non-optimized.

Install-Package S7PlcRx

dotnet add package S7PlcRx

using S7PlcRx;

var plc = new RxS7(S7PlcRx.Enums.CpuType.S71500, "PLC_IP_ADDRESS", 0, 5);
// Add Tag without Polling
plc.AddUpdateTagItem<double>("Tag0", "DB500.DBD0").SetTagPollIng(false);
// Add Tag with Polling
plc.AddUpdateTagItem<double>("Tag1", "DB500.DBD8");

plc.IsConnected
    .Where(x => x)
    .Take(1)
    .Subscribe(async _ =>
    {
        Console.WriteLine("Connected");

        // Read Tag Value manually
        var tag0 = await plc.Value<double>("Tag0");
    });

// Subscribe to Tag Values
plc.Observe<double>("Tag0").Subscribe(x => Console.WriteLine($"Tag0: {x}"));
plc.Observe<double>("Tag1").Subscribe(x => Console.WriteLine($"Tag1: {x}"));
// Start Polling on previously disabled Tag
plc?.GetTag("Tag0")?.SetTagPollIng(true);

You can also use the S7xxxx static classes to setup the PLC. For example, S7PlcRx.S71500.Create(...... to setup a S7-1500 PLC.

plc.AddUpdateTagItem(typeof(double), "Tag0", "DB500.DBD0");

plc.AddUpdateTagItem<double>("Tag0", "DB500.DBD0").SetTagPollIng(false)
   .AddUpdateTagItem(typeof(double), "Tag1", "DB500.DBD8");

plc.RemoveTagItem("Tag0");

Polling is enabled by default when a Tag is added. You can disable and enable polling on a Tag at any time.

// Create a new Tag and with no Polling
plc.AddUpdateTagItem<double>("Tag0", "DB500.DBD0").SetTagPollIng(false);

// Set Polling on Tag
plc?.GetTag("Tag0")?.SetTagPollIng(true);

// Stop Polling on Tag
plc?.GetTag("Tag0")?.SetTagPollIng(false);

plc.Value<double>("Tag0", 1.0);

// Get CPU Info from PLC Async
var cpuInfo = await plc.CpuInfo();

// Get CPU Info from PLC Reactive
plc.GetCpuInfo().Subscribe(info =>
    {
    });

This returns a CpuInfo string Array with the following values: AS Name, Module Name, Copyright, Serial Number, Module Type Name, Order Code, Version.

The Watchdog is a feature that writes a value to a specific address in the PLC at a set interval. This can be used to keep the PLC alive and prevent it from going into stop mode.

The functionallity of the PLC is down to the user to implement.

The recommended way to use the Watchdog is to use a timer to decrement a value in the PLC. If the value reaches 0 then the PLC can be stopped. The Watchdog will always write a value back to the PLC to reset the timer and resume normal operation.

var plc = new RxS7(S7PlcRx.Enums.CpuType.S71500, "PLC_IP_ADDRESS", 0, watchDogAddress, 5, watchDogValueToWrite, watchDogInterval);

The Watchdog is disabled by default. To enable the Watchdog set the watchDogAddress, it must be an address of type DBW. The watchDogInterval is the time in seconds between each write and the watchDogValueToWrite is the value to write to the PLC.

• Bool - DB?.DBX?.?
• Byte - DB?.DBB?
• Byte[] - DB?.DBB? set length to number of bytes when creating array tags - example AddUpdateTagItem<byte[]>(PlcData, "DB100.DBB0", 64) - creates a tag with 64 bytes
• Int - DB?.DBW?
• Int[] - DB?.DBW?
• UInt - DB?.DBW?
• UInt[] - DB?.DBW?
• DInt - DB?.DBD?
• DInt[] - DB?.DBD?
• UDInt - DB?.DBD?
• UDInt[] - DB?.DBD?
• Real - DB?.DBD?
• Real[] - DB?.DBD?
• LReal - DB?.DBD?
• LReal[] - DB?.DBD?
• String - TODO - for the time being use a Byte Array
• Word - DB?.DBW?
• Word[] - DB?.DBW?
• DWord - DB?.DBD?
• DWord[] - DB?.DBD?

Further types will be added in the future.

• Logo-0BA8
• S7-200
• S7-300
• S7-400
• S7-1200
• S7-1500