RAK811 trackernode

  • Ok, let's dig a little deeper:
    SNR, RSSI, DR (SF), Frequency and so on are Metadata. This data comes in a defined protocol from the Gateway. I suppose you also see a payload (hex string). This is the data from your node. As TTN has no way to know what you encoded in this data, you have to tell TTN what to do with this data/what is encoded. If you took the standard RAK811BreakBoard GIT repository, your RAK is sending in the Cayenne LPP payload encoding.
    If every third of your payload starts with "01 88", then your RAK sends GPS data. (01 means LPP channel 2, 88 means GPS).
    There should be two other types of payload sent in the standard firmware: some that are starting with 02 67 (transmitts temperature and battery values) and some that are starting with 03 71 which are the acceleratometer-values.
    Regards, Edi

  • Well fired it up and it seems it is sending GPS.

    018808078EFFB3DE004074 is one payload..

    I honestly thought the GPS data would be in the metadata unless its embedded in the time.

    "time": "2018-05-30T09:52:13.966007482Z",
    "frequency": 867.9,
    "modulation": "LORA",
    "data_rate": "SF12BW125",
    "coding_rate": "4/5",
    "gateways": [
    "gtw_id": "eui-b827ebfffef0160d",
    "timestamp": 550209956,
    "time": "2018-05-30T09:52:13.946794Z",
    "channel": 7,
    "rssi": -41,
    "snr": 9.5

  • Well it seems to be working now.

    Last thing is I want to use the node tracker as a range finder. Therefore I want to send the GPS data like every 5 seconds.

    Is that possible?


  • @ikilby That looks great, at least if you are around Walsall/UK. If you would activate Cayenne LPP as a payload decoder, you would see some fields above the metadata-info as in this example:
    0_1527678930046_2018-05-30 13_14_43-The Things Network Console.png (well not exactly like this, you wouldn't see the analog_in_4, this is the battery value in my modified firmware).
    Of course it's possible to send your position every 5 seconds, but only if you disable accelerometer data and the temp/battery values and switch to DR_5 (otherways, you would exceed max. duty cycle time. I suppose you are in EU868 based upon your payload above).
    In the original firmware, open main.c and edit the following lines (in src/apps/classA):

    • Line 29, change to:
      #define APP_TX_DUTYCYCLE 5000
      This sends a package every 5 seconds instead of every 20 seconds

    • Line 40, change to
      This reduces the spreading factor, resulting in shorter transmission times. This is necessary so you don't overshoot the allowed duty cycle.

    • Line 52, change to
      #define LORAWAN_ADR_ON 0
      Adaptive data rate makes no sense with moving nodes, in fact, it can make things worse

    • Line 841, change to
      AppPort = 2
      You only want to send position data

    I'm just working on an alternative firmware where you can set App_Eui, App_Key, tracking mode, transmitted data and transmitting intervals over USB.

    Regards, Edi

  • Edi you are a star !.

    Thank you so much for your help.

    Without you i would have been stuck.



  • Ian, it was a pleasure to help you. Much success!

  • Hey Edi that worked fine.

    I would like to make one change that would improve it.

    As well at the GPS data being sent I would like the SNR data. Currently it is set to appPort=2.

    Can I send GPS and SNR data?


  • @ikilby Nice to hear!
    You always get the snr data in the meta data, so you don't need to modify anything.
    If you don't want to programm something, you could use ttnmapper.org, I think this would fit your needs exactly. Just add ttnmapper integration to your app. Then you can download nice csv from ttnmapper.org or get a map with your points (we had some thunderstorms, so I had to roam around the village with the fire fighters :) ). If you click the points, you get the RSSI and SNR data.
    Are you sure you are looking for SNR and not for RSSI?

  • @eiten said in RAK811 trackernode:

    Are you sure you are looking for SNR and not for RSSI?

    There is some formular to measure coverage? wich is best (snr/rss) or both?

  • @audorva Well, that's not too easy to answer. If you got a good rssi (singal strength) but much noise (low snr), you won't receive anything. Same if you got no noise (good snr) but the signal is too low (bad rssi). You can look at the link budget for a hint.

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