Needed parts

The needed hardware parts are:

• Adafruit Feather 32u4 RFM95 LoRa
• Adafruit Ultimate GPS FeatherWing
• 86mm wire for antenna
• a housing
• LiPo battery 
• optinal: CR1220 for RTC battery backup

Needed software:

• Arduino IDE
• TinyGPS
• Arduino LMIC by Matthijs Kooijman
• Arduino Sketch (Sample Code from Pieter Hensen)

Build the hardware

At first we have to preperate the Adafruit 32u4. Connect PIN6 from the Adafruit with IO1 of the RFM95 module. Just solder in a little wire. Next you have to connect an Antenna to the ANT Port. I used a 86mm wire Antenna. Then solder in the connector strips for connecting the Feather Wing.  

Next comes the Wing. Solder in the socket strips and plug it into the 32u4.

Uploading the Arduino sketch

You find my sketch on GitHub. You only have to edit your keys an the device address. I used sample Code from Pieter Hensen. The sketch uses TinyGPS and the Arduino LMIC-Library, so you have to add them to the Arduino library. After the upload is finished, the nodes sends his data to TTN.

Preperations on TTN side

The tracker will send an encoded payload, so we have to configure an decoder on TTN side. I took the code from this forum post.

Insert the following code under Applications >> Application-Name >> Payload Formats >> Decoder

function Decoder(b, port) {

// Amsterdam: 52.3731, 4.8924 = MSB 07FDD3 00BF1C, LSB D3FD07 1CBF00

// La Paz: -16.4896, -68.1192 = MSB FD7BE0 F59B18, LSB E07BFD 189BF5

// New York: 40.7127, -74.0059 = MSB 063657 F4B525, LSB 573606 25B5F4

// Sidney: -33.8688, 151.2092 = MSB FAD500 17129C, LSB 00D5FA 9C1217

// LSB, Least Significant Bit/Byte first! Your node likely sends MSB instead.

// Sign-extend the 3rd and 6th bytes into a 4th and 8th byte:

var lat = (b[0] | b[1]<<8 | b[2]<<16 | (b[2] & 0x80 ? 0xFF<<24 : 0)) / 10000;

var lng = (b[3] | b[4]<<8 | b[5]<<16 | (b[5] & 0x80 ? 0xFF<<24 : 0)) / 10000;

return {

location: {

lat: lat,

lng: lng

},

love: "TTN payload functions"

};

}

Now you will see your received coordinates under Data.

Building a flow for Node-RED

I use Node-RED  location data parsing and storing it into an InfluxDB. I want to use Grafana for track visualization so i have to add a geohash.

You can download the Flow from GitHub.

Track visualisation with Grafana

I use this Grafana plugin form Teppo Kurki.  You can install with the following commands:

cd /var/lib/grafana/plugins/

wget https://github.com/tkurki/grafana-track-map/archive/master.zip

unzip master.zip cd grafana-track-map-master/

npm install

npm install -g grunt

grunt

systemctl restart grafana-server

Now we cann add a panel with this map plugin. Under metrics we have to define the database query. You have to select two values, one dummy as alias value and the geohashes as alias geohash.

The map view does not support  trackpoint highlighting. We have to add anaother panel. I used the RSSI and SNR data for another panel. Moving over the datapoints in this new panel, will highlight the GPS waypoints, so you can follow your GPS track.

Two other solutions are described here:

https://flows.nodered.org/flow/1aab1d44e387da96b3fe (possible to show the last x waypoints)

https://flows.nodered.org/node/node-red-contrib-web-worldmap (only updates when opened)