# Modbus RTU problem in 8.0.4 **URL:** \ **Category:** Ignition\ **Tags:** ignition80\ **Created:** [October 1, 2019, 6:28am UTC](https://forum.inductiveautomation.com/t/modbus-rtu-problem-in-8-0-4/28683 "2019-10-01T06:28:12Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![DavidWisely](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/davidwisely/32/10482_2.png) [@DavidWisely](https://forum.inductiveautomation.com/u/DavidWisely)\ **Post date:** [October 1, 2019, 6:28am UTC](https://forum.inductiveautomation.com/t/modbus-rtu-problem-in-8-0-4/28683/1 "2019-10-01T06:28:12Z")
I just upgraded from 8.0.1 to 8.0.4 and now my Modbus RTU device wont start. It keeps coming up with the error below. It worked fine before the upgrade. I’ve tried restarting the gateway, restarting the computer, creating a new device. Every time, this error keeps appearing. Anyone know what I should try next? ```auto DeviceManagerNamespace 01Oct2019 15:48:06 Device 'Altona_Modbus' failed to start java.lang.NoClassDefFoundError: Serialio/SerialConfig at com.inductiveautomation.xopc.drivers.modbus2.serial.ModbusRTUDriver.(ModbusRTUDriver.java:24) at com.inductiveautomation.xopc.drivers.modbus2.configuration.ModbusRtuDriverType.createDriver(ModbusRtuDriverType.java:50) at com.inductiveautomation.ignition.gateway.opcua.server.DriverAdapter.startup(DriverAdapter.kt:128) at com.inductiveautomation.ignition.gateway.opcua.server.DeviceManagerNamespace$DeviceAddressSpace.onStartup(DeviceManagerNamespace.kt:267) at com.inductiveautomation.ignition.common.lifecycle.AbstractLifecycle.startup(AbstractLifecycle.java:18) at com.inductiveautomation.ignition.gateway.opcua.server.DeviceManagerNamespace.createAndStartupDevice(DeviceManagerNamespace.kt:162) at com.inductiveautomation.ignition.gateway.opcua.server.DeviceManagerNamespace.access$createAndStartupDevice(DeviceManagerNamespace.kt:40) at com.inductiveautomation.ignition.gateway.opcua.server.DeviceManagerNamespace$DeviceSettingsRecordListener$recordUpdated$1.invokeSuspend(DeviceManagerNamespace.kt:222) at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33) at kotlinx.coroutines.DispatchedTask.run(Dispatched.kt:241) at kotlinx.coroutines.EventLoopImplBase.processNextEvent(EventLoop.common.kt:270) at kotlinx.coroutines.BlockingCoroutine.joinBlocking(Builders.kt:79) at kotlinx.coroutines.BuildersKt__BuildersKt.runBlocking(Builders.kt:54) at kotlinx.coroutines.BuildersKt.runBlocking(Unknown Source) at kotlinx.coroutines.BuildersKt__BuildersKt.runBlocking$default(Builders.kt:36) at kotlinx.coroutines.BuildersKt.runBlocking$default(Unknown Source) at com.inductiveautomation.ignition.gateway.opcua.server.DeviceManagerNamespace$DeviceSettingsRecordListener.recordUpdated(DeviceManagerNamespace.kt:219) at com.inductiveautomation.ignition.gateway.opcua.server.DeviceManagerNamespace$DeviceSettingsRecordListener.recordUpdated(DeviceManagerNamespace.kt:209) at com.inductiveautomation.ignition.gateway.localdb.PersistenceInterfaceImpl.notifyRecordUpdated(PersistenceInterfaceImpl.java:178) at com.inductiveautomation.ignition.gateway.redundancy.RedundantPersistenceInterfaceImpl.doNotifyRecordUpdated(RedundantPersistenceInterfaceImpl.java:88) at com.inductiveautomation.ignition.gateway.redundancy.RedundantPersistenceInterfaceImpl$RecordUpdateListener.recordUpdated(RedundantPersistenceInterfaceImpl.java:295) at com.inductiveautomation.ignition.gateway.redundancy.RedundantPersistenceInterfaceImpl$RecordUpdateMessage.notify(RedundantPersistenceInterfaceImpl.java:346) at