New usermod: MQTT switches.

This user mod adds a function to toggle output pins via MQTT.

usermods/mqtt_switch_v2/README.md

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+# MQTT controllable switches
+This usermod allows controlling switches (e.g. relays) via MQTT.
+
+## Usermod installation
+
+1. Copy the file `usermod_mqtt_switch.h` to the `wled00` directory.
+2. Register the usermod by adding `#include "usermod_mqtt_switch.h"` in the top and `registerUsermod(new UsermodMqttSwitch());` in the bottom of `usermods_list.cpp`.
+
+
+Example `usermods_list.cpp`:
+
+```
+#include "wled.h"
+#include "usermod_mqtt_switch.h"
+
+void registerUsermods()
+{
+  usermods.add(new UsermodMqttSwitch());
+}
+```
+
+## Define pins
+Add a define for MQTTSWITCHPINS to platformio_override.ini.
+The following example defines 3 switches connected to the GPIO pins 13, 0 and 2:
+
+```
+[env:livingroom]
+board = esp12e
+platform = ${common.platform_wled_default}
+board_build.ldscript = ${common.ldscript_4m1m}
+build_flags = ${common.build_flags_esp8266} 
+   -D LEDPIN=3
+   -D BTNPIN=4
+   -D RLYPIN=12
+   -D RLYMDE=1
+   -D STATUSPIN=15
+   -D MQTTSWITCHPINS="13, 0, 2"
+```
+   
+## MQTT topics
+This usermod listens on `[mqttDeviceTopic]/switch/0/set` (where 0 is replaced with the index of the switch) for commands. Anything starting with `ON` turns on the switch, everything else turns it off.
+Feedback about the current state is provided at `[mqttDeviceTopic]/switch/0/state`.
+
+### Home Assistant auto-discovery
+Auto-discovery information is automatically published and you shoudn't have to do anything to register the switches in Home Assistant.
+ 

usermods/mqtt_switch_v2/usermod_mqtt_switch.h

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+#pragma once
+
+#include "wled.h"
+#ifndef WLED_ENABLE_MQTT
+#error "This user mod requires MQTT to be enabled."
+#endif
+
+#ifndef MQTTSWITCHPINS
+#define MQTTSWITCHPINS 12, 0, 2
+//#error "Please define MQTTSWITCHPINS in platformio_override.ini. e.g. -D MQTTSWITCHPINS="12, 0, 2" "
+#endif
+
+
+static const uint8_t switchPins[] = {MQTTSWITCHPINS};
+//This is a hack to get the number of pins defined by the user
+#define NUM_SWITCH_PINS (sizeof(switchPins))
+
+class UsermodMqttSwitch: public Usermod
+{
+private:
+    bool mqttInitialized;
+    bool switchState[NUM_SWITCH_PINS];
+
+public:
+    UsermodMqttSwitch() :
+            mqttInitialized(false)
+    {
+    }
+
+    void setup()
+    {
+        for (int pinNr = 0; pinNr < NUM_SWITCH_PINS; pinNr++) {
+            pinMode(switchPins[pinNr], OUTPUT);
+            setState(pinNr, false);
+        }
+    }
+
+    void loop()
+    {
+        if (!mqttInitialized) {
+            mqttInit();
+            return; // Try again in next loop iteration
+        }
+    }
+
+    void mqttInit()
+    {
+        if (!mqtt)
+            return;
+        mqtt->onMessage(
+                std::bind(&UsermodMqttSwitch::onMqttMessage, this, std::placeholders::_1, std::placeholders::_2, std::placeholders::_3, std::placeholders::_4,
+                          std::placeholders::_5, std::placeholders::_6));
+        mqtt->onConnect(std::bind(&UsermodMqttSwitch::onMqttConnect, this, std::placeholders::_1));
+        mqttInitialized = true;
+    }
+
+    void onMqttConnect(bool sessionPresent);
+
+    void onMqttMessage(char *topic, char *payload, AsyncMqttClientMessageProperties properties, size_t len, size_t index, size_t total);
+    void updateState(uint8_t pinNr);
+
+    void setState(uint8_t pinNr, bool active)
+    {
+        if (pinNr > NUM_SWITCH_PINS)
+            return;
+        switchState[pinNr] = active;
+        digitalWrite((char) switchPins[pinNr], (char) active);
+        updateState(pinNr);
+    }
+};
+
+inline void UsermodMqttSwitch::onMqttConnect(bool sessionPresent)
+{
+    if (mqttDeviceTopic[0] == 0)
+        return;
+
+    for (int pinNr = 0; pinNr < NUM_SWITCH_PINS; pinNr++) {
+        char buf[128];
+        StaticJsonDocument<1024> json;
+        sprintf(buf, "%s Switch %d", serverDescription, pinNr + 1);
+        json[F("name")] = buf;
+
+        sprintf(buf, "%s/switch/%d", mqttDeviceTopic, pinNr);
+        json["~"] = buf;
+        strcat(buf, "/set");
+        mqtt->subscribe(buf, 0);
+
+        json[F("stat_t")] = "~/state";
+        json[F("cmd_t")] = "~/set";
+        json[F("pl_off")] = F("OFF");
+        json[F("pl_on")] = F("ON");
+
+        char uid[16];
+        sprintf(uid, "%s_sw%d", escapedMac.c_str(), pinNr);
+        json[F("unique_id")] = uid;
+
+        strcpy(buf, mqttDeviceTopic);
+        strcat(buf, "/status");
+        json[F("avty_t")] = buf;
+        json[F("pl_avail")] = F("online");
+        json[F("pl_not_avail")] = F("offline");
+        //TODO: dev
+        sprintf(buf, "homeassistant/switch/%s/config", uid);
+        char json_str[1024];
+        size_t payload_size = serializeJson(json, json_str);
+        mqtt->publish(buf, 0, true, json_str, payload_size);
+        updateState(pinNr);
+    }
+}
+
+inline void UsermodMqttSwitch::onMqttMessage(char *topic, char *payload, AsyncMqttClientMessageProperties properties, size_t len, size_t index, size_t total)
+{
+    //Note: Payload is not necessarily null terminated. Check "len" instead.
+    for (int pinNr = 0; pinNr < NUM_SWITCH_PINS; pinNr++) {
+        char buf[64];
+        sprintf(buf, "%s/switch/%d/set", mqttDeviceTopic, pinNr);
+        if (strcmp(topic, buf) == 0) {
+            //Any string starting with "ON" is interpreted as ON, everything else as OFF
+            setState(pinNr, len >= 2 && payload[0] == 'O' && payload[1] == 'N');
+            break;
+        }
+    }
+}
+
+inline void UsermodMqttSwitch::updateState(uint8_t pinNr)
+{
+    if (!mqttInitialized)
+        return;
+
+    if (pinNr > NUM_SWITCH_PINS)
+        return;
+
+    char buf[64];
+    sprintf(buf, "%s/switch/%d/state", mqttDeviceTopic, pinNr);
+    if (switchState[pinNr]) {
+        mqtt->publish(buf, 0, false, "ON");
+    } else {
+        mqtt->publish(buf, 0, false, "OFF");
+    }
+}