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https://issues.apache.org/jira/browse/PLC4X-300?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17630943#comment-17630943
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Lukas Ott commented on PLC4X-300:
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This issue has been migrated to https://github.com/apache/plc4x/issues/620
> Plc4x support for RTU/Serial communication for modbus protocol.
> ---------------------------------------------------------------
>
> Key: PLC4X-300
> URL: https://issues.apache.org/jira/browse/PLC4X-300
> Project: Apache PLC4X
> Issue Type: Bug
> Components: Driver-Modbus, examples
> Affects Versions: 0.8.0
> Reporter: Purushotham YB
> Priority: Major
>
> Hi,
> I am using plc4x for one of our projects to develop a module which uses
> plc4x to establish communication with a sensor device using modbus RTU/Serial
> communication.
> I am able to communicate with the device with TCP transport but not able to
> do with RTU/Serial communication.
> I tried to look for some example/documentation on how to use RTU/Serial
> communication in plc4x but could not find any information in the website or
> the web.
> Also looking at the documentation at
> [https://plc4x.apache.org/users/protocols/modbus.html] it is not clear
> whether modbus supports serial transport as it only lists tcp and udp.
>
> |Compatible Transports:| * {{tcp}} (Default Port: 502)
> * {{udp}} (Default Port: 502)|
> Kindly request to clarify if serial is supported in modbus? if so could you
> please point me to an example/documentation which shall be used to understand
> how to use it for serial communication.
> Anyways I tried to use the library/driver plc4j-transport-serial
> [https://plc4x.apache.org/users/transports/serial.html]
> to communicate with device in which the connection is established but it
> fails to read the data with following WANING.
>
> {{2021-06-03-18:13:51.814 [nioEventLoopGroup-2-1] WARN
> io.netty.channel.nio.NioEventLoop - Selector.select() returned prematurely
> 512 times in a row; rebuilding Selector
> org.apache.plc4x.java.transport.serial.SerialPollingSelector@28ecdc0d.}}
> {{2021-06-03-18:13:59.630 [nioEventLoopGroup-2-1] WARN
> io.netty.channel.nio.NioEventLoop - Selector.select() returned prematurely
> 512 times in a row; rebuilding Selector
> org.apache.plc4x.java.transport.serial.SerialPollingSelector@11c9a1fa.}}
> {{My Sample code is as follows.}}
>
> {{ private void plcRtuReader() {}}
> {{ // unit-identifier=1&}}
> {{ String connectionString =}}
> {{ "modbus:serial://COM5?unit-identifier=1&baudRate=19200&stopBits=" +
> SerialPort.ONE_STOP_BIT}}
> {{ + "&parityBits="}}
> {{ + SerialPort.NO_PARITY + "&dataBits=8";}}
> {{ System.out.println("URL:" + connectionString);}}
> {{ try (PlcConnection plcConnection = new
> PlcDriverManager().getConnection(connectionString)) {}}
> {{ if (!plcConnection.getMetadata().canRead()) {}}
> {{ System.out.println("This connection doesn't support reading.");}}
> {{ return;}}
> {{ }}}
> {{ PlcReadRequest.Builder builder = plcConnection.readRequestBuilder();}}
> {{ builder.addItem("value-2", "input-register:1[2]");}}
> {{PlcReadRequest readRequest = builder.build();}}
> {{// CompletableFuture<? extends PlcReadResponse> asyncResponse =
> readRequest.execute();}}
> {{ PlcReadResponse response = readRequest.execute().get();}}
> {{ for (String fieldName : response.getFieldNames()) {}}
> {{ if (response.getResponseCode(fieldName) == PlcResponseCode.OK) {}}
> {{ int numValues = response.getNumberOfValues(fieldName);}}
> {{ // If it's just one element, output just one single line.}}
> {{ if (numValues == 1) {}}
> {{ System.out.println("Value[" + fieldName + "]: " +
> response.getObject(fieldName));}}
> {{ }}}
> {{ // If it's more than one element, output each in a single row.}}
> {{ else {}}
> {{ System.out.println("Value[" + fieldName + "]:");}}
> {{ for (int i = 0; i < numValues; i++) {}}
> {{ System.out.println(" - " + response.getObject(fieldName, i));}}
> {{ }}}
> {{ }}}
> {{ }}}
> {{ // Something went wrong, to output an error message instead.}}
> {{ else {}}
> {{ System.out.println(}}
> {{ "Error[" + fieldName + "]: " +
> response.getResponseCode(fieldName).name());}}
> {{ }}}
> {{ }}}
> {{ System.exit(0);}}
> {{ } catch (PlcConnectionException e) {}}
> {{ e.printStackTrace();}}
> {{ } catch (Exception e) {}}
> {{ e.printStackTrace();}}
> {{ }}}
> {{ }}}
> Thanks a lot for your help.
> Regards,
> Purushotham
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