MqttSubscribe (FB)

FUNCTION_BLOCK MqttSubscribe EXTENDS AbbETrig

subscribe to a topic on an already established connection to an MQTT broker

Attributes:

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InOut:

Scope	Name	Type	Initial	Comment	Inherited from
Input	Execute	BOOL	FALSE	A rising edge starts the operation, the output Busy goes to TRUE. In the first cycle all other inputs are read and stored, afterwards they are ignored. A falling edge does not stop the operation. After Done = TRUE or Error = TRUE and Execute = FALSE all outputs will be reset.	AbbETrig
Output	Done	BOOL	FALSE	Operation is completed without error (while outputs Busy and Error are FALSE). This output is TRUE for at least one cycle or until Execute is set to FALSE	AbbETrig
	Busy	BOOL	FALSE	Operation is running (while outputs Done and Error are FALSE)	AbbETrig
	Error	BOOL	FALSE	Operation is stopped with error (while outputs Busy and Done are FALSE). This output is TRUE for at least one cycle or until Execute is set to FALSE. The output ErrorID gives more details about the error.	AbbETrig
Input	Conn	POINTER TO MQTT_CONNECTION	0	Pointer to valid connection struct created by MqttConnect
	Topic	STRING(Constants.MQTT_MAX_TOPIC_LEN)	Defaults.MQTT_DEFAULT_EMPTY	Topic name as a string. See the description at the top. For further information see the MQTT specification.
	MaxQos	MQTT_QOS	MQTT_QOS.QOS_0	Signals the server which is the highest QoS level which can be handled. Can be reduced to relieve the client from high network load.
Output	ErrorID	ERROR_ID	ERROR_ID.MQTT_ERR_NO_ERROR	Error code description

• MqttSubscribe.A_StartAction (METH)
  • StartAction
  • Called: In the first invocation
• MqttSubscribe.B_CyclicAction (METH)
  • CyclicAction
• MqttSubscribe.C_CleaningAction (METH)
  • CleaningAction
  • Return: —
• MqttSubscribe.D_ResetAction (METH)
  • ResetAction
  • Called: After DONE or ERROR cycle is finished