RFM69 hat library Part5

Receive Basic: Rasmatic/RFM69-Arduino-Library

Next step was to extend my code to receive packets (no addressing or encryption). Initially I didn’t receive any messages as I had neglected to configure the variable length flag (RegPacketConfig bit 7) and had a typo in the RegRxBw register configuration.

/*
 Copyright ® 2019 June devMobile Software, All Rights Reserved

 MIT License

 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
 in the Software without restriction, including without limitation the rights
 to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 copies of the Software, and to permit persons to whom the Software is
 furnished to do so, subject to the following conditions:

 The above copyright notice and this permission notice shall be included in all
 copies or substantial portions of the Software.

 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 SOFTWARE

*/
namespace devMobile.IoT.Rfm69Hcw.ReceiveBasic
{
	using System;
	using System.Diagnostics;
	using System.Runtime.InteropServices.WindowsRuntime;
	using System.Text;
	using System.Threading.Tasks;
	using Windows.ApplicationModel.Background;
	using Windows.Devices.Spi;
	using Windows.Devices.Gpio;

	public sealed class Rfm69HcwDevice
	{
		private SpiDevice Rfm69Hcw;
		private const byte RegisterAddressReadMask = 0X7f;
		private const byte RegisterAddressWriteMask = 0x80;

		public Rfm69HcwDevice(int chipSelectPin, int resetPin)
		{
			SpiController spiController = SpiController.GetDefaultAsync().AsTask().GetAwaiter().GetResult();
			var settings = new SpiConnectionSettings(chipSelectPin)
			{
				ClockFrequency = 500000,
				Mode = SpiMode.Mode0,
			};

			// Factory reset pin configuration
			GpioController gpioController = GpioController.GetDefault();
			GpioPin resetGpioPin = gpioController.OpenPin(resetPin);
			resetGpioPin.SetDriveMode(GpioPinDriveMode.Output);
			resetGpioPin.Write(GpioPinValue.Low);
			Task.Delay(100);
			resetGpioPin.Write(GpioPinValue.High);
			Task.Delay(100);
			resetGpioPin.Write(GpioPinValue.Low);

			Task.Delay(100);

			Rfm69Hcw = spiController.GetDevice(settings);
		}

		public Byte RegisterReadByte(byte address)
		{
			byte[] writeBuffer = new byte[] { address &= RegisterAddressReadMask };
			byte[] readBuffer = new byte[1];
			Debug.Assert(Rfm69Hcw != null);

			Rfm69Hcw.TransferSequential(writeBuffer, readBuffer);

			return readBuffer[0];
		}

		public ushort RegisterReadWord(byte address)
		{
			byte[] writeBuffer = new byte[] { address &= RegisterAddressReadMask };
			byte[] readBuffer = new byte[2];
			Debug.Assert(Rfm69Hcw != null);

			Rfm69Hcw.TransferSequential(writeBuffer, readBuffer);

			return (ushort)(readBuffer[1] + (readBuffer[0] << 8));
		}

		public byte[] RegisterRead(byte address, int length)
		{
			byte[] writeBuffer = new byte[] { address &= RegisterAddressReadMask };
			byte[] readBuffer = new byte[length];
			Debug.Assert(Rfm69Hcw != null);

			Rfm69Hcw.TransferSequential(writeBuffer, readBuffer);

			return readBuffer;
		}

		public void RegisterWriteByte(byte address, byte value)
		{
			byte[] writeBuffer = new byte[] { address |= RegisterAddressWriteMask, value };
			Debug.Assert(Rfm69Hcw != null);

			Rfm69Hcw.Write(writeBuffer);
		}

		public void RegisterWriteWord(byte address, ushort value)
		{
			byte[] valueBytes = BitConverter.GetBytes(value);
			byte[] writeBuffer = new byte[] { address |= RegisterAddressWriteMask, valueBytes[0], valueBytes[1] };
			Debug.Assert(Rfm69Hcw != null);

			Rfm69Hcw.Write(writeBuffer);
		}

		public void RegisterWrite(byte address, [ReadOnlyArray()] byte[] bytes)
		{
			byte[] writeBuffer = new byte[1 + bytes.Length];
			Debug.Assert(Rfm69Hcw != null);