com.inductiveautomation.ignition.gateway.redundancy.RedundantPersistenceInterfaceImpl$RecordUpdateListener.receiveCall(RedundantPersistenceInterfaceImpl.java:278) at com.inductiveautomation.ignition.gateway.redundancy.QueueableMessageReceiver.receiveCall(QueueableMessageReceiver.java:47) at com.inductiveautomation.ignition.gateway.redundancy.RedundancyManagerImpl.dispatchMessage(RedundancyManagerImpl.java:852) at com.inductiveautomation.ignition.gateway.redundancy.RedundancyManagerImpl$ExecuteTask.run(RedundancyManagerImpl.java:924) at com.inductiveautomation.ignition.common.execution.impl.BasicExecutionEngine$ThrowableCatchingRunnable.run(BasicExecutionEngine.java:518) at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) at java.base/java.util.concurrent.FutureTask.run(Unknown Source) at java.base/java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(Unknown Source) at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) at java.base/java.lang.Thread.run(Unknown Source) ``` ---
**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\ **Post date:** [October 1, 2019, 11:43am UTC](https://forum.inductiveautomation.com/t/modbus-rtu-problem-in-8-0-4/28683/2 "2019-10-01T11:43:45Z")
Did you lose the Serial Support (gateway) module during the upgrade? ---
**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\ **Post date:** [October 1, 2019, 12:46pm UTC](https://forum.inductiveautomation.com/t/modbus-rtu-problem-in-8-0-4/28683/3 "2019-10-01T12:46:11Z")
Yikes, this is just a bug. You’ll have to downgrade until we get it fixed. ---
**Author:** ![DavidWisely](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/davidwisely/32/10482_2.png) [@DavidWisely](https://forum.inductiveautomation.com/u/DavidWisely)\ **Post date:** [October 1, 2019, 11:28pm UTC](https://forum.inductiveautomation.com/t/modbus-rtu-problem-in-8-0-4/28683/4 "2019-10-01T23:28:46Z")
Thanks for your help. Do you think it will work in version 8.0.3, or do I have to go back to 8.0.1 that was working before? ---
**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\ **Post date:** [October 1, 2019, 11:51pm UTC](https://forum.inductiveautomation.com/t/modbus-rtu-problem-in-8-0-4/28683/5 "2019-10-01T23:51:09Z")
I think 8.0.3 will work. This has to do with the new serial library that we switched to and that was done in 8.0.4. ---
**Author:** ![DavidWisely](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/davidwisely/32/10482_2.png) [@DavidWisely](https://forum.inductiveautomation.com/u/DavidWisely)\ **Post date:** [October 2, 2019, 3:55am UTC](https://forum.inductiveautomation.com/t/modbus-rtu-problem-in-8-0-4/28683/6 "2019-10-02T03:55:19Z")
Thanks Kevin, I’ve only got a few values to read over Modbus so I’ve just written a script using the system.serial functions and that’s working ok at the moment. I’ll change back to to the Modbus RTU device if it’s fixed in version 8.0.5 ---
**Author:** ![DavidWisely](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/davidwisely/32/10482_2.png) [@DavidWisely](https://forum.inductiveautomation.com/u/DavidWisely)\ **Post date:** [November 13, 2019, 3:30am UTC](https://forum.inductiveautomation.com/t/modbus-rtu-problem-in-8-0-4/28683/7 "2019-11-13T03:30:01Z")
Hi @Kevin.Herron. Do you know if this has been fixed now? Will it work if I upgrade to version 8.0.5? or 8.0.6? ---
**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\ **Post date:** [November 13, 2019, 12:43pm UTC](https://forum.inductiveautomation.com/t/modbus-rtu-problem-in-8-0-4/28683/8 "2019-11-13T12:43:32Z")
It was fixed in 8.0.5. I’m not sure why a release note wasn’t generated because the ticket has one on it…