## FB_INPUT_PUSHBUTTON_MQTT
![MQTT Discovery](https://img.shields.io/badge/MQTT%20Discovery-brightgreen)

### **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**

<img src="../_img/FB_INPUT_PUSHBUTTON_MQTT.svg" width="350">

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.
    - `pMqttCallbackCollector`: datatype _POINTER TO MQTT.CallbackCollector, pointer to the MQTT callback collector to receive subscribe messages.

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

### **MQTT publish behavior**
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](../AdditionalFunctionality/MQTT_Discovery.md) is not working for you, you can use the YAML code below in your [MQTT events](https://www.home-assistant.io/integrations/event.mqtt/) config:

```YAML
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"
```