			Array.Copy(bytes, 0, writeBuffer, 1, bytes.Length);
			writeBuffer[0] = address |= RegisterAddressWriteMask;

			Rfm69Hcw.Write(writeBuffer);
		}

		public void RegisterDump()
		{
			Debug.WriteLine("Register dump");
			for (byte registerIndex = 0; registerIndex <= 0x3D; registerIndex++)
			{
				byte registerValue = this.RegisterReadByte(registerIndex);

				Debug.WriteLine("Register 0x{0:x2} - Value 0X{1:x2} - Bits {2}", registerIndex, registerValue, Convert.ToString(registerValue, 2).PadLeft(8, '0'));
			}
		}
	}


	public sealed class StartupTask : IBackgroundTask
	{
		private const int ChipSelectLine = 1;
		private const int ResetLine = 25;
		private Rfm69HcwDevice rfm69Device = new Rfm69HcwDevice(ChipSelectLine, ResetLine);

		const double RH_RF6M9HCW_FXOSC = 32000000.0;
		const double RH_RFM69HCW_FSTEP = RH_RF6M9HCW_FXOSC / 524288.0;

		public void Run(IBackgroundTaskInstance taskInstance)
		{
			//rfm69Device.RegisterDump();

			// regOpMode standby
			rfm69Device.RegisterWriteByte(0x01, 0b00000100);

			// BitRate MSB/LSB
			rfm69Device.RegisterWriteByte(0x03, 0x34);
			rfm69Device.RegisterWriteByte(0x04, 0x00);

			// Calculate the frequency accoring to the datasheett
			byte[] bytes = BitConverter.GetBytes((uint)(915000000.0 / RH_RFM69HCW_FSTEP));
			Debug.WriteLine("Byte Hex 0x{0:x2} 0x{1:x2} 0x{2:x2} 0x{3:x2}", bytes[0], bytes[1], bytes[2], bytes[3]);
			rfm69Device.RegisterWriteByte(0x07, bytes[2]);
			rfm69Device.RegisterWriteByte(0x08, bytes[1]);
			rfm69Device.RegisterWriteByte(0x09, bytes[0]);

			// RegRxBW
			rfm69Device.RegisterWriteByte(0x19, 0x2a);

			// Setup preamble length to 16 (default is 3) RegPreambleMsb RegPreambleLsb
			rfm69Device.RegisterWriteByte(0x2C, 0x0);
			rfm69Device.RegisterWriteByte(0x2D, 0x10);

			// RegSyncConfig Set the Sync length and byte values SyncOn + 3 custom sync bytes
			rfm69Device.RegisterWriteByte(0x2e, 0x90);

			// RegSyncValues1 thru RegSyncValues3
			rfm69Device.RegisterWriteByte(0x2f, 0xAA);
			rfm69Device.RegisterWriteByte(0x30, 0x2D);
			rfm69Device.RegisterWriteByte(0x31, 0xD4);

			// RegPacketConfig1 Variable length with CRC on
			rfm69Device.RegisterWriteByte(0x37, 0x90);

			rfm69Device.RegisterWriteByte(0x01, 0b00010000); // RegOpMode set ReceiveMode

			rfm69Device.RegisterDump();

			while (true)
			{
				// Wait until a packet is received, no timeouts in PoC
				Debug.WriteLine("Receive-Wait");
				byte IrqFlags = rfm69Device.RegisterReadByte(0x28); // RegIrqFlags2
				while ((IrqFlags & 0b00000100) == 0)  // wait until PayLoadReady set
				{
					Task.Delay(20).Wait();
					IrqFlags = rfm69Device.RegisterReadByte(0x28); // RegIrqFlags2
					//Debug.WriteLine(string.Format("RegIrqFlags {0}", Convert.ToString((byte)IrqFlags, 2).PadLeft(8, '0')));
					Debug.Write(".");
				}
				Debug.WriteLine("");

				// Rwad the length
				byte numberOfBytes = rfm69Device.RegisterReadByte(0x0); 

