FB_ALYC_MqttStream

This function block represents an Analytics MQTT stream. The connection to a stream can be established using the ObjectId as an input variable. The requirement is an existing stream, e.g. created in the System Manager under the Data Logger node in the project tree. The stream can be controlled using the Start/Stop methods and reconfigured using Reconfigure. A structure of the type ST_ALYC_MqttStreamConfig containing the new configuration parameters is transferred to the method for this purpose. During reconfiguration, starting from the OP state, the TcCom states SAFEOP, PREOP, SAFEOP, OP are run through in this order. Since all states below SAFEOP no longer run in real-time mode, but the remaining TwinCAT runtime does, the reconfiguration must take place asynchronously to the task cycle, whereby the Reconfig method should be called cyclically as long as the OP state is not reached again. The properties bConnected, bStarted etc. provide information about the current state of the stream. Errors can be recorded via the bError output and the corresponding ipResultMessage.

Definition:

FUNCTION_BLOCK FB_ALYC_MqttStream
VAR_INPUT
     {attribute 'tcinitsymbol'}
     nObjectID : OTCID := 0;
END_VAR
VAR_OUTPUT
     bInitialized : BOOL := FALSE;
     bError : BOOL := FALSE;
     ipResultMessage : I_TcMessage := fbResult;
     eReconfigState : E_ALYC_ReconfigState := E_ALYC_ReconfigState.DONE;
END_VAR

Inputs

Name	Type	Description
nObjectID	OTCID	TcCom-Object ID of the referenced stream. This can be initialized under the 'Init symbols' tab of the corresponding PLC instance node in the System Manager project tree.

Outputs

Name	Type	Description
bInitialized	BOOL	TRUE if the function block is initialized and can be used. Initialization takes place automatically after TwinCAT is set to run mode.
bError	BOOL	TRUE if an error has occurred.
ipResultMessage	I_TcMessage	Message EventLogger
eReconfigState	E_ALYC_ReconfigState	The state of the state machine during reconfiguration.

Methods

Name	Return type	Description
Reconfigure	BOOL	Reconfigure the stream. Parameter: ST_ALYC_MqttStreamConfig. TRUE if successful.
Start	BOOL	Start the stream. TRUE if successful.
Stop	BOOL	Stop the stream. TRUE if successful.

Properties

Name	Type	Direction	Description
bConnected	BOOL	get	TRUE if MQTT connection exists.
bStarted	BOOL	get	TRUE if stream started.
nDataSize	UDINT	get	Sample data size
nSamplesIssued	ULINT	get	Number of samples that have been written.
nSamplesLost	ULINT	get	Number of discarded samples.
tCycleTime	LTIME	get	Cycle time in ns
nCompDataSaving	DINT	get	Percentage of data volume saved compared to the uncompressed alternative. If negative, there is additional work instead of data savings.