Use a robust asynchronous MQTT client

src/config.cpp

@@ -1,30 +1,30 @@
 #include "config.h"
+#include "LittleFS.h"
 
-void initialize_config(Config *config, StaticJsonDocument<512> json) {
-  config->ssid = strdup(json["ssid"]);
-  config->psk = strdup(json["psk"]);
-  config->mqtt_host = strdup(json["mqtt_host"]);
-  config->mqtt_user = strdup(json["mqtt_user"]);
-  config->mqtt_password = strdup(json["mqtt_password"]);
-  config->topic = strdup(json["mqtt_topic"]);
-  config->device_id = strdup(json["device_id"]);
-  config->mqtt_port = json["mqtt_port"];
-  config->sleep_time = minutes_to_microseconds(json["sleep_time"]);
-  config->connection_attempts = json["connection_attempts"];
+void initialize_config(Config *config, JsonDocument json) {
+    config->ssid = strdup(json["ssid"]);
+    config->psk = strdup(json["psk"]);
+    config->mqtt_host = strdup(json["mqtt_host"]);
+    config->mqtt_user = strdup(json["mqtt_user"]);
+    config->mqtt_password = strdup(json["mqtt_password"]);
+    config->topic = strdup(json["mqtt_topic"]);
+    config->device_id = strdup(json["device_id"]);
+    config->mqtt_port = json["mqtt_port"];
+    config->sleep_time = minutes_to_milliseconds(json["sleep_time"]);
 }
 
 bool load_config_file(const char *file_path, Config *config) {
-  if (!LittleFS.begin())
-    return false;
-  File config_file = LittleFS.open(file_path, "r");
-  if (!config_file)
-    return false;
-  StaticJsonDocument<512> json;
-  DeserializationError err = deserializeJson(json, config_file);
-  if (err)
-    return false;
-  initialize_config(config, json);
-  return true;
+    if (!LittleFS.begin())
+        return false;
+    File config_file = LittleFS.open(file_path, "r");
+    if (!config_file)
+        return false;
+    JsonDocument json;
+    DeserializationError err = deserializeJson(json, config_file);
+    if (err)
+        return false;
+    initialize_config(config, json);
+    return true;
 }
 
-long minutes_to_microseconds(int minutes) { return (minutes * 6e7); }
+long minutes_to_milliseconds(int minutes) { return (minutes * 6e4); }

src/main.cpp

@@ -1,41 +1,36 @@
 #include "config.h"
+#include "sensor.h"
 #include "wlan.h"
 #include <Arduino.h>
 #include <DHT.h>
 
-#define DHTTYPE DHT22
-#define DHTPIN 4
-DHT dht(DHTPIN, DHTTYPE);
+DHT dht(4, DHT22);
 
-const int fc28_pin = A0;
 const char *config_file_path = "/config.json";
 Config *config;
-WiFiClient wifi_client;
-PubSubClient mqtt_client(wifi_client);
 
-bool check_valid_value(float value) {
-  return (!isnan(value) && value >= 0 && value <= 100);
-}
+float data[2];
+unsigned long previous_millis = 0;
 
 void setup() {
-  Serial.begin(9600);
-  dht.begin();
-  config = (Config *)malloc(sizeof(Config));
-  if (!load_config_file(config_file_path, config))
-    Serial.println("ERROR: The config file could not be loaded");
-  connect_wlan(config);
+    Serial.begin(9600);
+    config = (Config *)malloc(sizeof(Config));
+
+    if (!load_config_file(config_file_path, config))
+        Serial.println("ERROR: The config file could not be loaded");
+
+    initialize_wlan();
+    initialize_mqtt();
+    connect_wlan();
+    initialize_sensor(dht);
 }
 
 void loop() {
-  float temperature = dht.readTemperature();
-  float humidity = dht.readHumidity();
-  int analog_val = analogRead(fc28_pin);
-  int soil_percentage = map(analog_val, 0, 1023, 0, 100);
-  float data[3] = {temperature, humidity, static_cast<float>(soil_percentage)};
-  if (check_valid_value(temperature) && check_valid_value(humidity)) {
-    mqtt_transfer(mqtt_client, config, data);
-  }
-  disconnect_mqtt(mqtt_client, config->topic);
-  free(config);
-  enter_deep_sleep(false, config->sleep_time);
+    unsigned long current_millis = millis();
+
+    if (current_millis - previous_millis >= config->sleep_time) {
+        previous_millis = current_millis;
+        read_values(dht, data);
+        mqtt_transfer(data);
+    }
 }

