Replace the MQTT client with a robust async option

data/example.json

@@ -7,6 +7,5 @@
   "mqtt_port": 1883,
   "mqtt_topic": "",
   "device_id": "",
-  "sleep_time": 30,
+  "sleep_time": 30
-  "connection_attempts": 60
 }

include/config.h

@@ -12,14 +12,13 @@ typedef struct {
     const char *topic;
     const char *device_id;
     int mqtt_port;
-    long sleep_time;
+    unsigned long sleep_time;
-    int connection_attempts;
 } Config;
 
 void initialize_config(Config *config, JsonDocument json);
 
 bool load_config_file(const char *file_path, Config *config);
 
-long minutes_to_microseconds(int minutes);
+long minutes_to_milliseconds(int minutes);
 
 #endif // CONFIG_H_

include/sensor.h

@@ -0,0 +1,14 @@
+#ifndef SENSOR_H_
+#define SENSOR_H_
+
+#include <SensirionI2cScd4x.h>
+
+void handle_error(int code, char *msg);
+
+void initialize_sensor(SensirionI2cScd4x &sensor, int error_code,
+                       char *error_msg);
+
+void read_values(SensirionI2cScd4x &sensor, float *data, int error_code,
+                 char *error_msg);
+
+#endif // SENSOR_H_

include/wlan.h

@@ -2,14 +2,33 @@
 #define WLAN_H
 
 #include "config.h"
-#include <PubSubClient.h>
+#include <AsyncMqttClient.h>
+#include <ESP8266WiFi.h>
+#include <Ticker.h>
+
+static AsyncMqttClient mqtt_client;
+static Ticker mqtt_connection_timer, wlan_connection_timer;
+static WiFiEventHandler connection_handler, disconnection_handler;
+extern Config *config;
+
+void initialize_wlan();
+
+void initialize_mqtt();
+
+void connect_wlan();
+
+void connect_mqtt();
+
+void on_wlan_connection(const WiFiEventStationModeGotIP &event);
+
+void on_wlan_disconnection(const WiFiEventStationModeDisconnected &event);
+
+void on_mqtt_connection(bool session);
+
+void on_mqtt_disconnection(AsyncMqttClientDisconnectReason reason);
 
-void initial_connection(const char *ssid, const char *psk,
-                        const char *hostname);
-void connect_wlan(Config *config);
-void connect_mqtt(PubSubClient &client, Config *config);
-void disconnect_mqtt(PubSubClient &client, const char *topic);
 size_t construct_json(float *data, char *buffer, int buffer_size);
-void mqtt_transfer(PubSubClient &client, Config *config, float *data);
+
+void mqtt_transfer(float *data);
 
 #endif /* WLAN_H */

platformio.ini

@@ -16,6 +16,6 @@ framework = arduino
 monitor_filters = esp8266_exception_decoder
 lib_deps =
   sensirion/Sensirion I2C SCD4x@^1.1.0
-  knolleary/PubSubClient@^2.8
+  marvinroger/AsyncMqttClient@^0.9.0
   bblanchon/ArduinoJson@^7.4.1
 

src/config.cpp

@@ -10,8 +10,7 @@ void initialize_config(Config *config, JsonDocument json) {
     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->sleep_time = minutes_to_milliseconds(json["sleep_time"]);
-    config->connection_attempts = json["connection_attempts"];
 }
 
 bool load_config_file(const char *file_path, Config *config) {
@@ -28,4 +27,4 @@ bool load_config_file(const char *file_path, Config *config) {
     return true;
 }
 
-long minutes_to_microseconds(int minutes) { return (minutes * 6e7); }
+long minutes_to_milliseconds(int minutes) { return (minutes * 6e4); }

src/main.cpp

@@ -1,63 +1,37 @@
+#include "sensor.h"
 #include "wlan.h"
 #include <Arduino.h>
-#include <ESP8266WiFi.h>
-#include <PubSubClient.h>
-#include <SensirionI2cScd4x.h>
-#include <Wire.h>
 
