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https://issues.apache.org/jira/browse/PLC4X-156?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16988750#comment-16988750
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Christofer Dutz commented on PLC4X-156:
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So I would update the Driver to accept the mentioned "sleaveId" as a parameter
... does it also make sense to change the default from 0 to 1?
> The unitId (device id/slave id) is hardcoded to 0 which is the broadcast id
> in modbus
> -------------------------------------------------------------------------------------
>
> Key: PLC4X-156
> URL: https://issues.apache.org/jira/browse/PLC4X-156
> Project: Apache PLC4X
> Issue Type: Bug
> Components: Driver-Modbus
> Reporter: Alvaro del Castillo
> Assignee: Christofer Dutz
> Priority: Critical
> Labels: config
> Attachments: Plc4XModbusProtocol.java
>
>
> Trying to use the modbus driver, it is always trying to read and write from
> the slave 0 in the modbus slave/server. This identifier is the one used for
> broadcasting reads and writes to all the slaves in the modbus network. In
> modbus TCP this identifier is not needed, but it is needed to support legacy
> devices.
> And testing with with some modbus serves like:
> [https://pypi.org/project/pyModSlave|https://pypi.org/project/pyModSlave/]
> and in the second case, if you try to read a register:
> {noformat}
> 2019-11-27 08:29:29,837 ERROR modbus.handle_request Thread-1 invalid request:
> Function 3 can not be broadcasted{noformat}
> This unitId should be a param but if it must be hardcoded, changing it to *1*
> is a fix. But in some cases, you could need a
> specific id to connect to a device. For example, for the XY-MD02 sensor
> connected via serial to a Modbus TCP client, in order to read the values from
> the sensor you need to provide the right device id (in this case is also 1,
> but it could change).
> The unitId is defined in:
> [https://github.com/apache/plc4x/blob/develop/plc4j/protocols/modbus/src/main/java/org/apache/plc4x/java/modbus/netty/Plc4XModbusProtocol.java#L92]
> I have tested in 0.4.0 release that changing the unitId to *1* fixes the
> problem with modbus servers. I have attached the file with this minor
> modification.
> I can send a PR if you find the fix useful.
> Thanks!
>
>
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