src/sensor.cpp

@@ -0,0 +1,13 @@
+#include "sensor.h"
+
+void initialize_sensor(DHT &sensor) { sensor.begin(); }
+
+void read_values(DHT &sensor, float *data) {
+    float temperature = sensor.readTemperature();
+    float humidity = sensor.readHumidity();
+
+    Serial.println("Data fetched from the sensor");
+
+    data[0] = temperature;
+    data[1] = humidity;
+}

src/wlan.cpp

@@ -1,63 +1,57 @@
 #include "wlan.h"
-#include <ArduinoJson.h>
 
-void initial_connection(const char *ssid, const char *psk) {
-  WiFi.begin(ssid, psk);
-  WiFi.persistent(true);
-  WiFi.setAutoConnect(true);
-  WiFi.setAutoReconnect(true);
+void initialize_wlan() { WiFi.onEvent(wlan_connection_handler); }
+
+void initialize_mqtt() {
+    mqtt_client.onDisconnect(on_mqtt_disconnection);
+    mqtt_client.setServer(config->mqtt_host, config->mqtt_port);
+    mqtt_client.setCredentials(config->mqtt_user, config->mqtt_password);
+    Serial.println("MQTT initialization complete");
 }
 
-void connect_wlan(Config *config) {
-  if (WiFi.SSID() != config->ssid)
-    initial_connection(config->ssid, config->psk);
-  int retries = 0;
-  while (WiFi.status() != WL_CONNECTED) {
-    if (retries == config->connection_attempts)
-      enter_deep_sleep(true, config->sleep_time);
-    retries++;
-    delay(1000);
-    Serial.print(".");
-  }
-  Serial.println("WiFi connected");
+void connect_wlan() { WiFi.begin(config->ssid, config->psk); }
+
+void connect_mqtt() {
+    Serial.println("Connecting to MQTT");
+    mqtt_client.connect();
 }
 
-void connect_mqtt(PubSubClient &client, Config *config) {
-  if (!client.connected())
-    client.setServer(config->mqtt_host, config->mqtt_port);
-  if (client.connect(config->device_id, config->mqtt_user,
-                     config->mqtt_password)) {
-    Serial.println("MQTT connected");
-    client.subscribe(config->topic);
-  }
+void wlan_connection_handler(WiFiEvent_t event) {
+    Serial.printf("[WiFi-event] event: %d\n", event);
+    switch (event) {
+    case SYSTEM_EVENT_STA_GOT_IP:
+        Serial.println("WiFi connected");
+        connect_mqtt();
+        break;
+    case SYSTEM_EVENT_STA_DISCONNECTED:
+        Serial.println("WiFi disconnected");
+        mqtt_connection_timer.detach();
+        wlan_connection_timer.once(2, connect_wlan);
+        break;
+    }
 }
 
-void disconnect_mqtt(PubSubClient &client, const char *topic) {
-  Serial.println("Disconnecting MQTT");
-  client.unsubscribe(topic);
-  client.disconnect();
+void on_mqtt_disconnection(AsyncMqttClientDisconnectReason reason) {
+    Serial.println("MQTT disconnected");
+
+    if (WiFi.isConnected()) {
+        mqtt_connection_timer.once(2, connect_mqtt);
+    }
 }
 
 size_t construct_json(float *data, char *buffer, int buffer_size) {
-  StaticJsonDocument<100> json;
-  json["temperature"] = data[0];
-  json["humidity"] = data[1];
-  json["soil_humidity"] = data[2];
-  size_t payload_size = serializeJson(json, buffer, buffer_size);
-  return payload_size;
+    JsonDocument json;
+    json["temperature"] = data[0];
+    json["humidity"] = data[1];
+    size_t payload_size = serializeJson(json, buffer, buffer_size);
+    return payload_size;
 }
 
-void mqtt_transfer(PubSubClient &client, Config *config, float *data) {
-  char buffer[100];
-  connect_mqtt(client, config);
-  size_t payload_size = construct_json(data, buffer, 100);
-  client.publish(config->topic, buffer, payload_size);
-  Serial.println("Data transferred successfully");
-}
-
-void enter_deep_sleep(bool wifi_timeout, int sleep_time) {
-  Serial.println("Entering deep sleep");
-  if (wifi_timeout)
-    WiFi.disconnect();
-  ESP.deepSleep(sleep_time, WAKE_RF_DEFAULT);
+void mqtt_transfer(float *data) {
+    char buffer[100];
+    size_t payload_size = construct_json(data, buffer, 100);
+    uint16_t response =
+        mqtt_client.publish(config->topic, 2, true, buffer, payload_size);
+    if (response)
+        Serial.println("Data transferred successfully");
 }