webpac-docs

(web based plc data access)

By Benjamin Proemmer

Webpac is a software which offers an web-interface for accessing Step7 PLC's. This interface enables you to read and write to/from PLC. Furthermore it supports the functionality to subscribe for events if data changes.

The project is hosted on github webpac

running the application

To start webpac, you have to run the following command:

after this the application runs in the command window:

Absolute (address based access)

The first method to read and write data is by its absolute address. To address a value in the PLC you have to specify the area and the type.

Area

Area	Name
DB[Number]	datablock
FB	Flags
IB	Input
OB	Output
TB	Timer
CB	Counter

Address

[Code][Offset][_Length]

Code	Type
BIT	Boolean
B	Byte
BYTE	Byte
C	Char
CHAR	Char
DATE	Date
DT	DateTime
DATETIME	DateTime
DI	Double Integer
DINT	Double Integer
I	Integer
INT	Integer
R	Real
REAL	Real
TIMEBCD	S7 Time
S	String
STRING	String
T	Time
TIME	Time
TOD	TimeOf Day
W	Word
WORD	Word
CT	Counter
COUNT	Counter

Symbolic (symbol based access)

The second access method is by its symbolic name. For this, you have to create a data-mapping file. The structure of this file is an C# class with properties. To create such a file is very easy, you could use a tool from insite-gmbh called AWLConverter. This tool extracts the data from the Simatic Manager and converts it to the representation we use.

##web api

To visualize and test the web api we added swagger support. Whit this, you can also generate a proxy to easily call webpac from your C# application.

##Configuration

Logging

In this section you can configure the logging for the application. (For details have a look at docs.asp.net)

  "Logging": {
    "IncludeScopes": false,
    "LogLevel": {
      "Default": "Information",
      "System": "Information",
      "Microsoft": "Information"
    }
  }

Global

The Global section can be used to deactivate some features. (The shown settings are default)

  "Global": {
      "UseSignalR": true,
      "UseWebSockets": true,
      "UseSwagger ":  true,
      "UseLogFiles" :  true
    }

• UseSignalR: If false, SignalR is not activated and data change call back is not available.
• UseWebSockets: If false, wepac do not use websockets and so it tries to find a other supported method.
• UseSwagger: If false, swagger is not activated, an so u could not use swagger ui.
• UseLogFiles: If false, no log file will be created. If true, webpac uses the nlog.config file for log file configuration.

Plc

This section specifies the connection parameter to the PLC.

  "Plc": {
    "ConnectionString": "Data Source=127.0.0.1:102,0,2",
    "ConnectOnStartup": true,
    "ReconnectOnConnectionLost": true,
    "ReconnectIntervall":  5000
  }

• ConnectionString: Defines the address to the PLC. Syntax: [IP]:[PORT],[RACK],[SLOT]
• ConnectOnStartup: If this value is true, webpac try connecting to PLC at the application start.
• ReconnectOnConnectionLost: If this value is true, webpac tries to reconnect, when PLC connection goes down.
• ConnectReconnectIntervallOnStartup: This value specifies the connection retry interval.

RuntimeCompiler

  "RuntimeCompiler": {
    "Location": "C:\\webpac\\data",
    "Usings": [
      "System",
      "Papper.Attributes"
    ]
  }

• Location: This value specifies the Location of the symbolic file (C# class files).
• Usings: This is an array of usings depending of the class files you want compile.

Authentication

  "Auth": {
    "KeyFile": "C:\\webpac\\data\\sec.key",
    "TokenValidatenTimeinMinutes": 1440 ,
    "Users": [
      {
        "Type": "ReadOnly",
        "Username": "ReadOnlyUsername",
        "Password": "ReadOnlyPassword"
      },
      {
        "Type": "ReadWrite",
        "Username": "ReadWriteUsername",
        "Password": "ReadWritePassword"
      }
    ]
  }

• KeyFile: This value specifies the Location of the key file for the authentication token (this file will be created on first start).
• TokenValidatenTimeinMinutes: This value specifies the validation time of the token.
• Users.Type: Select the access level for the api calls [Valid parameters are ReadOnly, ReadWrite]
• Users.Username: Name of the user for sign in.
• Users.Password: Password for the specified user.

##File based Logging

To write to log files, webpac use NLog. (For configuration details, see the webpage of the project.)

##Used Libraries

To get the PLC access we use two libraries as the following image describe.

###Papper

Papper is a data mapper which maps a C# class to a PLC data block. This package is also available as a nuget package.

Dacs7

DacS7 is a low level component which handles the communication to the PLC and is available as a nuget package.