Modified Arduino MKRWAN 1300 LoraSendAndReceive.ino example for use with Helium Network

LoraSendAndReceive-Helium.ino

/*
  Lora Send And Receive
  This sketch demonstrates how to send and receive data with the MKR WAN 1300/1310 LoRa module.
  This example code is in the public domain.
*/

#include <MKRWAN.h>

#include <CayenneLPP.h>
DynamicJsonDocument jsonBuffer(4096);
CayenneLPP lpp(51);
JsonArray root = jsonBuffer.to<JsonArray>();


// My device has the Murata chip so I used this instead of "LoRaModem modem();"
LoRaModem modem(Serial1);

#include "arduino_secrets.h"
// Please enter your sensitive data in the Secret tab or arduino_secrets.h
String appEui = SECRET_APP_EUI;
String appKey = SECRET_APP_KEY;

void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  while (!Serial);
  // change this to your regional band (eg. US915, AS923, ...)
  if (!modem.begin(US915)) {
    Serial.println("Failed to start module");
    while (1) {}
  };
  Serial.print("Your module version is: ");
  Serial.println(modem.version());
  Serial.print("Your device EUI is: ");
  Serial.println(modem.deviceEUI());

  // I copied this code for enabling/disabling the channels from hpssjellis on Github (thanks!)
  Serial.println("Now Disabling all channels and enable channel 1 only for Helium ");

  modem.disableChannel(0);
  modem.enableChannel(1);    // only one enabled for Helium
  modem.disableChannel(2);
  modem.disableChannel(3);
  modem.disableChannel(4);
  modem.disableChannel(5);
  modem.disableChannel(6);
  delay(3000);
  Serial.println("Now Joining the Helium Network ");
  // Device configured as Class C
  modem.configureClass(CLASS_C);

  int connected = modem.joinOTAA(appEui, appKey);
  if (!connected) {
    Serial.println("Something went wrong; are you indoor? Move near a window and retry");
    while (1) {}
  }

  // Set poll interval to 60 secs.
  modem.minPollInterval(60);
  // NOTE: independently by this setting the modem will
  // not allow to send more than one message every 2 minutes,
  // this is enforced by firmware and can not be changed.
}

void loop() {
  Serial.println();
  Serial.println("Enter a message to send to network");
  Serial.println("(make sure that end-of-line 'NL' is enabled)");

  while (!Serial.available());
  String msg = Serial.readStringUntil('\n');

  Serial.println();
  Serial.print("Sending: " + msg + " - ");
  for (unsigned int i = 0; i < msg.length(); i++) {
    Serial.print(msg[i] >> 4, HEX);
    Serial.print(msg[i] & 0xF, HEX);
    Serial.print(" ");
  }
  Serial.println();

// Code for adding payload to Cayenne LPP packet. Using temperature as an example. Input a numerical value for the message in the serial monitor.
  lpp.reset();
  lpp.addTemperature(1, msg.toInt());
  lpp.decode(lpp.getBuffer(), lpp.getSize(), root);
  serializeJsonPretty(root, Serial);
  Serial.println();
  
  int err;
  modem.beginPacket();
  // Using modem.write instead of modem.print in the original LoraSendAndReceive example becuase we are passing a buffer of bytes.
  modem.write(lpp.getBuffer(), lpp.getSize());
  err = modem.endPacket(true);
  if (err > 0) {
    Serial.println("Message sent correctly!");
  } else {
    Serial.println("Error sending message :(");
    Serial.println("(you may send a limited amount of messages per minute, depending on the signal strength");
    Serial.println("it may vary from 1 message every couple of seconds to 1 message every minute)");
  }
  delay(1000);
  if (!modem.available()) {
    Serial.println("No downlink message received at this time.");
    return;
  }
  char rcv[64];
  int i = 0;
  while (modem.available()) {
    rcv[i++] = (char)modem.read();
  }
  Serial.print("Received: ");
  for (unsigned int j = 0; j < i; j++) {
    Serial.print(rcv[j] >> 4, HEX);
    Serial.print(rcv[j] & 0xF, HEX);
    Serial.print(" ");
  }
  Serial.println();
}