Use a robust asynchronous MQTT client

flake.lock

@@ -1,37 +1,23 @@
 {
   "nodes": {
-    "flake-utils": {
-      "locked": {
-        "lastModified": 1676283394,
-        "narHash": "sha256-XX2f9c3iySLCw54rJ/CZs+ZK6IQy7GXNY4nSOyu2QG4=",
-        "owner": "numtide",
-        "repo": "flake-utils",
-        "rev": "3db36a8b464d0c4532ba1c7dda728f4576d6d073",
-        "type": "github"
-      },
-      "original": {
-        "owner": "numtide",
-        "repo": "flake-utils",
-        "type": "github"
-      }
-    },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1677229269,
-        "narHash": "sha256-awE2w6oi9rzQ8qj1lwKEDm6qIA0a239fiB+AyPjXR2w=",
+        "lastModified": 1773046814,
+        "narHash": "sha256-3CEw64UyzEk5QjfbcXNIl4TfmIpa2oY+duuo6aiawcU=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "7d0ed7f2e5aea07ab22ccb338d27fbe347ed2f11",
+        "rev": "0c6c0dd2469abaa216599bb19bbf77a328af6564",
         "type": "github"
       },
       "original": {
-        "id": "nixpkgs",
-        "type": "indirect"
+        "owner": "NixOS",
+        "ref": "nixos-unstable-small",
+        "repo": "nixpkgs",
+        "type": "github"
       }
     },
     "root": {
       "inputs": {
-        "flake-utils": "flake-utils",
         "nixpkgs": "nixpkgs"
       }
     }

flake.nix

@@ -1,14 +1,25 @@
 {
-  description = "";
+  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable-small";
 
-  inputs.flake-utils.url = "github:numtide/flake-utils";
-
-  outputs = { self, nixpkgs, flake-utils }:
-    flake-utils.lib.eachDefaultSystem
-      (system:
-        let pkgs = nixpkgs.legacyPackages.${system}; in
+  outputs =
+    { self, nixpkgs, ... }:
+    let
+      system = "x86_64-linux";
+    in
     {
-          devShell = import ./shell.nix { inherit pkgs; };
-        }
-      );
+      devShells."${system}".default =
+        let
+          pkgs = import nixpkgs {
+            inherit system;
+          };
+        in
+        pkgs.mkShell {
+          packages = with pkgs; [
+            clang
+            platformio
+          ];
+
+          shellHook = "";
+        };
+    };
 }

include/config.h

@@ -1,8 +1,6 @@
 #ifndef CONFIG_H_
 #define CONFIG_H_
 
-#include "FS.h"
-#include "LittleFS.h"
 #include <ArduinoJson.h>
 
 typedef struct {
@@ -14,14 +12,13 @@ typedef struct {
     const char *topic;
     const char *device_id;
     int mqtt_port;
-  long sleep_time;
-  int connection_attempts;
+    unsigned long sleep_time;
 } Config;
 
-void initialize_config(Config *config, StaticJsonDocument<512> json);
+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 +1,10 @@
+#ifndef SENSOR_H_
+#define SENSOR_H_
+
+#include <DHT.h>
+
+void initialize_sensor(DHT &sensor);
+
+void read_values(DHT &sensor, float *data);
+
+#endif // SENSOR_H_

include/wlan.h

@@ -2,15 +2,28 @@
 #define WLAN_H
 
 #include "config.h"
-#include <ESP8266WiFi.h>
-#include <PubSubClient.h>
+#include <AsyncMqttClient.h>
+#include <Ticker.h>
+#include <WiFi.h>
+
+static AsyncMqttClient mqtt_client;
+static Ticker mqtt_connection_timer, wlan_connection_timer;
+extern Config *config;
+
+void initialize_wlan();
+
+void initialize_mqtt();
+
+void connect_wlan();
+
+void connect_mqtt();
+
+void wlan_connection_handler(WiFiEvent_t event);
+
+void on_mqtt_disconnection(AsyncMqttClientDisconnectReason reason);
 
-void initial_connection(const char *ssid, const char *psk);
-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 enter_deep_sleep(bool wifi_timeout, int sleep_time);
+
+void mqtt_transfer(float *data);
 
 #endif /* WLAN_H */

platformio.ini

@@ -9,12 +9,13 @@
 ; https://docs.platformio.org/page/projectconf.html
 
 [env:d1_mini]
-platform = espressif8266
-board = d1_mini
+platform = espressif32
+board = wemos_d1_mini32
 board_build.filesystem = littlefs
 framework = arduino
+monitor_filters = esp32_exception_decoder
 lib_deps =
   adafruit/DHT sensor library@^1.4.4
   adafruit/Adafruit Unified Sensor@^1.1.9
-  knolleary/PubSubClient@^2.8
-  bblanchon/ArduinoJson@^6.21.1
+  marvinroger/AsyncMqttClient@^0.9.0
+  bblanchon/ArduinoJson@^7.4.1

shell.nix

@@ -1,5 +0,0 @@
-{ pkgs ? import <nixpkgs> { } }:
-
-with pkgs;
-
-mkShell { buildInputs = [ platformio clang ]; }

src/config.cpp

@@ -1,6 +1,7 @@
 #include "config.h"
+#include "LittleFS.h"
 
-void initialize_config(Config *config, StaticJsonDocument<512> json) {
+void initialize_config(Config *config, JsonDocument json) {
     config->ssid = strdup(json["ssid"]);
     config->psk = strdup(json["psk"]);
     config->mqtt_host = strdup(json["mqtt_host"]);
@@ -9,8 +10,7 @@ void initialize_config(Config *config, StaticJsonDocument<512> 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->connection_attempts = json["connection_attempts"];
+    config->sleep_time = minutes_to_milliseconds(json["sleep_time"]);
 }
 
 bool load_config_file(const char *file_path, Config *config) {
@@ -19,7 +19,7 @@ bool load_config_file(const char *file_path, Config *config) {
     File config_file = LittleFS.open(file_path, "r");
     if (!config_file)
         return false;
-  StaticJsonDocument<512> json;
+    JsonDocument json;
     DeserializationError err = deserializeJson(json, config_file);
     if (err)
         return false;
@@ -27,4 +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

@@ -1,41 +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);
+
+    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);
+    unsigned long current_millis = millis();
+
+    if (current_millis - previous_millis >= config->sleep_time) {
+        previous_millis = current_millis;
+        read_values(dht, data);
+        mqtt_transfer(data);
     }
-  disconnect_mqtt(mqtt_client, config->topic);
-  free(config);
-  enter_deep_sleep(false, config->sleep_time);
 }

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(".");
+void connect_wlan() { WiFi.begin(config->ssid, config->psk); }
+
+void connect_mqtt() {
+    Serial.println("Connecting to MQTT");
+    mqtt_client.connect();
 }
+
+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");
-}
-
-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);
+        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;
+    JsonDocument 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;
 }
 
-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 =
+        mqtt_client.publish(config->topic, 2, true, buffer, payload_size);
+    if (response)
         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);
-}