Update README

.clangd

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+CompileFlags:
+  Remove: [-mlongcalls, -free, -mtext-section-literals, -fipa-pta]

.gitignore

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 .pio
+data/config.json

README.org

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 * Homeostasis
 
-Temperature, air humidity and soil humidity sensor that communicates via MQTT. The project is implemented using a Wemos D1 mini board with the following addons:
+Temperature, air humidity and soil humidity sensor that communicates via MQTT. The project is implemented using a Wemos D1 mini board with the following components:
 
-- DHT11
-- Soil hygrometer sensor
+- DHT22 temperature and humidity sensor
+- FC-28 soil hygrometer sensor
 - Battery shield
 - 3.7V 1000mAh Lithium battery
 
+The sensor captures the data every 15 minutes and sends it to a MQTT broker and then enters deep sleep, it is important to save power as the device runs off a battery.
+
+#+ATTR_HTML: :width 60%
+[[./result.png]]
+
 ** Pinout of the board
 
-#+ATTR_HTML: :width 50%
+#+ATTR_HTML: :width 40%
 [[./pinout.png]]
+** Dependencies
+- [[https://github.com/adafruit/DHT-sensor-library][Adafruit DHT sensor library]]
+- [[https://github.com/adafruit/Adafruit_Sensor][Adafruit Unified Sensor Driver]]
+- [[https://github.com/knolleary/pubsubclient][PubSubClient]]
+- [[https://github.com/bblanchon/ArduinoJson][ArduinoJSON]]
+** Deployment
+
+The software uses the Arduino framework and the development environment of [[https://platformio.org/][PlatformIO]], which offers better tools than the Arduino IDE.
+
+1. Upload the configuration file to the board:
+
+#+begin_src shell
+pio run -t uploadfs
+#+end_src
+
+2. Compile the project
+
+#+begin_src shell
+pio run -t compile
+#+end_src
+
+3. Upload firmware
+
+#+begin_src shell
+pio run -t upload
+#+end_src

data/example.json

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+{
+  "ssid": "",
+  "psk": "",
+  "mqtt_host": "",
+  "mqtt_user": "",
+  "mqtt_password": "",
+  "mqtt_port": 1883,
+  "mqtt_topic": "",
+  "device_id": "",
+  "sleep_time": 30,
+  "connection_attempts": 60
+}

include/config.h

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+#ifndef CONFIG_H_
+#define CONFIG_H_
+
+#include "FS.h"
+#include "LittleFS.h"
+#include <ArduinoJson.h>
+
+typedef struct {
+  const char *ssid;
+  const char *psk;
+  const char *mqtt_host;
+  const char *mqtt_user;
+  const char *mqtt_password;
+  const char *topic;
+  const char *device_id;
+  int mqtt_port;
+  long sleep_time;
+  int connection_attempts;
+} Config;
+
+void initialize_config(Config *config, StaticJsonDocument<512> json);
+
+bool load_config_file(const char *file_path, Config *config);
+
+long minutes_to_microseconds(int minutes);
+
+#endif // CONFIG_H_

include/wlan.h

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+#ifndef WLAN_H
+#define WLAN_H
+
+#include "config.h"
+#include <ESP8266WiFi.h>
+#include <PubSubClient.h>
+
+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);
+
+#endif /* WLAN_H */

platformio.ini

@@ -11,4 +11,10 @@
 [env:d1_mini]
 platform = espressif8266
 board = d1_mini
+board_build.filesystem = littlefs
 framework = arduino
+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

shell.nix

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 with pkgs;
 
-mkShell { buildInputs = [ platformio ]; }
+mkShell { buildInputs = [ platformio clang ]; }

src/config.cpp

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+#include "config.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"];
+}
+
+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;
+}
+
+long minutes_to_microseconds(int minutes) { return (minutes * 6e7); }

src/main.cpp

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+#include "config.h"
+#include "wlan.h"
+#include <Arduino.h>
+#include <DHT.h>
+
+#define DHTTYPE DHT22
+#define DHTPIN 4
+DHT dht(DHTPIN, DHTTYPE);
+
+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);
+}
+
+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);
+}
+
+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);
+}

src/wlan.cpp

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+#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 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_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 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) {
+  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;
+}
+
+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);
+}