				// Allocate buffer for message
				byte[] messageBytes = new byte[numberOfBytes];

				for (int i = 0; i < numberOfBytes; i++)
				{
					messageBytes[i] = rfm69Device.RegisterReadByte(0x00); // RegFifo
				}

				string messageText = UTF8Encoding.UTF8.GetString(messageBytes);
				Debug.WriteLine("Received {0} byte message {1}", messageBytes.Length, messageText);

				Debug.WriteLine("Receive-Done");
			}
		}
	}
}

I modified the Arduino application to transmit a message (with a counter so I could spot dropped messages) every second

#include <SPI.h>
#include <stdio.h>
#include <RMRFM69.h>

#define SENDER_DETECT_PIN 4

RMRFM69 radio(SPI, 10, 2, 9);

byte counter = 0 ;

void setup() 
{
  Serial.begin(9600);

  pinMode(SENDER_DETECT_PIN, INPUT_PULLUP);  
  
  radio.Modulation     = FSK;
  radio.COB            = RFM69;
  radio.Frequency      = 915000;
  radio.OutputPower    = 10+18;          //10dBm OutputPower
  radio.PreambleLength = 16;             //16Byte preamble
  radio.FixedPktLength = false;          //packet in message which need to be send
  radio.CrcDisable     = false;          //CRC On
  radio.AesOn          = false;
  radio.SymbolTime     = 416000;         //2.4Kbps
  radio.Devation       = 35;             //35KHz for devation
  radio.BandWidth      = 100;            //100KHz for bandwidth
  radio.SyncLength     = 3;              //
  radio.SyncWord[0]    = 0xAA;
  radio.SyncWord[1]    = 0x2D;
  radio.SyncWord[2]    = 0xD4;

  radio.vInitialize();
  
  if (digitalRead(SENDER_DETECT_PIN) == LOW)
  {
    Serial.println("RX start");
    radio.vGoRx();
  }
  else
  {
    Serial.println("TX start");
    //radio.vGoTx();    
  }
  radio.dumpRegisters(Serial);
}

void loop() 
{
  char messageIn[128] = {""};
  char messageOut[32]= {"Hello world:"};

  if (digitalRead(SENDER_DETECT_PIN) == LOW)
  {
    if(radio.bGetMessage(messageIn)!=0)
    { 
      Serial.print("MessageIn:");
      Serial.println(messageIn);
    }    
  }
  else
  {  
    Serial.print("MessageOut:") ;
    itoa(counter,&messageOut[strlen( messageOut)],10);
    Serial.println(messageOut);
    if (!radio.bSendMessage(messageOut, strlen(messageOut)))
    {
      Serial.println("bSendMessage failed");
    }
    counter++;
    delay(1000);
  }
}
Arduino device in receive mode

With the Arduino device transmitting the debug output in Visual Studio looked like this. It does seem a bit odd that the “Receive-Wait” is slowly getting longer.

Register dump
Register 0x00 - Value 0X00 - Bits 00000000
Register 0x01 - Value 0X10 - Bits 00010000
…
Register 0x3c - Value 0X0f - Bits 00001111
Register 0x3d - Value 0X02 - Bits 00000010
Receive-Wait
The thread 0x990 has exited with code 0 (0x0).
Received 13 byte message Hello world:0
Receive-Done
Receive-Wait
.............................................
Received 13 byte message Hello world:1
Receive-Done
Receive-Wait
...........................................
Received 13 byte message Hello world:2
Receive-Done
Receive-Wait
............................................
Received 13 byte message Hello world:3
Receive-Done
Receive-Wait
............................................
Received 13 byte message Hello world:4
Receive-Done
Receive-Wait
.............................................
Received 13 byte message Hello world:5
Receive-Done
Receive-Wait
............................................
Received 13 byte message Hello world:6
Receive-Done
Receive-Wait
............................................

I ran the client for several hours and it didn’t appear to drop any messages. Next step is to covert the receive and transmit code to use interrupts.

