RN2903 "invalid_data_len" on AU915 over 24 Bytes/11 Characters

[arjanvanb (Arjan)]

@ElectronicallyE

  // transmit a startup message
  //myLora.tx("Hello!");

  // setting the frequency plan to AU915
  myLora.setFrequencyPlan(TTN_AU);

I’d first set the frequency plan before sending anything.

Beware you also still have a reference to US, despite the comment stating otherwise:

  // Setting the frequency plan to AU915
  myLora.setFrequencyPlan(TTN_US);

@ElectronicallyE

24 bytes, or 11 characters

Even though most use cases should not use text, I’d not expect a library to support 16 bits characters or some UTF-encodig, if that’s what causes that difference. How many bytes of application payload do you see in TTN Console when sending, say, 2 bytes? Maybe the library is adding its own payload?

@ElectronicallyE

I have also tried turning the ADR on in line 290 as I am using ABP

ADR is unrelated to whether you’re using OTAA or ABP.

@ElectronicallyE

if I wanted to send a GPS coordinate, I would not have enough space

Actually, that might only need 6 bytes; see Best practices when sending GPS location data [HowTo].