Nasty OTAA connect
After getting basic connectivity for my RAK3172 test rig sorted I wanted to see if I could get the device connected to The Things Network(TTN) via the RAK7246G LPWAN Developer Gateway on my bookcase.
My Over the Air Activation (OTAA) implementation is very “nasty” I have assumed that there would be no timeouts or failures and I only send one BCD message “48656c6c6f204c6f526157414e” which is “hello LoRaWAN”.
The code just sequentially steps through the necessary configuration to join the TTN network with a suitable delay after each command is sent.
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// Copyright (c) September 2021, devMobile Software
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namespace devMobile.IoT.NetCore.RAK3172.NetworkJoinOTAA
{
using System;
using System.Diagnostics;
using System.IO.Ports;
using System.Threading;
public class Program
{
private const string SerialPortId = "/dev/ttyS0";
private const string AppEui = "...";
private const string AppKey = "...";
private const byte MessagePort = 1;
private const string Payload = "A0EEE456D02AFF4AB8BAFD58101D2A2A"; // Hello LoRaWAN
public static void Main()
{
string response;
Debug.WriteLine("devMobile.IoT.NetCore.Rak3172.NetworkJoinOTAA starting");
Debug.WriteLine(String.Join(",", SerialPort.GetPortNames()));
try
{
using (SerialPort serialPort = new SerialPort(SerialPortId))
{
// set parameters
serialPort.BaudRate = 9600;
serialPort.DataBits = 8;
serialPort.Parity = Parity.None;
serialPort.StopBits = StopBits.One;
serialPort.Handshake = Handshake.None;
serialPort.ReadTimeout = 5000;
serialPort.NewLine = "\r\n";
serialPort.Open();
// clear out the RX buffer
response = serialPort.ReadExisting();
Debug.WriteLine($"RX :{response.Trim()} bytes:{response.Length}");
Thread.Sleep(500);
// Set the Working mode to LoRaWAN
Console.WriteLine("Set Work mode");
serialPort.WriteLine("AT+NWM=1");
// Read the blank line
response = serialPort.ReadLine();
// Read the response
response = serialPort.ReadLine();
Debug.WriteLine($"RX :{response.Trim()} bytes:{response.Length}");
// Set the Region to AS923
Console.WriteLine("Set Region");
serialPort.WriteLine("AT+BAND=8-1");
// Read the blank line
response = serialPort.ReadLine();
// Read the response
response = serialPort.ReadLine();
Debug.WriteLine($"RX :{response.Trim()} bytes:{response.Length}");
// Set the JoinMode
Console.WriteLine("Set Join mode");
serialPort.WriteLine("AT+NJM=1");
// Read the blank line
response = serialPort.ReadLine();
// Read the response
response = serialPort.ReadLine();
Debug.WriteLine($"RX :{response.Trim()} bytes:{response.Length}");
// Set the appEUI
Console.WriteLine("Set App Eui");
serialPort.WriteLine($"AT+APPEUI={AppEui}");
// Read the blank line
response = serialPort.ReadLine();
// Read the response
response = serialPort.ReadLine();
Debug.WriteLine($"RX :{response.Trim()} bytes:{response.Length}");
// Set the appKey
Console.WriteLine("Set App Key");
serialPort.WriteLine($"AT+APPKEY={AppKey}");
// Read the blank line
response = serialPort.ReadLine();
// Read the response
response = serialPort.ReadLine();
Debug.WriteLine($"RX :{response.Trim()} bytes:{response.Length}");
// Set the Confirm flag
Console.WriteLine("Set Confirm off");
serialPort.WriteLine("AT+CFM=0");
// Read the blank line
response = serialPort.ReadLine();
// Read the response
response = serialPort.ReadLine();
Debug.WriteLine($"RX :{response.Trim()} bytes:{response.Length}");
// Join the network
Console.WriteLine("Start Join");
serialPort.WriteLine("AT+JOIN=1:0:10:2");
// Read the blank line
response = serialPort.ReadLine();
// Read the Result
response = serialPort.ReadLine();
Debug.WriteLine($"RX :{response.Trim()} bytes:{response.Length}");
Thread.Sleep(10000);
// Read the +EVT:JOINED
response = serialPort.ReadLine();
Debug.WriteLine($"RX :{response.Trim()} bytes:{response.Length}");
while (true)
{
Console.WriteLine("Sending");
serialPort.WriteLine($"AT+SEND={MessagePort}:{Payload}");
// Read the blank line
response = serialPort.ReadLine();
// Read the result
Console.WriteLine("Send result");
response = serialPort.ReadLine();
Debug.WriteLine($"RX :{response.Trim()} bytes:{response.Length}");
Thread.Sleep(300000);
}
}
}
catch (Exception ex)
{
Debug.WriteLine(ex.Message);
}
}
}
}
The code is not suitable for production but it confirmed my software and hardware configuration worked.

In the Visual Studio 2019 debug output I could see messages getting sent and then after a short delay they were visible in the TTN console.

The RAK3172 command format is quite different from other modules I have used e.g. Requesting the firmware version information
- TX- AT+VER=?
- RX- Blank Line
- RX- V1.0.2
- RX- OK
Requesting the APPEUI
- TX- AT+APPEUI=?
- RX- 1122334455667788
- RX- Blank line
- RX- OK
I think the RAK3172 module ships with a default DEVEUI so in this code and my library I have assumed it will be configured as part of a “provisioning” process.
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