 SensirionI2cScd4x sensor;
 
-int error;
+int error_code;
-static char errorMessage[64];
+char error_msg[64];
 
 const char *config_file_path = "/config.json";
-long inactivity_delay;
 Config *config;
-WiFiClient wifi_client;
-PubSubClient mqtt_client(wifi_client);
 
-int check_error(int error) {
+float data[3];
-    if (error) {
+unsigned long previous_millis = 0;
-        Serial.println("Error while initializing sensor");
-        errorToString(error, errorMessage, sizeof errorMessage);
-        return 1;
-    }
-    return 0;
-}
 
 void setup() {
     Serial.begin(9600);
-    Wire.begin();
+    config = (Config *)malloc(sizeof(Config));
-    sensor.begin(Wire, SCD41_I2C_ADDR_62);
+
-    error = sensor.wakeUp();
+    if (!load_config_file(config_file_path, config))
-    error = sensor.stopPeriodicMeasurement();
+        Serial.println("ERROR: The config file could not be loaded");
-    error = sensor.reinit();
+
-    error = sensor.startPeriodicMeasurement();
+    initialize_wlan();
-    inactivity_delay = 60000;
+    initialize_mqtt();
+    connect_wlan();
+    initialize_sensor(sensor, error_code, error_msg);
 }
 
 void loop() {
-    uint16_t co2_concentration = 0.0;
+    unsigned long current_millis = millis();
-    float temperature = 0.0;
-    float humidity = 0.0;
-    bool data_available = false;
 
-    error = sensor.getDataReadyStatus(data_available);
+    if (current_millis - previous_millis >= config->sleep_time) {
-    error = sensor.readMeasurement(co2_concentration, temperature, humidity);
+        previous_millis = current_millis;
-
+        read_values(sensor, data, error_code, error_msg);
-    if (data_available) {
+        mqtt_transfer(data);
-        Serial.print("CO2 concentration [ppm]: ");
-        Serial.print(co2_concentration);
-        Serial.println();
-        Serial.print("Temperature [°C]: ");
-        Serial.print(temperature);
-        Serial.println();
-        Serial.print("Relative Humidity [RH]: ");
-        Serial.print(humidity);
-        Serial.println();
-    } else {
-        Serial.println(".");
     }
-
-    delay(inactivity_delay);
 }

src/sensor.cpp

@@ -0,0 +1,49 @@
+#include "sensor.h"
+#include <Wire.h>
+
+// TODO Trigger a reset when an error occurs
+void handle_error(int code, char *msg) {
+    if (code) {
+        errorToString(code, msg, sizeof msg);
+        exit(1);
+    }
+}
+
+void initialize_sensor(SensirionI2cScd4x &sensor, int error_code,
+                       char *error_msg) {
+    Wire.begin();
+    sensor.begin(Wire, SCD41_I2C_ADDR_62);
+    Serial.println("Starting sensor initialization");
+
+    error_code = sensor.wakeUp();
+    handle_error(error_code, error_msg);
+    error_code = sensor.stopPeriodicMeasurement();
+    handle_error(error_code, error_msg);
+    error_code = sensor.reinit();
+    handle_error(error_code, error_msg);
+    error_code = sensor.startPeriodicMeasurement();
+    handle_error(error_code, error_msg);
+
+    Serial.println("The sensor was initialized properly");
+};
+
+void read_values(SensirionI2cScd4x &sensor, float *data, int error_code,
+                 char *error_msg) {
+    bool data_available = false;
+    short unsigned int co2_concentration = 0.0;
+
+    error_code = sensor.getDataReadyStatus(data_available);
+    handle_error(error_code, error_msg);
+
+    while (!data_available) {
+        delay(100);
+        error_code = sensor.getDataReadyStatus(data_available);
+        handle_error(error_code, error_msg);
+    }
+
+    Serial.println("Data fetched from the sensor");
+
+    error_code = sensor.readMeasurement(co2_concentration, data[1], data[2]);
+    data[0] = co2_concentration;
+    handle_error(error_code, error_msg);
+}

