How can I make one Conduit talk to another over LoRa?

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  • May 23, 2018 at 4:54 pm #23612
    Adam Haun
    Participant

    For my application, I need a cellular gateway that can use LoRa as a backup network. I’d like to use class C multicasting to create a LoRa mesh network. My problem is, the Conduits don’t receive each other’s packets. This forum post suggests that I could modify the packet forwarder to change this by “[reversing] the IQ setting”. I searched the gateway’s configuration files and dug through the packet forwarder and LoRa gateway code in the Semtech Git repository, but I didn’t see any obvious filters or IQ settings. The closest thing I found was an option to invert the signal polarity, which didn’t help.

    What prevents one Conduit gateway from hearing another’s LoRa packets? And how can I subvert this mechanism so that two Conduits can talk to each other?

    May 24, 2018 at 7:02 am #23614
    Jason Reiss
    Keymaster

    You have found the correct setting in “ipol” of the packet forwarder protocol.
    https://github.com/Lora-net/packet_forwarder/blob/master/PROTOCOL.TXT

    Using this utility a packet can be received by another gateway running the packet forwarder. The utility sends packets with ipol set to false with an option (-i) to enable inverted polarity.
    admin@mtcdt:/opt/lora/gateway-utils# ./util_tx_test -f 902.3 -r 1257 -b125 -s 12 -c 1 8 -z 24 -k 0 -p27

    Other than the ipol setting, the frequency, spreading factory and bandwidth must be set correctly to a channel the conduit is listening for.
    There are 8 – 125 kHz channels, one 250 or 500 kHz channel and one FSK channel.

    May 24, 2018 at 4:59 pm #23624
    Adam Haun
    Participant

    Excellent! Thank you for the information, Jason. I’ll try to get this working. One question, though — my Conduit is an MTCDT-H5, and seems to have a USB connection to the LoRa module. The gateway’s util_tx_test doesn’t seem to work with a USB connection. Is there another version of the utility that works with my gateway?

    Thanks,
    -Adam

    May 25, 2018 at 6:17 am #23629
    Jason Reiss
    Keymaster

    Sending this json with a binary header to the down port of the packet forwarder should also work. The PROTOCOL.TXT file referenced above provides the info needed for the header.
    {"txpk":{"codr":"4/5","data":"oFxUlwEQRAAB8UObZx4=","datr":"SF8BW125",,"freq":921.9,"ipol":false,"modu":"LORA","ncrc":true,"powe":20,"rfch":0,"size":14,"imme":true}}

    Try to install the usb gateway utils.

    opkg update
opkg install lora-gateway-usb-utils

    This will create directory /opt/lora

    If opkg cannot connect to feed you can update the url in the following file
    Check /etc/opkgd/mlinux-feed.conf

    To find the mlinux version
    cat /etc/issue

    A list of feed paths are available here
    http://multitech.net/mlinux/feeds/

    May 25, 2018 at 3:30 pm #23637
    Adam Haun
    Participant

    It works! Thanks, Jason, that was exactly what I needed!

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