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| <div class="sect1"> |
| <h2 id="about_plc4go">About PLC4Go</h2> |
| <div class="sectionbody"> |
| <div class="paragraph"> |
| <p><code>PLC4Go</code> is a sub-project of <code>PLC4X</code> with implementations based on <code>Go</code>.</p> |
| </div> |
| <div class="paragraph"> |
| <p>One of PLC4X’s core principals is, that an application using PLC4X should be independent of the PLC or protocol being used.</p> |
| </div> |
| <div class="paragraph"> |
| <p>When addressing a resource on a remote there are two parts that are dependent on the protocol and the type of PLC:</p> |
| </div> |
| <div class="ulist"> |
| <ul> |
| <li> |
| <p>Addressing the PLC itself</p> |
| </li> |
| <li> |
| <p>Addressing a resource on the PLC</p> |
| </li> |
| </ul> |
| </div> |
| <div class="paragraph"> |
| <p>Providing this independence to addressing the PLC itself is completely handled by the <code>PlcDriverManager</code> the application requests a connection from.</p> |
| </div> |
| <div class="paragraph"> |
| <p>Hereby the design of the <code>url string</code> passed to the <code>getConnection</code> method is greatly inspired by <code>JDBC</code>.</p> |
| </div> |
| <div class="paragraph"> |
| <p>The protocol prefix of the url specifies the type of driver being used.</p> |
| </div> |
| <div class="paragraph"> |
| <p>For example, when connecting to a Siemens PLC using the S7/Step7 Protocol, the url: <code>s7://192.42.0.98/1/2</code> causes the driver manager to create a S7 connection instance. |
| The part behind the <code>:</code> is hereby used by the driver implementation to configure that particular connection.</p> |
| </div> |
| <div class="paragraph"> |
| <p>For a S7 connection, for example, this is <code>IP address/host name</code>/<code>rack number</code>/<code>slot number</code>. For different types of connections this url structure will greatly differ.</p> |
| </div> |
| <div class="paragraph"> |
| <p>As mentioned above, the second platform dependent information is the address of resources on a PLC. |
| The format of an address greatly depends on the type of connection. Therefore <code>parseAddress</code> is one of the only methods defined in the <code>PlcConnection</code> interface any connection has to implement.</p> |
| </div> |
| <div class="paragraph"> |
| <p>This method returns an object implementing the <code>Address</code> interface which then can be used by the same connection to identify remote resources.</p> |
| </div> |
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| <div class="content"> |
| <img src="../images/plc4x-architecture.png" alt="plc4x architecture" width="1000" height="574"/> |
| </div> |
| </div> |
| <div class="sect2"> |
| <h3 id="usage">Usage</h3> |
| <div class="paragraph"> |
| <p>Below code example connects to a remote Siemens S7 PLC using the S7/Step7 protocol and then reads the state of the <code>inputs</code> and <code>outputs</code> from this.</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="prettyprint highlight"><code data-lang="go">func HellpPlc4go() { |
| driverManager := plc4go.NewPlcDriverManager() |
| driverManager.RegisterDriver(modbus.NewModbusDriver()) |
| driverManager.RegisterTransport(tcp.NewTcpTransport()) |
| |
| // Get a connection to a remote PLC |
| crc := driverManager.GetConnection("modbus-tcp://192.168.23.30") |
| |
| // Wait for the driver to connect (or not) |
| connectionResult := <-crc |
| if connectionResult.Err != nil { |
| t.Errorf("error connecting to PLC: %s", connectionResult.Err.Error()) |
| return |
| } |
| connection := connectionResult.Connection |
| |
| // Try to ping the remote device (This block is just optional) |
| pingResultChannel := connection.Ping() |
| pingResult := <-pingResultChannel |
| if pingResult.Err != nil { |
| t.Errorf("couldn't ping device: %s", pingResult.Err.Error()) |
| return |
| } |
| |
| // Make sure the connection is closed at the end |
| defer connection.Close() |
| |
| // Prepare a read-request |
| readRequest, err := connection.ReadRequestBuilder(). |
| AddItem("field1", "holding-register:1:REAL"). |
| AddItem("field2", "holding-register:3:REAL"). |
| Build() |
| if err != nil { |
| t.Errorf("error preparing read-request: %s", connectionResult.Err.Error()) |
| return |
| } |
| |
| // Execute a read-request |
| rrc := readRequest.Execute() |
| |
| // Wait for the response to finish |
| rrr := <-rrc |
| if rrr.Err != nil { |
| t.Errorf("error executing read-request: %s", rrr.Err.Error()) |
| return |
| } |
| |
| // Do something with the response |
| value := rrr.Response.GetValue("field") |
| |
| // Do something sensible with the information |
| fmt.Printf("\n\nResult: %f\n", value) |
| }</code></pre> |
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