nanoFramework RAK811 LoRaWAN library Part1

Invalidating the warranty

Over the last couple of days I have been working on a nanoFramework C# library for my RAK811 LPWAN Evaluation Board(EVB) from RAK Wireless which I have been using with an Arduino Uno R3 device. My initial test rig is based on an STM32F691DISCOVERY board which has Arduino Uno R3 format socket for the EVB.

My first step was to check what serial ports were available (COM5 & COM6) on the STM32F691Discovery and what pins they were connected to. (COM6 Arduino D0 & D1). Then check that these would work with the EVB pin assignments.

RAK 811 EVB schematic pg1
RAK 811 EVB schematic pg2

My first test was was a simple loopback based on the nanoFramework samples Serial Communications example.

STM32F691Discovery with jumper loopback
STM32F691Discovery with jumper loopback
//---------------------------------------------------------------------------------
// Copyright (c) June 2020, devMobile Software
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
//---------------------------------------------------------------------------------
//#define ESP32_WROOM   //nanoff --target ESP32_WROOM_32 --serialport COM4 --update
//#define NETDUINO3_WIFI   // nanoff --target NETDUINO3_WIFI --update
//#define MBN_QUAIL // nanoff --target MBN_QUAIL --update
//#define ST_NUCLEO64_F091RC // nanoff --target ST_NUCLEO64_F091RC --update
//#define ST_NUCLEO144_F746ZG //nanoff --target ST_NUCLEO144_F746ZG --update
#define ST_STM32F769I_DISCOVERY      // nanoff --target ST_STM32F769I_DISCOVERY --update 
namespace devMobile.IoT.Rak811.ShieldSerial
{
   using System;
   using System.Diagnostics;
   using System.Threading;
   using Windows.Devices.SerialCommunication;
   using Windows.Storage.Streams;

#if ESP32_WROOM_32_LORA_1_CHANNEL
   using nanoFramework.Hardware.Esp32;
#endif

   public class Program
   {
#if ESP32_WROOM
      private const string SerialPortId = "";
#endif
#if NETDUINO3_WIFI
      private const string SpiBusId = "";
#endif
#if MBN_QUAIL
      private const string SpiBusId = "";
#endif
#if ST_NUCLEO64_F091RC
      private const string SpiBusId = "";
#endif
#if ST_NUCLEO144_F746ZG
      private const string SpiBusId = "";
#endif
#if ST_STM32F429I_DISCOVERY
      private const string SpiBusId = "";
#endif
#if ST_STM32F769I_DISCOVERY
      private const string SerialPortId = "COM6";
#endif

      public static void Main()
      {
         SerialDevice serialDevice;

         Debug.WriteLine("devMobile.IoT.Rfm9x.ShieldSerial starting");

         Debug.WriteLine(Windows.Devices.SerialCommunication.SerialDevice.GetDeviceSelector());

         try
         {
            // set GPIO functions for COM2 (this is UART1 on ESP32)
            #if ESP32_WROOM
               Configuration.SetPinFunction(Gpio.IO04, DeviceFunction.COM2_TX);
               Configuration.SetPinFunction(Gpio.IO05, DeviceFunction.COM2_RX);
            #endif
            serialDevice = SerialDevice.FromId(SerialPortId);

            // set parameters
            serialDevice.BaudRate = 9600;
            serialDevice.Parity = SerialParity.None;
            serialDevice.StopBits = SerialStopBitCount.One;
            serialDevice.Handshake = SerialHandshake.None;
            serialDevice.DataBits = 8;

            serialDevice.ReadTimeout = new TimeSpan(0, 0, 30);
            serialDevice.WriteTimeout = new TimeSpan(0, 0, 4);

            DataWriter outputDataWriter = new DataWriter(serialDevice.OutputStream);

            #if SERIAL_SYNC_READ
               DataReader inputDataReader = new DataReader(serialDevice.InputStream);
            #else
               serialDevice.DataReceived += SerialDevice_DataReceived;
            #endif

