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FB_INPUT_PUSHBUTTON_MQTT.md

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FB_INPUT_PUSHBUTTON_MQTT

MQTT Discovery

General

Reads out a digital input and sets a single, double or long output high for one cycle when one of those events has been detected on the configured input.

Block diagram

INPUT(S)

  • PB: digital input linked to the signal wire of a pushbutton.

OUTPUT(S)

  • SINGLE: output high for one clock cycle when a single push is detected on input PB.
  • DOUBLE: output high for one clock cycle when a double push is detected on input PB.
  • LONG: output high for one clock cycle when a long push is detected on input PB.
  • P_LONG: output becomes high when a long push is detected on input PB, remains high as long as PB remains high.

METHOD(S)

  • InitMQTT: enables MQTT events on the FB, an overview of the parameters:

    • MQTTPublishPrefix: datatype POINTER TO STRING, pointer to the MQTT publish prefix that should be used for publishing any messages/events for this FB. Suffix is automatically set to FB name.
    • pMqttPublishQueue: datatype POINTER TO FB_MqttPublishQueue, pointer to the MQTT queue to publish messages.

  • ConfigureFunctionBlock: configures the time parameter specifing the decoding time for long key press. Defaults to 400ms.

MQTT Event Behaviour

Requires method call InitMQTT to enable MQTT capabilities.

Event Description MQTT payload QoS Retain flag Published on startup
Pushbutton single press A single pushbutton press is detected on input PB. {"event_type": "SINGLE"} 2 FALSE no
Pushbutton double press A double pushbutton press is detected on input PB. {"event_type": "DOUBLE"} 2 FALSE no
Pushbutton long press A long pushbutton press is detected on input PB. {"event_type": "LONG"} 2 FALSE no

MQTT publish topic is a concatenation of the publish prefix variable and the function block name.

(*): MQTT publish topic is a concatenation of the publish prefix variable, the function block name and the name of the output.

Code example

  • variables initiation:
MQTTPushbuttonPrefix    :STRING(100) := 'Devices/PLC/House/Out/DigitalInputs/Pushbuttons/';
FB_DI_PB_001            :FB_INPUT_PUSHBUTTON_MQTT;
  • Init MQTT method call (called once during startup):
FB_DI_PB_001.InitMQTT(MQTTPublishPrefix:= ADR(MQTTPushbuttonPrefix),    (* pointer to string prefix for the MQTT publish topic *)
    pMQTTPublishQueue := ADR(MQTTVariables.fbMQTTPublishQueue)          (* pointer to MQTTPublishQueue to send a new MQTT event *)
);

The MQTT publish topic in this code example will be Devices/PLC/House/Out/DigitalInputs/Pushbuttons/FB_DI_PB_001 (MQTTPushbuttonPrefix variable + function block name).

  • reading digital input for events (cyclic):
FB_DI_PB_001(PB:= DI_001);
  • integration with FB_OUTPUT_SWITCH_MQTT:
FB_DO_SW_001(OUT=>  DO_001,                 (* couple the function block to the physical output *)
    PRIOHIGH:=      FALSE,                  (* brings the output high regardless of other input values *)
    PRIOLOW:=       FALSE,                  (* brings the output low regardless of other input values. NOTE: Priohigh overrules Priolow input *)
    TOGGLE:=        FB_DI_PB_001.SINGLE     (* for toggling the output *)	
);
  • MQTT discovery:
FB_DI_PB_001.InitMqttDiscovery(
	Name := 'pushbutton 001',			    (* The name show in Home Assistant frond-end*)
	Device := ADR(PLC_DEVICE),				(* The device show in Home Assistant *)
);

Home Assistant YAML

If MQTT discovery is not working for you, you can use the YAML code below in your MQTT events config:

mqtt:
  event:
  # To receive single/double/long events
  - name: "FB_DI_PB_001"
    state_topic: "Devices/PLC/House/Out/DigitalInputs/Pushbuttons/FB_DI_PB_001"
    event_types:
      - "SINGLE"
      - "DOUBLE"
      - "LONG"
    qos: 2    
    device_class: "button"
    availability_topic: "Devices/PLC/House/availability"
    payload_available: "online"
    payload_not_available: "offline"