The gateway
A Raspberry Pi, a concentrator card and an antenna on the roof — what turns that into a LoRaWAN gateway.
My LoRaWAN gateway is not a finished box but three parts that have to agree with each other: a small computer, a radio card, and an antenna hung high enough.
What is in it
Raspberry Pi 3B+ — the computer. It does no radio itself; it takes what the radio card receives and passes it on. This size is plenty for that, and it draws little power, which matters when a device runs for years.
IMST iC880A — the concentrator card, 868 MHz, connected over SPI. It is the actual radio part and the reason a gateway can do more than a single radio chip: it listens on eight channels at once, and on all spreading factors at the same time. A sensor transmitting somewhere out in a field has to coordinate with nobody — the gateway simply hears it.
ch2i adapter board — the link between the two. Not strictly necessary, but it saves soldering flying wires and brings along things that turn out to be very useful in operation:
- four LEDs showing the state without anyone having to log in
- a 1.3" OLED displaying address, state and counters
- BME280 for temperature, humidity and pressure inside the enclosure
- a 1-Wire temperature sensor for the enclosure warmth
- a reset button
External outdoor antenna. The part that gives the most and costs the least. With LoRaWAN, height decides more than transmit power: a gateway with a good view hears devices kilometres away, the same gateway on a shelf hears the neighbour.
Why this combination
It is the best-documented one there is for a home build. Raspberry Pi plus iC880A has been the combination that guides, enclosures and install scripts refer to for years — and when something gets stuck, somebody has had it before you.
The price: it is a kit, not an appliance. What runs here runs because somebody put it together and keeps looking after it.
What it is not
The gateway is not a network. It is an antenna with an internet connection: it hears radio packets and passes them on to the network servers, which decide where they belong. It knows none of the devices, decrypts nothing and stores nothing — more on that under LoRaWAN explained.
Who it delivers to
Not to one network server but to more than four foreign ones at the same time — among them The Things Network V3. Who the others are does not belong on this page; they are networks that get something out of the location.
For the gateway this is no extra work. The same received packet goes to every server on the list, and each one checks for itself whether one of its devices was meant. Whoever can do nothing with it discards it — and reading it is possible only for whoever holds the key, which is never here.
That number is the reason for the choice of packet forwarder: the previous one could serve four servers at most. More on that under Software.