RFM69 hat library Part4C

Transmit Basic: Rasmatic/RFM69-Arduino-Library

While I was searching for a suitable library on GitHub I downloaded the RFM-Arduino-Library by Rasmatic which had a link to sample library on the HopeRF website which I also downloaded.

/*
@author Tadeusz Studnik https://rasmatic.pl

MIT License
...

This library is a port of HopeRF's library:

https://www.hoperf.com/data/upload/back/20181122/HoepRF_HSP_V1.3.rar
*/

I made the minimum possible modifications to the C/C++ code to get it to compile, then to run on my Arduino Nano Radio Shield RFM69/95 device. I had to change the RFM69 DIO pin mode, the SPI config, and I added a method to dump all the registers.

/**********************************************************
**Name:     vInitialize
**Function: initialize rfm69 or rfm69c
**Input:    none
**Output:   none
**********************************************************/
void RMRFM69::vInitialize(void)
{
	pinMode (_csPin, OUTPUT);
	pinMode (_rstPin, OUTPUT);
	pinMode (_dio0Pin, INPUT_PULLDOWN); // Changed from INPUT_PULLDOWN

	digitalWrite(_csPin, HIGH);
	digitalWrite(_rstPin, LOW);
	
	vSpiInit();
	
	//�˿ڳ�ʼ�� for 32MHz
	FrequencyValue.Freq = (Frequency << 11) / 125; //Calc. Freq
	BitRateValue = (SymbolTime << 5) / 1000;	   //Calc. BitRate
	DevationValue = (Devation << 11) / 125;		   //Calc. Fdev
	BandWidthValue = bSelectBandwidth(BandWidth);

	vConfig();
	vGoStandby();
}
/**********************************************************
**Name:     vSpiInit
**Function: init SPI
**Input:    none
**Output:   none
**********************************************************/
void RMRFM69::vSpiInit()
{
	digitalWrite(_csPin, HIGH);
//	_spiPort->setFrequency(1000000); 
	_spiPort->setBitOrder(MSBFIRST);
	_spiPort->setDataMode(SPI_MODE0);
	_spiPort->begin();

}

void RMRFM69::dumpRegisters(Stream& out)
{
  for (int i = 0; i <= 0x3d; i++) {
    out.print("0x");
    out.print(i, HEX);
    out.print(": 0x");
    out.println(this->bSpiRead(i), HEX);
  }
}

I created an application based on the RFM69-ESP32-arduino-example which received messages.

#include <SPI.h>
#include <RMRFM69.h>

RMRFM69 radio(SPI, 10, 2, 9);

void setup() 
{
  Serial.begin(9600);
  
  radio.Modulation     = FSK;
  radio.COB            = RFM69;
  radio.Frequency      = 915000;
  radio.OutputPower    = 10+18;          //10dBm OutputPower
  radio.PreambleLength = 16;             //16Byte preamble
  radio.FixedPktLength = false;          //packet in message which need to be send
  radio.CrcDisable     = false;          //CRC On
  radio.AesOn          = false;
  radio.SymbolTime     = 416000;         //2.4Kbps
  radio.Devation       = 35;             //35KHz for devation
  radio.BandWidth      = 100;            //100KHz for bandwidth
  radio.SyncLength     = 3;              //
  radio.SyncWord[0]    = 0xAA;
  radio.SyncWord[1]    = 0x2D;
  radio.SyncWord[2]    = 0xD4;

  radio.vInitialize();

  radio.dumpRegisters(Serial);
  radio.vGoRx();

  Serial.println("Start RX...");
}

void loop() 
{
  char messageIn[128] = {""};
  byte messageOut[] = {"Hello world"};

  if(radio.bGetMessage(messageIn)!=0)
  { 
    Serial.print("MessageIn:");
    Serial.print(messageIn);
    Serial.println();
  }    
}

The application started up after I sorted out the RFM69 chip select, interrupt and reset pin numbers.

