Problem joining helium LoRaWAN network

[ricardoneves93]

Hello everyone. First of all I wanna thank to all contributors of this library it is great to see LoRaWAN capabilities in action while this lib makes things easier.

I am making a POC to send data over helium network and I am using 2 different boards heltec_wifi_lora_32_V2 and ttgo-lora32-v21. I am able to join (sometimes) to the network, send uplink and receive downlink messages which is fascinating considering the distance that sometime I am from the hotspot that I am connected.

However I am having issues when joining a network. Sometimes it works, sometimes a couple of join requests fail and after some attempts it succeeds. But sometimes I wait hours and even with lots of hotspots in less than 1km range it seems that I am not to join. This happens on both boards and it does not seem to be an hardware issue.

What is more weird is that when I look into helium console I see Join Request followed by a Join accept for all join tries, but my device doesn't seem to receive the Join Accept message which from what I understand is a downlink message.

Since Helium network only supports Class A devices and the downlink window (Join accept) is after the uplink request (Join Request) it seems to be a time synchronization sensitive transaction and I believe that might be a cause of the problem.

The code that I have is based in some examples found online.

But basically the connect code is this one

  // LMIC init
  os_init();

  // Reset the MAC state. Session and pending data transfers will be discarded.
  LMIC_reset();
  LMIC_setClockError(MAX_CLOCK_ERROR * 1 / 100);

  // Setting to false
  LMIC_setAdrMode(0);

  LMIC.rx1DrOffset = DR_SF7B;
  LMIC.dn2Dr = DR_SF7B;
  LMIC_setDrTxpow(DR_SF7B, 14);

  LMIC_startJoining();

I am using this pins config for ttgo-lora32-v21

#define LORA_NSS 18
#define LORA_RST 23
#define LORA_DIO0 26
#define LORA_DIO1 33
#define LORA_DIO2 32

const lmic_pinmap lmic_pins = {
  .nss = LORA_NSS,
  .rxtx = LMIC_UNUSED_PIN,
  .rst = LORA_RST,
  .dio = {LORA_DIO0, LORA_DIO1, LORA_DIO2},
  .rxtx_rx_active = 0,
  .rssi_cal = 10,
  .spi_freq = 8000000
};

And I have created the void onEvent(ev_t ev) function that receives the event EV_JOINING followed by EV_JOIN_TXCOMPLETE.

If someone can give me a clue of what is going on it would be awesome.
Thanks again,
Ricardo Neves

[terrillmoore]

What region are you using? Can you post your LMIC config file? Thanks!

[ricardoneves93]

Hey @terrillmoore I forgot to mention i am on eu868 region. Are you speaking about this file? project_config/lmic_project_config.h

[ricardoneves93]

In the file project_config/lmic_project_config.h

#define CFG_eu868 1
#define CFG_sx1276_radio 1

However i forgot to mention that I am using build flags for this which I believe will override the config file, right? Let me show my config:

[env:ttgo-lora32-v21]
platform = espressif32
board = ttgo-lora32-v21
framework = arduino
lib_deps = 
	mcci-catena/MCCI LoRaWAN LMIC library@^4
	sabas1080/CayenneLPP@^1.1.0
build_flags = 
	-D hal_init=LMICHAL_init
	-D CFG_eu868=1
	-D CFG_sx1276_radio=1
	-D ARDUINO_LMIC_PROJECT_CONFIG_H_SUPPRESS
	-D DISABLE_PING
	-D DISABLE_BEACONS
	-D USE_ORIGINAL_AES
	-D BOARD_CFG=\"boards/ttgo_lora32_v21.h\"

[terrillmoore]

Yes, that's the file. But you already gave me the answer: EU868.

Gateways are bandwidth limited by regulations in EU868. You very quickly run out of bandwidth if doing Join testing; and typically the gateway just drops the join accept message in that case. (Unless you have lots of coverage -- several gateways in range of the device, in which case, the network might be able to use other gateways.)

It's likely that what you're seeing is expected. To be sure, we'd need to hook up a board to a network simulator (that doesn't have that limitation) and see if we get good downlink reception. I have a Heltec board, and the network simulator, but time... is a problem. My colleagues at MCCI also have access to a simulator, but they don't have ESP32 boards with LoRa.

However, please post your test app (as a zip file) and perhaps we can arrange something. I've been meaning to add an ESP32 to my test matrix, because they're so widely used.

[terrillmoore]

OK. In that case, it's likely that the ESP32 board has error, or your sketch is doing something that makes the LMIC unhappy. Can you post your sketch?

[ricardoneves93]

Yes, do you want a zip file?

[ricardoneves93]

lorawandevice.zip
I've omitted the DEVEUI and APPKEY on board configuration files.
If you somehow need them I can send them privately.

[terrillmoore]

I don't see anything wrong with the sketch, so either there's an RF problem, or there's a problem with clock accuracy.

If you add -D LMIC_ENABLE_arbitrary_clock_error=1 to your configuration settings, you can then set the clock error to 5% (You're already setting to 1%). That might help. If it does, we know where to look, approximately.

If not, it may be necessary to hook up the network simulator.

[ricardoneves93]

So I retested with -D LMIC_ENABLE_arbitrary_clock_error=5 build flag and it seems that it fails as well to connect to network. I have the exact same behavior as before. Sometimes it connects in the first try, then it takes 2 or 3 tries. And there are times that it never connects with 30 retries...

Is there any other solution for this? Or is the simulator the best tool?