Added already started arduino project

src/mqtt_esp32/mqtt_esp.ino

+#include <WiFi.h>
+#include <PubSubClient.h>
+#include <HardwareSerial.h>
+
+#define MATRIX_SIZE 10   // 10x10
+#define IMG_DATA_SIZE MATRIX_SIZE * MATRIX_SIZE * 3 //DATA SIZE FOR ONE MATRIX = RGB * MATRIX_SIZE
+
+// WiFi
+const char *ssid = "uni-ete2"; // Enter your WiFi name
+const char *password = "uni-ete2-esp32";  // Enter WiFi password
+
+// MQTT Broker
+const char *mqtt_broker = "192.168.1.103";
+const char *topic_send = "fromesp";
+const char *topic_rcv = "toesp";
+const int mqtt_port = 1883;
+
+WiFiClient espClient;
+PubSubClient client(espClient);
+
+// UART2
+HardwareSerial SerialPort(2); // use UART2
+
+uint8_t cluster_size_x = 1;
+uint8_t cluster_size_y = 1;
+
+void setup() 
+{
+   // Set software serial baud to 115200;
+    Serial.begin(115200);
+
+    // Set UART2 serial
+    SerialPort.begin(115200, SERIAL_8N1, 16, 17); 
+
+    // Connecting to a WiFi network
+    WiFi.begin(ssid, password);
+    while (WiFi.status() != WL_CONNECTED) {
+        delay(500);
+        Serial.println("Connecting to WiFi..");
+    }
+    Serial.println("Connected to the Wi-Fi network");
+
+    //connecting to a mqtt broker
+    client.setServer(mqtt_broker, mqtt_port);
+    client.setCallback(callback);
+    client.setBufferSize(2000);
+
+    while (!client.connected()) 
+    {
+      String client_id = "esp32-client-";
+      client_id += String(WiFi.macAddress());
+      Serial.printf("The client %s connects to the public MQTT broker\n", client_id.c_str());
+      if (client.connect(client_id.c_str())) 
+      {
+          Serial.println("Public EMQX MQTT broker connected");
+      } else 
+      {
+          Serial.print("failed with state ");
+          Serial.print(client.state());
+          delay(2000);
+      }
+    }
+
+    // Publish and subscribe
+    client.publish(topic_send, "Hi, I'm ESP32 ^^");
+    client.subscribe(topic_rcv);
+}
+
+uint8_t* mqtt_packet_to_raw(uint8_t* packet, unsigned int* length)
+{
+  for(int i = 0; i < *length; i++)
+  {
+    if(packet[i] == ':')
+    {
+      *length -= i - 2 - 2;
+      return packet + i + 2;
+    }
+  }
+
+  return NULL;
+}
+
+void send_data_to_matrix(uint8_t idx, uint8_t idy, uint8_t* data, uint32_t length)
+{
+  // ADD ID TO LEN
+  length += 2;
+
+  // SEND UART PACKET HEADER
+  SerialPort.print((char)0x77);
+  SerialPort.print((char)length);
+
+  // SEND MATRIX ID
+  SerialPort.print((char)idx);
+  SerialPort.print((char)idy);
+
+  uint8_t crc = 0;
+  // SEND RGB DATA
+  for(int i = 0; i < length; i+=3)
+  {
+    // COMPUTE COLOR IN 16 BITS
+    uint8_t r = data[i] & 0x1F;
+    uint8_t g = data[i+1] & 0x3F;
+    uint8_t b = data[i+2] & 0x1F ;
+    uint16_t rgb = r << 11 | g << 5 | b;
+
+    // SPLIT ON 8 BITS
+    uint8_t rgb_0 = rgb >> 8;
+    uint8_t rgb_1 = rgb & 0x0F;
+
+    // COMPUTE CRC
+    crc = crc ^ rgb_0 ^ rgb_1;
+
+    // SEND RGB
+    SerialPort.print((char) rgb_0);
+    SerialPort.print((char) rgb_1);
+  }
+
+  // SEND UART PACKET FOOTER
+  SerialPort.print((char)(crc ^ length));
+  SerialPort.print((char)0xAA);
+}
+
+void callback(char *topic, byte *payload, unsigned int length) 
+{
+  // TERMINAL SERIAL
+  Serial.print("Message arrived in topic: ");
+  Serial.println(topic);
+
+  // GET RAW DATA
+  uint8_t* raw_data = mqtt_packet_to_raw(payload, &length);
+
+  // SEND UART PACKET FOR EACH MATRIX
+  for(int x = 0; x < cluster_size_x; x++)
+  {
+    for(int y = cluster_size_y - 1; y >= 0; y--)
+    {
+      // SEND UART PACKET
+      send_data_to_matrix(x, y, raw_data, IMG_DATA_SIZE);
+
+      // MOVE FORWARD IN DATA
+      raw_data += IMG_DATA_SIZE;
+    }
+  }
+}
+
+void loop() {
+  // put your main code here, to run repeatedly:
+  client.loop();
+}