MKRWAN1300 project HELP!

Projects Programming
1

Hi guys!

I am really stuck on this project, I'm pretty noob at all this so apologies in advance :D. I am trying to use the MKR WAN 1300 to send LDR sensor and Sharp sensor data to the TTN. So far, here is my following code which I used.

/*
  Lora Send And Receive
  This sketch demonstrates how to send and receive data with the MKR WAN 1300 LoRa module.
  This example code is in the public domain.
*/
#define LDRpin A0 // pin where we connected the LDR and the resistor

int LDRValue = 0;     // result of reading the analog pin


#include <MKRWAN.h>

LoRaModem modem;

// Uncomment if using the Murata chip as a module
// 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(AS923)) {
    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());

  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() {
  LDRValue = analogRead(LDRpin); // read the value from the LDR
  //Serial.println(LDRValue);      // print the value to the serial port
  delay(10);                    // wait a little
  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 + " - ");
 Serial.print("Sending: " + LDRValue + " - ");
  for (unsigned int i = 0; i < msg.length(); i++) {
    Serial.print(msg[i] >> 4, HEX);
    Serial.print(msg[i] & 0xF, HEX);
    Serial.print(" ");
  }
  for (unsigned int i = 0; i < LDRValue.length(); i++) {
    Serial.print(LDRValue[i] >> 4, HEX);
    Serial.print(LDRValue[i] & 0xF, HEX);
    Serial.print(" ");
  }
  Serial.println();

  int err;
  modem.beginPacket();
  modem.print(msg);
  modem.print(LDRValue);
  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();
}

I am getting an error message that :

Arduino: 1.8.5 (Windows 10), Board: "Arduino MKR WAN 1300"

C:\Users\Admin\AppData\Local\Temp\arduino_modified_sketch_912980\LoraSendAndReceive.ino: In function 'void loop()':

LoraSendAndReceive:63: error: invalid operands of types 'const char*' and 'const char [4]' to binary 'operator+'

Serial.print("Sending: " + LDRValue + " - ");

^

LoraSendAndReceive:69: error: request for member 'length' in 'LDRValue', which is of non-class type 'int'

for (unsigned int i = 0; i < LDRValue.length(); i++) {

^

LoraSendAndReceive:70: error: invalid types 'int[unsigned int]' for array subscript

Serial.print(LDRValue >> 4, HEX);

  • ^*
    LoraSendAndReceive:71: error: invalid types 'int[unsigned int]' for array subscript
    _ Serial.print(LDRValue & 0xF, HEX);_
    * ^*
    exit status 1
    invalid operands of types 'const char*' and 'const char [4]' to binary 'operator+'
    This report would have more information with
    "Show verbose output during compilation"
    option enabled in File -> Preferences.
    PLEASE HELP!
2

Serial.print("Sending: " + LDRValue + " - ");

I wonder why it does not like that line, the complier is clearly pointing to it as an error ?

Was it in the original un-modified code ?

3

It seems like you are getting confused into thinking you can work with any type as you would do with Strings.

This code:

KingVichai:

  Serial.print("Sending: " + msg + " - ");

Should be written like this:

 Serial.print("Sending: ");
  Serial.print(msg);
  Serial.print(" - ");

There is one other occurrence of this issue in your code.

In this code:

KingVichai:

  for (unsigned int i = 0; i < LDRValue.length(); i++) {

Serial.print(LDRValue[i] >> 4, HEX);
   Serial.print(LDRValue[i] & 0xF, HEX);
   Serial.print(" ");
 }

The data type of LDRValue is int:

KingVichai:

int LDRValue = 0;     // result of reading the analog pin

yet you're trying to treat it as though it were a String, thus the rest of the errors.

KingVichai:
Serial.print(LDRValue >> 4, HEX);

  • ^*
    LoraSendAndReceive:71: error: invalid types 'int[unsigned int]' for array subscript
    _ Serial.print(LDRValue & 0xF, HEX);_
    * ^*
    exit status 1
    invalid operands of types 'const char*' and 'const char [4]' to binary 'operator+'
    This report would have more information with
    "Show verbose output during compilation"
    option enabled in File -> Preferences.
    PLEASE HELP!
    [/quote]
    Notice how the code in the error message is doesn't match your sketch and all the text turned to italics? This is because the forum interpreted part of the code as markup for italics. For this reason, please use code tags when you post error or warning messages, as you did with your code (thanks!).;