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In order to send a long payload I've created the following function:

void splitMSG(const char *msg, const int arraySize, const int len)
{
  Serial.print("Array size: ");
  Serial.println(arraySize);
  byte numPackets = (int)(arraySize / len);
  byte P_iterator = 0;
  if (arraySize % len > 0)
  {
    numPackets++;
  }
  Serial.print("num_Packets: ");
  Serial.println(numPackets);

  while (P_iterator < numPackets)
  {
    char t[len + 1];
    char *ptr1 = msg + P_iterator * (len);
    strncpy(t, ptr1, len);
    t[len + 1] = '\0';
    Serial.println(t);
    radio.write(&t, sizeof(t));
    P_iterator++;
  }
}

The split message is sent to the serial monitor to verify it is as expected.

**On the sending device :

void loop()
{
  radio.stopListening();

  char send_msg[] = "1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ";  // <----- input msg
  splitMSG(send_msg, sizeof(send_msg), 10);                  // <----- split to 10 bytes a packet
  delay(1000);
  // Serial.println("±±±±±±±±");
}

On the serial monitor I get:

08:06:17.569 -> Array size: 37
08:06:17.569 -> num_Packets: 4
08:06:17.569 -> 1234567890
08:06:17.569 -> ABCDEFGHIJ
08:06:17.569 -> KLMNOPQRST
08:06:17.569 -> UVWXYZ

**On the receiving device:

void loop()
{
  if (radio.available())
  {
    while (radio.available())
    {
      char buf[32];
      radio.read(&buf, sizeof(buf));
      Serial.print("got msg: ");
      Serial.println(buf);
      radio.flush_rx();
    }
  }

  delay(100);
}

On the serial monitor I get:

08:08:18.462 -> got msg: 1234567890⸮⸮⸮⸮
08:08:18.561 -> got msg: ABCDEFGHIJKLMNOPQRSTUVWXYZ
08:08:19.555 -> got msg: 1234567890ABCDEFGHIJKLMNOPQRST⸮⸮⸮⸮
08:08:20.549 -> got msg: 1234567890ABCDEFGHIJKLMNOPQRST⸮⸮⸮⸮
08:08:21.576 -> got msg: 1234567890ABCDEFGHIJKLMNOPQRST⸮⸮⸮⸮
08:08:22.570 -> got msg: 1234567890ABCDEFGHIJKLMNOPQRST⸮⸮⸮⸮
08:08:22.669 -> got msg: UVWXYZ

Does the problem with radio.write ' buffer , or the way I split the message ?

1 Answer 1

2
t[len + 1] = '\0';

Your array is declared as having len+1 bytes of storage. So the last index is len, not len+1. You're writing the zero one past the end of the array, thus you're not transmitting it (and sending one byte of "garbage" instead).

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