#include "heltec.h"
#define BAND    915E6  //you can set band here directly,e.g. 868E6,915E6

String packet ="";
String packSize = "--";

void setup() {
  Heltec.begin(true /*DisplayEnable Enable*/, true /*Heltec.LoRa Disable*/, true /*Serial Enable*/, true /*PABOOST Enable*/, BAND /*long BAND*/);
}

void loop() {
  //receive
  int packetSize = LoRa.parsePacket();
    if (packetSize) {
      while (LoRa.available()) {
        if (packetSize) { cbk(packetSize);  }
}
  Serial.print("Recevied ");
  Serial.print(packet);
  Serial.print(" with RSSI ");
  Serial.println(LoRa.packetRssi());
  sendack();
}}

void sendack(){
  Serial.print("Sending packet ");
  Serial.println(packet);
  LoRa.beginPacket();
  LoRa.setTxPower(14,RF_PACONFIG_PASELECT_PABOOST);
  LoRa.print(packet);
  LoRa.endPacket();
}

void cbk(int packetSize) {
  packet ="";
  packSize = String(packetSize,DEC);
  for (int i = 0; i < packetSize; i++) { packet += (char) LoRa.read(); }
}