src/wlan.cpp

@@ -1,53 +1,64 @@
 #include "wlan.h"
-#include <ESP8266WiFi.h>
 
-void initial_connection(const char *ssid, const char *psk,
+void initialize_wlan() {
-                        const char *hostname) {
+    connection_handler = WiFi.onStationModeGotIP(on_wlan_connection);
-    WiFi.hostname(hostname);
+    disconnection_handler =
-    WiFi.begin(ssid, psk);
+        WiFi.onStationModeDisconnected(on_wlan_disconnection);
-    WiFi.persistent(true);
-    WiFi.setAutoConnect(true);
-    WiFi.setAutoReconnect(true);
 }
 
-void connect_wlan(Config *config) {
+void initialize_mqtt() {
-    if (WiFi.SSID() != config->ssid)
+    mqtt_client.onConnect(on_mqtt_connection);
-        initial_connection(config->ssid, config->psk, config->device_id);
+    mqtt_client.onDisconnect(on_mqtt_disconnection);
-    while (WiFi.status() != WL_CONNECTED) {
+    mqtt_client.setServer(config->mqtt_host, config->mqtt_port);
-        delay(1000);
+    mqtt_client.setCredentials(config->mqtt_user, config->mqtt_password);
-        Serial.print(".");
+    Serial.println("MQTT initialization complete");
-    }
+}
+
+void connect_wlan() { WiFi.begin(config->ssid, config->psk); }
+
+void connect_mqtt() {
+    Serial.println("Connecting to MQTT");
+    mqtt_client.connect();
+}
+
+void on_wlan_connection(const WiFiEventStationModeGotIP &event) {
     Serial.println("WiFi connected");
+    connect_mqtt();
 }
 
-void connect_mqtt(PubSubClient &client, Config *config) {
+void on_wlan_disconnection(const WiFiEventStationModeDisconnected &event) {
-    if (!client.connected())
+    Serial.println("WiFi disconnected");
-        client.setServer(config->mqtt_host, config->mqtt_port);
+    mqtt_connection_timer.detach();
-    if (client.connect(config->device_id, config->mqtt_user,
+    wlan_connection_timer.once(2, connect_wlan);
-                       config->mqtt_password)) {
+}
-        Serial.println("MQTT connected");
+
-        client.subscribe(config->topic);
+void on_mqtt_connection(bool session) {
+    Serial.println("MQTT connected");
+    mqtt_client.subscribe(config->topic, 2);
+};
+
+void on_mqtt_disconnection(AsyncMqttClientDisconnectReason reason) {
+    Serial.println("MQTT disconnected");
+
+    if (WiFi.isConnected()) {
+        mqtt_connection_timer.once(2, connect_mqtt);
     }
 }
 
-void disconnect_mqtt(PubSubClient &client, const char *topic) {
-    Serial.println("Disconnecting MQTT");
-    client.unsubscribe(topic);
-    client.disconnect();
-}
-
 size_t construct_json(float *data, char *buffer, int buffer_size) {
     JsonDocument json;
-    json["temperature"] = data[0];
+    json["co2_concentration"] = data[0];
-    json["humidity"] = data[1];
+    json["temperature"] = data[1];
+    json["humidity"] = data[2];
     size_t payload_size = serializeJson(json, buffer, buffer_size);
     return payload_size;
 }
 
-void mqtt_transfer(PubSubClient &client, Config *config, float *data) {
+void mqtt_transfer(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);
+    uint16_t response =
-    Serial.println("Data transferred successfully");
+        mqtt_client.publish(config->topic, 2, true, buffer, payload_size);
+    if (response)
+        Serial.println("Data transferred successfully");
 }