20:03:56.574 -> 0x0: 0x0
20:03:56.608 -> 0x1: 0x4
20:03:56.608 -> 0x2: 0x0
20:03:56.608 -> 0x3: 0x34
20:03:56.643 -> 0x4: 0x0
20:03:56.643 -> 0x5: 0x2
20:03:56.643 -> 0x6: 0x3D
20:03:56.643 -> 0x7: 0xE4
20:03:56.677 -> 0x8: 0xC0
20:03:56.677 -> 0x9: 0x0
20:03:56.677 -> 0xA: 0x41
20:03:56.710 -> 0xB: 0x40
20:03:56.710 -> 0xC: 0x2
20:03:56.710 -> 0xD: 0x92
20:03:56.745 -> 0xE: 0xF5
20:03:56.745 -> 0xF: 0x20
20:03:56.745 -> 0x10: 0x24
20:03:56.779 -> 0x11: 0x9C
20:03:56.779 -> 0x12: 0x5
20:03:56.813 -> 0x13: 0xF
20:03:56.813 -> 0x14: 0x40
20:03:56.813 -> 0x15: 0xB0
20:03:56.846 -> 0x16: 0x7B
20:03:56.846 -> 0x17: 0x9B
20:03:56.846 -> 0x18: 0x88
20:03:56.880 -> 0x19: 0x2A
20:03:56.880 -> 0x1A: 0x2A
20:03:56.880 -> 0x1B: 0x78
20:03:56.880 -> 0x1C: 0x80
20:03:56.914 -> 0x1D: 0x6
20:03:56.914 -> 0x1E: 0x10
20:03:56.947 -> 0x1F: 0x0
20:03:56.947 -> 0x20: 0x0
20:03:56.947 -> 0x21: 0x0
20:03:56.981 -> 0x22: 0x0
20:03:56.981 -> 0x23: 0x2
20:03:56.981 -> 0x24: 0xFF
20:03:57.015 -> 0x25: 0x0
20:03:57.015 -> 0x26: 0xF7
20:03:57.049 -> 0x27: 0x80
20:03:57.049 -> 0x28: 0x0
20:03:57.049 -> 0x29: 0xFF
20:03:57.083 -> 0x2A: 0x0
20:03:57.083 -> 0x2B: 0x0
20:03:57.083 -> 0x2C: 0x0
20:03:57.118 -> 0x2D: 0x10
20:03:57.118 -> 0x2E: 0x90
20:03:57.152 -> 0x2F: 0xAA
20:03:57.152 -> 0x30: 0x2D
20:03:57.152 -> 0x31: 0xD4
20:03:57.152 -> 0x32: 0x0
20:03:57.186 -> 0x33: 0x0
20:03:57.186 -> 0x34: 0x0
20:03:57.186 -> 0x35: 0x0
20:03:57.219 -> 0x36: 0x0
20:03:57.219 -> 0x37: 0x90
20:03:57.219 -> 0x38: 0x40
20:03:57.253 -> 0x39: 0x0
20:03:57.253 -> 0x3A: 0x0
20:03:57.253 -> 0x3B: 0x0
20:03:57.288 -> 0x3C: 0x1
20:03:57.288 -> 0x3D: 0x0
20:03:57.322 -> Start RX...

I then manually set the RFM69HCW Radio Bonnet registers to match the Arduino device.

public sealed class StartupTask : IBackgroundTask
{
	private const int ChipSelectLine = 1;
	private const int ResetLine = 25;
	private Rfm69HcwDevice rfm69Device = new Rfm69HcwDevice(ChipSelectLine, ResetLine);

	const double RH_RF6M9HCW_FXOSC = 32000000.0;
	const double RH_RFM69HCW_FSTEP = RH_RF6M9HCW_FXOSC / 524288.0;

	const byte NetworkID = 100;
	const byte NodeAddressFrom = 0x03;
	const byte NodeAddressTo = 0x02;

	public void Run(IBackgroundTaskInstance taskInstance)
	{
		//rfm69Device.RegisterDump();

		// regOpMode standby
		rfm69Device.RegisterWriteByte(0x01, 0b00000100);

		// BitRate MSB/LSB
		rfm69Device.RegisterWriteByte(0x03, 0x34);
		rfm69Device.RegisterWriteByte(0x04, 0x00);

		// Frequency deviation
		rfm69Device.RegisterWriteByte(0x05, 0x02);
		rfm69Device.RegisterWriteByte(0x06, 0x3d);
			
