ss.println("AT+SENDB=0,2,4,11223344");//confirm status,Fport,payload length,payload(HEX)

    uint8_t payload[2];
    int var = 12450;

    payload[0] = var >> 8;
    payload[1] = var;

    ss.print("AT+SENDB=0,2,");
    ss.print(sizeof(payload));
    ss.print(",");
    for (int i = 0; i < sizeof(payload); i++) {
      ss.print(payload[i], HEX);
    }
    ss.println("");

function Decoder(bytes, port) {
  var decoded_var = bytes[0] << 8 | bytes[1];

    return {
      var: decoded_var
    }
}

#include <SoftwareSerial.h>

String inputString = "";         // a String to hold incoming data
bool stringComplete = false;     // whether the string is complete

long old_time = millis();
long new_time;

long uplink_interval = 30000;

bool time_to_at_recvb = false;
bool get_LA66_data_status = false;

bool network_joined_status = false;

SoftwareSerial ss(10, 11); // Arduino RX, TX ,

char rxbuff[128];
uint8_t rxbuff_index = 0;

void setup() {
  // initialize serial
  Serial.begin(9600);

  ss.begin(9600);
  ss.listen();

  // reserve 200 bytes for the inputString:
  inputString.reserve(200);

  ss.println("ATZ");//reset LA66
}

void loop() {

  new_time = millis();

  if ((new_time - old_time >= uplink_interval) && (network_joined_status == 1)) {
    old_time = new_time;
    get_LA66_data_status = false;

    //ss.println("AT+SENDB=0,2,4,11223344");//confirm status,Fport,payload length,payload(HEX)

    uint8_t payload[2];
    int var = 12450;

    payload[0] = var >> 8;
    payload[1] = var;

    ss.print("AT+SENDB=0,2,");
    ss.print(sizeof(payload));
    ss.print(",");
    for (int i = 0; i < sizeof(payload); i++) {
      ss.print(payload[i], HEX);
    }
    ss.println("");

  }

  if (time_to_at_recvb == true) {
    time_to_at_recvb = false;
    get_LA66_data_status = true;
    delay(1000);

    ss.println("AT+CFG");
  }

  while ( ss.available()) {
    // get the new byte:
    char inChar = (char) ss.read();
    // add it to the inputString:
    inputString += inChar;

    rxbuff[rxbuff_index++] = inChar;

    if (rxbuff_index > 128)
      break;

    // if the incoming character is a newline, set a flag so the main loop can
    // do something about it:
    if (inChar == '\n' || inChar == '\r') {
      stringComplete = true;
      rxbuff[rxbuff_index] = '\0';

      if (strncmp(rxbuff, "JOINED", 6) == 0) {
        network_joined_status = 1;
      }

      if (strncmp(rxbuff, "Dragino LA66 Device", 19) == 0) {
        network_joined_status = 0;
      }

      if (strncmp(rxbuff, "Run AT+RECVB=? to see detail", 28) == 0) {
        time_to_at_recvb = true;
        stringComplete = false;
        inputString = "\0";
      }

      if (strncmp(rxbuff, "AT+RECVB=", 9) == 0) {
        stringComplete = false;
        inputString = "\0";
        Serial.print("\r\nGet downlink data(FPort & Payload) ");
        Serial.println(&rxbuff[9]);
      }

      rxbuff_index = 0;

      if (get_LA66_data_status == true) {
        stringComplete = false;
        inputString = "\0";
      }
    }
  }

  while ( Serial.available()) {
    // get the new byte:
    char inChar = (char) Serial.read();
    // add it to the inputString:
    inputString += inChar;
    // if the incoming character is a newline, set a flag so the main loop can
    // do something about it:
    if (inChar == '\n' || inChar == '\r') {
      ss.print(inputString);
      inputString = "\0";
    }
  }

  // print the string when a newline arrives:
  if (stringComplete) {
    Serial.print(inputString);

    // clear the string:
    inputString = "\0";
    stringComplete = false;
  }
}