Initial Commit

.gitignore

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+.pio
+.vscode/.browse.c_cpp.db*
+.vscode/c_cpp_properties.json
+.vscode/launch.json
+.vscode/ipch

.vscode/extensions.json

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+{
+    // See http://go.microsoft.com/fwlink/?LinkId=827846
+    // for the documentation about the extensions.json format
+    "recommendations": [
+        "platformio.platformio-ide"
+    ],
+    "unwantedRecommendations": [
+        "ms-vscode.cpptools-extension-pack"
+    ]
+}

include/README

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+
+This directory is intended for project header files.
+
+A header file is a file containing C declarations and macro definitions
+to be shared between several project source files. You request the use of a
+header file in your project source file (C, C++, etc) located in `src` folder
+by including it, with the C preprocessing directive `#include'.
+
+```src/main.c
+
+#include "header.h"
+
+int main (void)
+{
+ ...
+}
+```
+
+Including a header file produces the same results as copying the header file
+into each source file that needs it. Such copying would be time-consuming
+and error-prone. With a header file, the related declarations appear
+in only one place. If they need to be changed, they can be changed in one
+place, and programs that include the header file will automatically use the
+new version when next recompiled. The header file eliminates the labor of
+finding and changing all the copies as well as the risk that a failure to
+find one copy will result in inconsistencies within a program.
+
+In C, the convention is to give header files names that end with `.h'.
+
+Read more about using header files in official GCC documentation:
+
+* Include Syntax
+* Include Operation
+* Once-Only Headers
+* Computed Includes
+
+https://gcc.gnu.org/onlinedocs/cpp/Header-Files.html

lib/README

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+
+This directory is intended for project specific (private) libraries.
+PlatformIO will compile them to static libraries and link into the executable file.
+
+The source code of each library should be placed in a separate directory
+("lib/your_library_name/[Code]").
+
+For example, see the structure of the following example libraries `Foo` and `Bar`:
+
+|--lib
+|  |
+|  |--Bar
+|  |  |--docs
+|  |  |--examples
+|  |  |--src
+|  |     |- Bar.c
+|  |     |- Bar.h
+|  |  |- library.json (optional. for custom build options, etc) https://docs.platformio.org/page/librarymanager/config.html
+|  |
+|  |--Foo
+|  |  |- Foo.c
+|  |  |- Foo.h
+|  |
+|  |- README --> THIS FILE
+|
+|- platformio.ini
+|--src
+   |- main.c
+
+Example contents of `src/main.c` using Foo and Bar:
+```
+#include <Foo.h>
+#include <Bar.h>
+
+int main (void)
+{
+  ...
+}
+
+```
+
+The PlatformIO Library Dependency Finder will find automatically dependent
+libraries by scanning project source files.
+
+More information about PlatformIO Library Dependency Finder
+- https://docs.platformio.org/page/librarymanager/ldf.html

platformio.ini

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+; PlatformIO Project Configuration File
+;
+;   Build options: build flags, source filter
+;   Upload options: custom upload port, speed and extra flags
+;   Library options: dependencies, extra library storages
+;   Advanced options: extra scripting
+;
+; Please visit documentation for the other options and examples
+; https://docs.platformio.org/page/projectconf.html
+
+[env:d1_mini]
+platform = espressif8266
+board = d1_mini
+framework = arduino
+lib_deps = knolleary/PubSubClient@^2.8

src/main.cpp

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+#include <Arduino.h>
+#include <ESP8266WiFi.h>
+#include <PubSubClient.h>
+               
+const char* WIFI_SSID = "Mi 10";
+const char* WIFI_PASS = "12345678";
+
+unsigned long lastMqttAttemptMs = 0;
+const unsigned long MQTT_RETRY_MS = 3000;
+
+const char* MQTT_HOST = "broker.hivemq.com";
+const uint16_t MQTT_PORT = 1883;
+const char* MQTT_CLIENTID = "bbsgut-dht22-d1mini-02";
+const char* TOPIC_TEMP = "bbsgut/sensor/dht22/temperature";
+const char* TOPIC_HUM = "bbsgut/sensor/dht22/humidity";
+const char* TOPIC_STATUS = "bbsgut/receiver/status";
+
+WiFiClient espClient;
+PubSubClient mqtt(espClient);
+
+String messageBuffer{};
+String temperature{};
+String humidity{};
+
+void writeToUart() {
+  if(!temperature.isEmpty() && !humidity.isEmpty()) {
+    Serial.print("{\"temp\":");
+    Serial.print(temperature);
+    Serial.print(",\"hum\":");
+    Serial.print(humidity);
+    Serial.print("}\n");
+  }
+}
+
+void callback(char* topic, byte* message, unsigned int length) {
+  messageBuffer = "";
+  
+  for (unsigned int i = 0; i < length; i++) {
+    messageBuffer += (char)message[i];
+  }
+
+  if(!messageBuffer.isEmpty()) {
+    if (String(topic) == TOPIC_TEMP) {
+      temperature = messageBuffer;
+    }
+    if (String(topic) == TOPIC_HUM) {
+      humidity = messageBuffer;
+    }
+  }
+
+  writeToUart();
+}
+
+bool ensureWifi() {
+    if (WiFi.status() == WL_CONNECTED) return true;
+    WiFi.mode(WIFI_STA);
+    WiFi.begin(WIFI_SSID, WIFI_PASS);
+    unsigned long t0 = millis();
+    while (WiFi.status() != WL_CONNECTED && millis() - t0 < 15000) {
+        delay(120);
+    }
+    return WiFi.status() == WL_CONNECTED;
+}
+
+bool ensureMqtt() {
+    if (mqtt.connected()) return true;
+    if (!ensureWifi()) return false;
+
+    if (millis() - lastMqttAttemptMs < MQTT_RETRY_MS) return false;
+    lastMqttAttemptMs = millis();
+
+    if (mqtt.connect(MQTT_CLIENTID, nullptr, nullptr, TOPIC_STATUS, 0, true, "offline")) {
+        return true;
+    }
+    return false;
+}
+
+void setup() {
+  delay(100);
+
+  WiFi.mode(WIFI_STA);
+  WiFi.begin(WIFI_SSID, WIFI_PASS);
+
+  mqtt.setServer(MQTT_HOST, MQTT_PORT);
+  mqtt.setCallback(callback);
+
+  Serial.begin(9600);
+  ensureMqtt();
+  delay(300);
+  mqtt.subscribe(TOPIC_TEMP);
+  mqtt.subscribe(TOPIC_HUM);
+}
+
+void loop() {
+  if (!mqtt.connected()) {
+    if (ensureMqtt()) {
+      mqtt.subscribe(TOPIC_TEMP);
+      mqtt.subscribe(TOPIC_HUM);
+    }
+  }
+
+  mqtt.loop();
+
+  if(!temperature.isEmpty() && !humidity.isEmpty()) {
+    static unsigned long last = 0;
+    if (millis() - last > 1000) {
+      last = millis();
+      writeToUart();
+    }
+  }
+}

test/README

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+
+This directory is intended for PlatformIO Test Runner and project tests.
+
+Unit Testing is a software testing method by which individual units of
+source code, sets of one or more MCU program modules together with associated
+control data, usage procedures, and operating procedures, are tested to
+determine whether they are fit for use. Unit testing finds problems early
+in the development cycle.
+
+More information about PlatformIO Unit Testing:
+- https://docs.platformio.org/en/latest/advanced/unit-testing/index.html