		// Calculate the frequency accoring to the datasheett
		byte[] bytes = BitConverter.GetBytes((uint)(915000000.0 / RH_RFM69HCW_FSTEP));
		Debug.WriteLine("Byte Hex 0x{0:x2} 0x{1:x2} 0x{2:x2} 0x{3:x2}", bytes[0], bytes[1], bytes[2], bytes[3]);
		rfm69Device.RegisterWriteByte(0x07, bytes[2]);
		rfm69Device.RegisterWriteByte(0x08, bytes[1]);
		rfm69Device.RegisterWriteByte(0x09, bytes[0]);

		// RegRxBW
		rfm69Device.RegisterWriteByte(0x19, 0x55);
		// RegAfcBw
		rfm69Device.RegisterWriteByte(0x1A, 0x8b);
		// RegOokPeak
		rfm69Device.RegisterWriteByte(0x1B, 0x40);

		// Setup preamble length to 16 (default is 3)
		rfm69Device.RegisterWriteByte(0x2C, 0x0);
		rfm69Device.RegisterWriteByte(0x2D, 0x10);
	
		// Set the Sync length and byte values SyncOn + 3 custom sync bytes
		rfm69Device.RegisterWriteByte(0x2e, 0x90);

		rfm69Device.RegisterWriteByte(0x2f, 0xAA);
		rfm69Device.RegisterWriteByte(0x30, 0x2D);
		rfm69Device.RegisterWriteByte(0x31, 0xD4);

		// RegPacketConfig1 changed for Variable length after 9:00PM vs 10:00PM fail
		rfm69Device.RegisterWriteByte(0x37, 0x90);
		//rfm69Device.RegisterWriteByte(0x38, 0x14);

		rfm69Device.RegisterDump();
	
		while (true)
		{
			// Standby mode while loading message into FIFO
			rfm69Device.RegisterWriteByte(0x01, 0b00000100);
			byte[] messageBuffer = UTF8Encoding.UTF8.GetBytes(" hello world " + DateTime.Now.ToLongTimeString());
			messageBuffer[0] = (byte)messageBuffer.Length;
			rfm69Device.RegisterWrite(0x0, messageBuffer);

			// Transmit mode once FIFO loaded
			rfm69Device.RegisterWriteByte(0x01, 0b00001100);

			// Wait until send done, no timeouts in PoC
			Debug.WriteLine("Send-wait");
			byte IrqFlags = rfm69Device.RegisterReadByte(0x28); // RegIrqFlags2
			while ((IrqFlags & 0b00001000) == 0)  // wait until TxDone cleared
			{
				Task.Delay(10).Wait();
				IrqFlags = rfm69Device.RegisterReadByte(0x28); // RegIrqFlags
				Debug.Write(".");
			}
			Debug.WriteLine("");

			// Standby mode while sleeping
			rfm69Device.RegisterWriteByte(0x01, 0b00000100);
			Debug.WriteLine($"{DateTime.Now.ToLongTimeString()}Send-Done");
			Task.Delay(5000).Wait();
		}
	}
}

My Arduino device then started receiving messages from my Raspberry PI 3 running Windows 10 IoT Core.

20:03:57.288 -> 0x3C: 0x1
20:03:57.288 -> 0x3D: 0x0
20:03:57.322 -> Start RX...
20:03:58.648 -> MessageIn:hello world 8:03:58 PM
20:04:03.920 -> MessageIn:hello world 8:04:03 PM
20:04:09.161 -> MessageIn:hello world 8:04:09 PM
20:04:14.421 -> MessageIn:hello world 8:04:14 PM
20:04:19.662 -> MessageIn:hello world 8:04:19 PM
20:04:24.895 -> MessageIn:hello world 8:04:24 PM
20:04:30.139 -> MessageIn:hello world 8:04:30 PM
20:04:35.392 -> MessageIn:hello world 8:04:35 PM
20:04:40.637 -> MessageIn:hello world 8:04:40 PM
20:04:45.890 -> MessageIn:hello world 8:04:45 PM
20:04:51.158 -> MessageIn:hello world 8:04:51 PM

Transmit is working! Though it’s starting to look like I might have to create my own lightweight Arduino RFM69HCW library “inspired” by the Arduino-LoRa library.

