Depolying a TTN LoRa Gateway

I’ve been meaning to get round to this ever since the Pi Supply Kickstarter delivered my LoRa Gateway HAT and the LoRa Node pHAT.

They have been sat in their boxes waiting until I had some spare time (and I’d finally finished moving a few things around to free up a spare Pi).

LoRa Gateway on a Pi 3

LoRa is a long range, low bandwidth radio system that uses the unlicensed spectrum. When combined with the higher level LoRaWAN protocol it makes great IoT platform for low power devices that want to send low volumes of data in places where there is no WiFi coverage and can’t justify the cost of a cellular connection.

LoRaWAN allows you to deploy a collection of Gateway devices that can act as receivers for a large number of deployed devices. These gateways then forward on messages to central point for processing.

The Things Network

A group called The Things Network run a LoRaWAN deployment. They are aiming for as large a coverage area as possible. To do this they allow users to deploy their own gateways and join these to the network. By joining the network you get to use everybody elses gateways in exchange for letting other people use yours.

Setting up the Gateway

This was particularly easy. I just had to download an image and flash it to a SD card. Stick that into the pi along with an ethernet cable and some power.

After the pi boots up you point your browser at http://iotloragateway.local and fill in a couple of values generated when I registered the gateway on the TTN site and that was it. The gateway is now up and running and ready to send/receive packets from any devices in range.

Testing

In order to test the gateway I need to set up a Pi Zero with the LoRa Node pHAT. This was a little trickier, but not much.

Fist I had to disable the Linux serial console, this can be done using the raspi-config command. I also had to add dtoverlay=pi3-miniuart-bt /boot/config.txt.

That was all that was needed to get the hardware configured, as for the software there is a rak811 python package that supplies the api and utilities to work with pHAT.

I now needed to declare an application on The Things Network site, this is how messages get routed to be processes. Taking the values for this application I could now write the following helloWorld.py

#!/usr/bin/env python3
from rak811 import Mode, Rak811

lora = Rak811()
lora.hard_reset()
lora.mode = Mode.LoRaWan
lora.band = 'EU868'
lora.set_config(app_eui='xxxxxxxxx',
                app_key='xxxxxxxxxxxx')
lora.join_otaa()
lora.dr = 5
lora.send('Hello world')
lora.close()

Which can then be seen arriving in The Things Network console.

Data arriving and being displayed in The Things Network console.

And I can subscribe directly to that data feed via MQTT:

$ mosquitto_sub -h eu.thethings.network -u 'lora-app1-hardill-me-uk' -P 'xxxxxxxxx' -v -t '+/devices/+/up'
{
  "app_id": "lora-app1-hardill-me-uk",
  "dev_id": "test-lora-pi-zero",
  "hardware_serial": "323833356E387901",
  "port": 1,
  "counter": 0,
  "is_retry": true,
  "payload_raw": "SGVsbG8gd29ybGQ=",
  "metadata": {
    "time": "2019-08-10T15:45:07.568449769Z",
    "frequency": 867.5,
    "modulation": "LORA",
    "data_rate": "SF7BW125",
    "airtime": 61696000,
    "coding_rate": "4/5",
    "gateways": [
      {
        "gtw_id": "lora-gw1-hardill-me-uk",
        "gtw_trusted": true,
        "timestamp": 910757708,
        "time": "2019-08-10T15:45:07Z",
        "channel": 5,
        "rssi": -91,
        "snr": 7.75,
        "rf_chain": 0,
        "latitude": 51.678905,
        "longitude": -2.3549008,
        "location_source": "registry"
      }
    ]
  }
}

Next Steps

First up will be to get a better antenna for the gateway and to move the whole things up in the attic, from there it should get a good view north out towards the River Severn. After that I want to get a small battery powered LoRa/GPS board, like a TTGO T-Beam and ride round on my bike to get a feel for what the range/coverage actually is.

I’ll also be keeping an eye on the stats from the gateway to see if anybody else near by is deploying TTN LoRaWAN devices.