FB_INPUT_BINARYSENSOR_MQTT.md

FB_INPUT_BINARYSENSOR_MQTT

General

Binary sensors gather information about the state of devices which have a "digital" return value (either 1 or 0). These can be switches, contacts, pins, etc. These sensors only have two states: 0/off/low/closed/false and 1/on/high/open/true

Block diagram

INPUT(S)

• BS: digital input linked to the signal wire of the binary sensor.

OUTPUT(S)

• Q: follows the input BS but debounced.
• EVENT: output high for one clock cycle when any event occurs on debounced input BS.
• EVENT_R: output high for one clock cycle when a rising edge is detected on debounced input BS.
• EVENT_F: output high for one clock cycle when a falling edge is detected on debounced input BS.

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 behaviour of output Q using the parameters below:

  • T_TurnOffDelay: duration of the turn off delay added on output Q to prevent rapid ON/OFF behaviour on the output caused by a fast switching sensor on the digital input. Defaults to 0 seconds, can be extremely usefull when connecting a motion sensor the the PLC.

MQTT Event Behaviour

Requires method call InitMQTT to enable MQTT capabilities.

Event	Description	MQTT payload	QoS	Retain flag	Published on startup
input changes: BS	A change is detected on input BS. (*)	ON/OFF	2	TRUE	yes

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

Code example

• variables initiation:

MQTTBinarySensorPrefix  :STRING(100) := 'Devices/PLC/House/Out/DigitalInputs/BinarySensors/';
FB_DI_BS_001            :FB_INPUT_BINARYSENSOR_MQTT;

• Init MQTT method call (called once during startup):

FB_INPUT_BINARYSENSOR_MQTT.InitMQTT(MQTTPublishPrefix:= ADR(MQTTBinarySensorPrefix),    (* 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/BinarySensors/FB_DI_BS_001 (MQTTBinarySensorPrefix variable + function block name).

• Configuration of the function block with a 5 second turn off delay on the output (called once during startup):

FB_INPUT_BINARYSENSOR_MQTT.ConfigureFunctionBlock(T_TurnOffDelay:= T#5S);         (* time to delay the negative edge on output Q *)

• reading digital input for events (cyclic):

FB_DI_BS_001(BS:= DI_001);

• integration with FB_OUTPUT_BINARY_MQTT:

FB_DO_SW_001(OUT=>  DO_001,                 (* couple the function block to the physical output *)
    PRIO_HIGH:=     FALSE,                  (* brings the output high regardless of other input values *)
    PRIO_LOW:=      FALSE,                  (* brings the output low regardless of other input values. NOTE: Priohigh overrules Priolow input *)
    TOGGLE:=        FB_DI_BS_001.EVENT      (* for toggling the output *)	
);

• MQTT discovery:

FB_DI_BS_001.InitMqttDiscovery(
	Name := 'Binary sensor 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 binary sensor config:

mqtt:
  binary_sensor:
  - name: "FB_DI_BS_001"
    state_topic: "Devices/PLC/House/Out/DigitalInputs/BinarySensors/FB_DI_BS_001"
    qos: 2  
    payload_on: "ON"
    payload_off: "OFF"
    availability_topic: "Devices/PLC/House/availability"
    payload_available: "online"
    payload_not_available: "offline"