Android controlled bluetooth radio

#include <BluetoothSerial.h>
#include <Arduino.h>
#include <Wire.h>
#include <RDA5807M.h>


#define FIX_BAND RADIO_BAND_FM   
#define BT_DISCOVER_TIME  10000

BluetoothSerial SerialBT;
RDA5807M radio;

int stations[12] = {9110,9370,9580,9670,9740,9890,9890,10110,10280,10480,10540,10760};
int action = -1;
static bool btScanAsync = true;
static bool btScanSync = true;
int Volume = 8;
//int convert1 = 0;
float convert = 0;
void setup() {
//String myString = "";  
  Serial.begin(115200);
  SerialBT.begin("ESP32FMRadio"); //Bluetooth device name
  Serial.println("The device started, now you can pair it with bluetooth!");


  if (btScanAsync) {
    Serial.print("Starting discoverAsync...");
    if (SerialBT.discoverAsync(btAdvertisedDeviceFound)) {
      Serial.println("Findings will be reported in \"btAdvertisedDeviceFound\"");
      delay(10000);
      Serial.print("Stopping discoverAsync... ");
      SerialBT.discoverAsyncStop();
      Serial.println("stopped");
    } else {
      Serial.println("Error on discoverAsync f.e. not workin after a \"connect\"");
    }
  }
  
  if (btScanSync) {
    Serial.println("Starting discover...");
    BTScanResults *pResults = SerialBT.discover(BT_DISCOVER_TIME);
    if (pResults)
      pResults->dump(&Serial);
    else
      Serial.println("Error on BT Scan, no result!");
  }


  radio.init();
  radio.setBandFrequency(FIX_BAND, 9110);
  radio.setVolume(Volume);
  radio.setMono(false);
  radio.setMute(false);
}

void loop() {
  action = SerialBT.read();
  if (action > 0) {
    if (action < 11) {
      convert = stations[action];
      convert = convert / 100;

      String myString = String (convert,1);
      if (myString.length() == 4) {
        myString = (myString + " ");
      }
  
      Serial.println(myString );
      SerialBT.print(myString);
      radio.setBandFrequency(FIX_BAND, stations[action]);
 }
else {
  switch (action){
  case 11:
    if (Volume >0) {
    Volume --;
  radio.setVolume(Volume);
  }
  break;

  case 12:
    if (Volume < 15) {
    Volume ++;
    radio.setVolume(Volume);
      }
   break;
   
  case 13:
  radio.seekDown();
  break;

  case 14:
  radio.seekUp();
  break;

  case 15:
  convert = radio.getFrequency();
  convert = convert / 100;
  String myString = String (convert,1);
      if (myString.length() == 4) {
        myString = (myString + " ");
      }
  Serial.println(myString);
  SerialBT.print(myString);
  break;
  }
}

  }
}


void btAdvertisedDeviceFound(BTAdvertisedDevice* pDevice) {
  Serial.printf("Found a device asynchronously: %s\n", pDevice->toString().c_str());
}