I’ve got the DFPlayer with the GD3200B instead of the better YX5200, but it works.

As part of my game, so MQTT controlled.

Code

I’m using Soft Serial

// based on code from: 
// https://github.com/Makuna/DFMiniMp3/blob/master/examples/PlayMp3/PlayMp3.ino
// above example has no wifi/mqtt and is missing the SoftSerial include line
#include <ESP8266WiFi.h>
#include <PubSubClient.h>
#include <WiFiClient.h>
#include <DFMiniMp3.h>
#include "SoftwareSerial.h"
#include <Ethernet.h>

#define wifi_ssid "SSID"
#define wifi_password "SSIDPASS"
#define mqtt_server "MQTTSERVER"
#define mqtt_port 1883

WiFiClient espClient;
EthernetClient ethClient;
PubSubClient mqtt(espClient);

class Mp3Notify; 

SoftwareSerial secondarySerial(D6, D5); // RX, TX
typedef DFMiniMp3<SoftwareSerial, Mp3Notify> DfMp3;
DfMp3 dfmp3(secondarySerial);

class Mp3Notify
{
public:
  static void PrintlnSourceAction(DfMp3_PlaySources source, const char* action)
  {
    if (source & DfMp3_PlaySources_Sd) 
    {
        Serial.print("SD Card, ");
    }
    if (source & DfMp3_PlaySources_Usb) 
    {
        Serial.print("USB Disk, ");
    }
    if (source & DfMp3_PlaySources_Flash) 
    {
        Serial.print("Flash, ");
    }
    Serial.println(action);
  }
  static void OnError([[maybe_unused]] DfMp3& mp3, uint16_t errorCode)
  {
    // see DfMp3_Error for code meaning
    Serial.println();
    Serial.print("Com Error ");
    Serial.println(errorCode);
  }
  static void OnPlayFinished([[maybe_unused]] DfMp3& mp3, [[maybe_unused]] DfMp3_PlaySources source, uint16_t track)
  {
    Serial.print("Play finished for #");
    Serial.println(track);  

    // start next track
    track += 1;
    // this example will just start back over with 1 after track 3
    if (track > 3) 
    {
      track = 1;
    }
    dfmp3.playMp3FolderTrack(track);  // sd:/mp3/0001.mp3, sd:/mp3/0002.mp3, sd:/mp3/0003.mp3
  }
  static void OnPlaySourceOnline([[maybe_unused]] DfMp3& mp3, DfMp3_PlaySources source)
  {
    PrintlnSourceAction(source, "online");
  }
  static void OnPlaySourceInserted([[maybe_unused]] DfMp3& mp3, DfMp3_PlaySources source)
  {
    PrintlnSourceAction(source, "inserted");
  }
  static void OnPlaySourceRemoved([[maybe_unused]] DfMp3& mp3, DfMp3_PlaySources source)
  {
    PrintlnSourceAction(source, "removed");
  }
};

void setup_wifi() {
  delay(10);
  WiFi.mode(WIFI_STA);
  WiFi.begin(wifi_ssid, wifi_password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
  }
}

void setup() 
{
  setup_wifi();
  mqtt.setServer(mqtt_server, mqtt_port);
  mqtt.setCallback(callback);
  Serial.begin(115200);
  Serial.println("initializing...");

  WiFiClient espClient;
  PubSubClient mqtt(espClient);

  mqtt.setClient(espClient);
  mqtt.setServer(mqtt_server, 1883);
    
  mqtt.setCallback(callback);
  mqtt.subscribe("escape/soundin");
  
  dfmp3.begin();

  uint16_t volume = dfmp3.getVolume();
  Serial.print("volume ");
  Serial.println(volume);
  dfmp3.setVolume(24);
  
  uint16_t count = dfmp3.getTotalTrackCount(DfMp3_PlaySource_Sd);
  Serial.print("files ");
  Serial.println(count);
  
  Serial.println("starting...");

  // start the first track playing
  // dfmp3.playMp3FolderTrack(1);  // sd:/mp3/0001.mp3
}

void reconnect() {
  // Loop until we're reconnected
  while (!mqtt.connected()) {
    // Create a random client ID
    String clientId = "ESP8266Client-";
    clientId += String(random(0xffff), HEX);
    // Attempt to connect
    if (mqtt.connect(clientId.c_str())) {
      // Once connected, publish an announcement...
      mqtt.publish("escape", "sound connected");
      // ... and resubscribe
      mqtt.subscribe("escape/soundin");
    } else {
      // Wait 5 seconds before retrying
      delay(5000);
    }
  }
}


void callback(char* topic, byte* payload, unsigned int length) {
    //  digitalWrite(led, HIGH);

    String topicStr = topic;
      byte value = atoi((char*)payload);
dfmp3.playMp3FolderTrack(value);  // sd:/mp3/0001.mp3
  Serial.println(value);
}

void waitMilliseconds(uint16_t msWait)
{
  uint32_t start = millis();

  while ((millis() - start) < msWait)
  {
    dfmp3.loop(); 
    delay(1);
  }
}

void loop() 
{
  
  if (!mqtt.connected()) {
    reconnect();
  }
    mqtt.loop();
  waitMilliseconds(100);
}