LoPy4 issue with OTAA join confirm

  • I use LoPy4 with the latest firmware and try to join the node. In the TTN console I see the activation requests each 3 min but it never joined and lopy continues join requests. As I am probably not in best location with gateway coverage I have to modify dr to 3 or 0. With 4 and 5 it does not work. As far as I see on the SDR receiver by default it uses 5. However with < 3 it is visible in the console so the transmission is received from the gateway.

    lora.join(activation=LoRa.OTAA, auth=(dev_eui, app_eui, app_key), timeout=0, dr=3)

    I am in the EU area and these are my first steps with LoRa. What might cause this? I was thinking about these options:

    • Not sure how gateway join accept works but if I transmit the join requests with SF12 (dr=0, for example) and gateway transmit back with SF7 then I won't be able to receive it. But not sure how this works. I expect that if I use SF12 for join then it should reply with SF12 but I might be wrong and maybe this is a setting of the gateway.

    • My LoPy4 is bought 2nd hand and I am not 100% sure that it's ok. It might have receiver problems...

    Any ideas? I will try ABP where is does not need join confirmation, also will test it from closer location to proper gateway.

  • Actually it joined the TTN network from my home location. But it needs a lot of time, so I guess it's really issue with the radio layer. I couldn't do downlink though. Apparently my location (Sofia, Bulgaria) is poorly covered and I have to install my own gateway to be able to use LoRa around the area...

  • I tried from my work indoor which is close to one of the best gateways but it's not heard at all. Anyway, testing now from home but outside and 3 gateways receive the join request:

      "time": "2019-11-15T21:00:44.263527846Z",
      "frequency": 868.3,
      "modulation": "LORA",
      "data_rate": "SF12BW125",
      "coding_rate": "4/5",
      "gateways": [
          "gtw_id": "eui-7276ff00080e030a",
          "timestamp": 510769180,
          "time": "2019-11-15T21:00:44.197755Z",
          "channel": 6,
          "rssi": -116,
          "snr": -12,
          "rf_chain": 1
          "gtw_id": "eui-b827ebfffe3879a8",
          "timestamp": 921591452,
          "time": "",
          "channel": 1,
          "rssi": -118,
          "snr": -11.2,
          "rf_chain": 1
          "gtw_id": "eui-b827ebfffed2f153",
          "timestamp": 1141649028,
          "time": "2019-11-15T21:00:44.239452Z",
          "channel": 1,
          "rssi": -117,
          "snr": -16.8,
          "rf_chain": 1

    Not sure practically how good are these RSSI and SNRs but does not look very well.

  • @nkitanov You cannot make any valid assumption about the gateway. If you look at the TTN gateway map, many of these are indoor, and very few have a high gain outdoor antenna. It may as well be that your place has a lot of RF noise, making reception of small signals difficult, while the strong send signal still sticks out.
    For telling, whether you set-up works, you have to be close to the gateway or run you own gateway.

  • Thanks. It might be, but still it's bit unusual from radio layer point of view. If I can reach the gateway with my tiny antenna, why can't receive the gateway response which usually have better antenna outdoor. Of course there might be some unique propagation challenges for the response signal... Will do some more testing today. I still consider RX circuit issues on my lopy.

  • @nkitanov AFAIK, TTN replies join requests with SF12 at SF12, but will then switch to SF9 and receive window 2 for downlink messages. The OTAA join response will tell the node to act accordingly. The LoRA node software works well. Only using the LoPyx for FiPy as gateway is not recommended, not even as a single channel gateway.
    But I would assume that in your case is is just the poor receive condition, which prevents you form receiving downlink messages. ABP should work, as long as you do not expect to receive downlink messages.

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