TTN Mapper node

Introduction

Small sketch to run a TTN Mapper node on an Adafruit Feather M0 Radio with LoRa Radio Module with an OLED FeatherWing.

See https://ttnmapper.org/ for more information about the TTN Mapper project.

Hardware requirements

• Adafruit Feather M0 Radio with LoRa Radio Module
• Adafruit OLED FeatherWing
• Female headers to stack the display on top of the Feather
• Optional: SMT uFL connector, pigtail and antenna
• Battery. Either a small 4.2/3.7V LiPo battery or a 5V source through the MicroUSB connector

To expose the RFM95 DIO1 to the M0, solder a bridge from the IO1 to Digital #11 (or any other free port).
The easiest is to solder this bridge on the FeatherWing.

Software requirements

Aside the Adafruit SAMD support you will need the following libraries:

• For the OLED FeatherWing:
  • Adafruit_SSD1306(1.1.2)
  • Adafruit-GFX-Library (1.2.5)
• For LoRaWan:
  • Arduino LMIC

Running the script

Copy ttn_secrets_template.h to ttn_secrets.h and set your Application Key and App EUI.
You also need to define a unique Device EUI -- as the Adafruit Feather does not have a serial number, take the one automatically generated in the TTN console.

By default, the node sends a message with * as payload every minute.

• You can change the send_packet_interval in ttn_mapper.cpp (Respect duty cycle!)
• To send battery voltage as Cayenne LPP instead of *, uncomment #define CAYENNE_LPP in ttn_mapper.cpp

Compile, upload and you should be good to go!

GPS Tracker and TTN Mapper Integration

To directly send the tracker location to the TTN Mapper integration you can add a GPS module and use the ttn-mapper-gps script.
You will need:

• Adafruit Ultimate GPS featherwing
• Male/Female headers to install the GPS between the MCU and the Display
• GPS antenna and pigtail

And the following libraries:

• Adafruit_GPS (1.0.3)
• Adafruit_ZeroTimer (2.0.0)
• Adafruit_ASFcore

Add the TTN Mapper integration to your application in the TTN Console and configure the Payload decoder with:

function Decoder(bytes, port) {
  // Decode an uplink message from a buffer
  // (array) of bytes to an object of fields.
  var decoded = {};
  if (port === 2) {
    // The port should match the port configured in `ttn_mapper.cpp`
    var i = 0;
    decoded.latitude = (bytes[i++]<<24) + (bytes[i++]<<16) + (bytes[i++]<<8) + bytes[i++];
    decoded.latitude = (decoded.latitude / 1e7) - 90;
    decoded.longitude = (bytes[i++]<<24) + (bytes[i++]<<16) + (bytes[i++]<<8) + bytes[i++];
    decoded.longitude = (decoded.longitude / 1e7) - 180;
    decoded.altitude = (bytes[i++]<<8) + bytes[i++];
    decoded.altitude = decoded.altitude - 0x7fff;
    decoded.hdop = (bytes[i++]<<8) + bytes[i++];
    decoded.hdop = decoded.hdop /10.0;
    if (bytes.length >= 14){
      decoded.voltage = ((bytes[i++]<<8)>>>0) + bytes[i++];
      decoded.voltage /= 100.0;
    }
  }
  return decoded;
}