Restricting lmic to one SF and one channel

[MikeX7]

Hello,

I am going to be running a tiny private lorawan network for a few sensors I have and it wouldn't really make sense for me to buy full blown expensive gateways to service 2 or 3 sensors, so I will be using a gateway cobbled together from an ESP and one RFM95 module, which means this gateway will only be listening on one spreading factor and one channel.

For my nodes I would like to use the MCCI library with otaa. But, I need to somehow limit the mcci to only use one SF (9) and one channel, to make sure the gateway can hear it.

I realize that this is out of spec for lorawan, but since I can't afford to buy (and it wouldn't make sense in my case) to run full gateways (and there aren't any deployed where I live) this is the only option I have.

I had a look at the mcci source code and I could maybe hack it somehow together by changing all the frequencies in the config files and adjusting the random channel selections and such to all use the same SF and channel, but I am hoping that there is some cleaner way to do this.

Thank you!

[d-a-v]

I suggest checking the examples, there are calls to

        LMIC_setupChannel(0, ...)

Then you can

        for (int d = 1; d < 100; d++)
            LMIC_disableChannel(d);

[MikeX7]

I see, so first I should disable all of the channels with LMIC_disableChannel and then do this:

LMIC_setupChannel(0, 868100000, DR_RANGE_MAP(DR_SF9, DR_SF9), BAND_CENTI);

So that way it will enable only that one single channel with that one single SF? I'll try it out as soon as i get home, thanks. If it really is this easy then that would make me very happy.

[d-a-v]

Not sure if you can disable channel 0 then call LMIC_setupChannel(0).
Disabling from 1 (not 0) worked when I tried with an ESP single channel gateway.
I even put a wire/switch on one gpio of an avr lora sensor and its state at boot selected between a normal or a single channel setup.

[d-a-v]

Check also #33 which is where I now remember I got the info, especially the last message.

[terrillmoore]

@MikeX7 The LMIC does not allow "standard channels" in the region to be disabled or changed. (This was done as part of the compliance efforts -- these are all common code paths, and the compliance test tries to disable and change default channels from the MAC messages. It wasn't convenient to duplicate code, so I just locked things down to match the spec.) So single-channel support is going to be hard, as all regions have at least two channels. You're going to have to fork and edit the code, or use an older repo. Sorry!

[terrillmoore]

You can, however, reach into the LMIC databases directly... if you look at the EU-like settings in src/lmic/lmic.h, you'll see that all you really have to do is change the channel frequencies, the enable mask, and the DR masks. The channel frequencies are a funny 3-byte field, and the bottom 2 bits indicate the "band" (really they identify a group of channels with a common airtime duty-cycle requirement). There are three duty-cycles, 1% (CENTI), 0.1% (MILLI) and 10% (forget what it's called). This is ugly but doesn't require editing the library. It will probably require code changes as the library evolves, but not as much as hacking on the library directly!

[lnlp]

I am going to be running a tiny private lorawan network

So called Single Channel Packet Forwarders (SCPF) are not LoRaWAN gateways because not compliant with LoRaWAN requirements.

Not sure whichLoRaWAN network provider you want to use this with but on The Things Network (TTN) and many commercial LoRaWAN networks SCPF are not supported and not allowed. For more information check the LoRaWAN network providers (e.g. for TTN check their forum).

[mrx23dot]

You can just use the ping pong driver for RFM95, no need for full blown LMIC.