            // set a watch char to be notified when it's available in the input stream
            serialDevice.WatchChar = '\n';

            while (true)
            {
               uint bytesWritten = outputDataWriter.WriteString("at+version\r\n");
               Debug.WriteLine($"TX: {outputDataWriter.UnstoredBufferLength} bytes to output stream.");

               // calling the 'Store' method on the data writer actually sends the data
               uint txByteCount = outputDataWriter.Store();
               Debug.WriteLine($"TX: {txByteCount} bytes via {serialDevice.PortName}");

#if SERIAL_SYNC_READ
               uint bytesRead = inputDataReader.Load(50);

               Debug.WriteLine($"RXs :{bytesRead} bytes read from {serialDevice.PortName}");

               if (bytesRead > 0)
               {
                  String response = inputDataReader.ReadString(bytesRead);
                  Debug.WriteLine($"RX sync:{response}");
               }
#endif

               Thread.Sleep(20000);
            }
         }
         catch (Exception ex)
         {
            Debug.WriteLine(ex.Message);
         }
      }

      private static void SerialDevice_DataReceived(object sender, SerialDataReceivedEventArgs e)
      {
         switch(e.EventType)
         {
            case SerialData.Chars:
               //Debug.WriteLine("RX SerialData.Chars");
               break;

            case SerialData.WatchChar:
               Debug.WriteLine("RX: SerialData.WatchChar");
               SerialDevice serialDevice = (SerialDevice)sender;

               using (DataReader inputDataReader = new DataReader(serialDevice.InputStream))
               {
                  inputDataReader.InputStreamOptions = InputStreamOptions.Partial;

                  // read all available bytes from the Serial Device input stream
                  uint bytesRead = inputDataReader.Load(serialDevice.BytesToRead);

                  Debug.WriteLine($"RXa: {bytesRead} bytes read from {serialDevice.PortName}");

                  if (bytesRead > 0)
                  {
                     String response = inputDataReader.ReadString(bytesRead);
                     Debug.WriteLine($"RX:{response}");
                  }
               }
               break;
            default:
               Debug.Assert(false, $"e.EventType {e.EventType} unknown");
               break;
         }
      }
   }
}

After some tinkering I could successfully transmit and receive a string.

The next step was to connect my EVB and sent the AT Command to request the LoRaWAN module version information

STM32F691Discovery with EVB connected with Jumpers
STM32F691Discovery with EVB connected with Jumpers
The thread '<No Name>' (0x2) has exited with code 0 (0x0).
devMobile.IoT.Rfm9x.ShieldSerial starting
COM5,COM6
TX: 12 bytes to output stream.
TX: 12 bytes via COM6
RX: SerialData.WatchChar
RXa: 19 bytes read from COM6
RX:OK V3.0.0.13.H.T3

TX: 12 bytes to output stream.
TX: 12 bytes via COM6
RX: SerialData.WatchChar
RXa: 19 bytes read from COM6
RX:OK V3.0.0.13.H.T3

The response was the same as I got with the RAK Serial Port Tool which was positive.

Version number check with RAK Serial Port tool

I need to do some more digging into how serialDevice.WatchChar = ‘\n’ works for synchronous reads.

Plus removing R17 & R19 there is no interaction with D11 & D10 which are normally used by the Serial Peripheral Interface(SPI) port so I can plug the shield directly into the STM32F691Discovery board.

My plan was to get an initial version of the library working with the STM32F691Discovery, then port it to the Netduino 3 Wifi (possible serial port pin issues) , ST_NUCLEO144_F746ZG, and ST_NUCLEO64_F091RC (possible issues with available flash).

One thought on “nanoFramework RAK811 LoRaWAN library Part1

  1. Pingback: nanoFramework RAK811 LoRaWAN library Part2 | devMobile's blog

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