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Topic: Error Sending Packets Over 10 Bytes (Read 3493 times) previous topic - next topic



I'm trying to send data from the MKR WAN 1300 to Thing Park.  I can successfully connect via OTAA to the network. 

As long as the data stays below 10 bytes everything works fine, but as soon as I try to transmit something larger the network receives empty packets.

With a lot of experimentation I was able to figure out a pattern and this is what I have to do to make it work:

[up] Join request sent
[down] Join accepted

[up] Send <10 byte packet
[down] Receive a MAC request

[up] Send a <10 byte packet (and automatically respond to the MAC)
[down] Receive confirmation

[up] Send a >10 byte packet.  There will be 4 errors where empty packets are sent (a modem.endPacket(true) size <0) then the network will send a MAC request.  Even though the data is never transmitted this seems to satisfy the MKR that it was received.
[down] Receive the above mentioned MAC request.

[up] Send a >10 byte packet (and automatically respond to the MAC)
[down] Receive confirmation

Only after all that is done can I send packets over 10 bytes reliably.  I don't believe this is a problem with the network because other off the shelf products I've connected, such as a GPS and a temperature sensor, have no problem sending large amounts of data immediately after joining. 

This can't be the proper way to handle this, does anyone have some suggestions?  I saw this post which looks like a very similar problem, but it was apparently solved by not asking for responses.  I tried that and it did not solve my issue.  I'm using firmware version ARD-078 1.1.9.

I have this issue with all sketches, even the example ones, and used the LoraSendAndReceive example to figure out the above pattern:

Code: [Select]
  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.

#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:
  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.print("Your device EUI is: ");

  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.
  // 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("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.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(" ");

  int err;
  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)");
  if (!modem.available()) {
    Serial.println("No downlink message received at this time.");
  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(" ");

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