RFM69 hat library Part4B

Transmit Basic: iwanders/plainRFM69

My first Arduino client was based on the plainRFM69 library which looks fairly lightweight (it has in memory message queues). I started by adapting the plainRFM69 “Minimal” sample.

/*
 *  Copyright (c) 2014, Ivor Wanders
 *  MIT License, see the LICENSE.md file in the root folder.
*/
#include <SPI.h>
#include <plainRFM69.h>

// slave select pin.
#define SLAVE_SELECT_PIN 10     

// connected to the reset pin of the RFM69.
#define RESET_PIN 9

// tie this pin down on the receiver.
#define SENDER_DETECT_PIN 4

/*
    This is very minimal, it does not use the interrupt.

    Using the interrupt is recommended.
*/

plainRFM69 rfm = plainRFM69(SLAVE_SELECT_PIN);

void sender(){

    uint32_t start_time = millis();

    uint32_t counter = 0; // the counter which we are going to send.

    while(true){
        rfm.poll(); // run poll as often as possible.

        if (!rfm.canSend()){
            continue; // sending is not possible, already sending.
        }
        if ((millis() - start_time) > 500){ // every 500 ms. 
            start_time = millis();

            // be a little bit verbose.
            Serial.print("Send:");Serial.println(counter);

//            rfm.dumpRegisters(Serial);

            // send the number of bytes equal to that set with setPacketLength.
            // read those bytes from memory where counter starts.
            rfm.send(&counter);
            
            counter++; // increase the counter.
        }
    }
}

void receiver(){
    uint32_t counter = 0; // to count the messages.

    while(true){

        rfm.poll(); // poll as often as possible.

        while(rfm.available()){ // for all available messages:

            uint32_t received_count = 0; // temporary for the new counter.
            uint8_t len = rfm.read(&received_count); // read the packet into the new_counter.

            // print verbose output.
            Serial.print("Packet ("); Serial.print(len); Serial.print("): "); Serial.println(received_count);

            if (counter+1 != received_count){
                // if the increment is larger than one, we lost one or more packets.
                Serial.println("Packetloss detected!");
            }

            // assign the received counter to our counter.
            counter = received_count;
        }
    }
}

void setup(){
    Serial.begin(9600);
    SPI.begin();

    bareRFM69::reset(RESET_PIN); // sent the RFM69 a hard-reset.

    rfm.setRecommended(); // set recommended paramters in RFM69.
    rfm.setPacketType(false, false); // set the used packet type.

    rfm.setBufferSize(2);   // set the internal buffer size.
    rfm.setPacketLength(4); // set the packet length.
    rfm.setFrequency((uint32_t) 915*1000*1000); // set the frequency.

    // baudrate is default, 4800 bps now.
    rfm.dumpRegisters(Serial);
    
    rfm.receive();
    // set it to receiving mode.

    pinMode(SENDER_DETECT_PIN, INPUT_PULLUP);
    delay(5);
}

void loop(){
    if (digitalRead(SENDER_DETECT_PIN) == LOW){
        Serial.println("Going Receiver!");
        receiver(); 
        // this function never returns and contains an infinite loop.
    } else {
        Serial.println("Going sender!");
        sender();
        // idem.
    }
}
Arduino RFM69HCW Client in receive mode

I added code to dump the all the Arduino Nano Radio Shield RFM69/95 registers so I could compare it with my Adafruit RFM69HCW Radio Bonnet configuration. I also modified the code to set the three frequency registers so they matched the sample values based on the calculation in the RFM69HCW datasheet. I spent a lot of time manually configuring individual registers on the Adafruit bonnet (ignoring registers like 0x24 RegRssiValue).

void bareRFM69::dumpRegisters(Stream& out)
{
  for (int i = 0; i <= 0x3d; i++) {
    out.print("0x");
    out.print(i, HEX);
    out.print(": 0x");
    out.println(this->readRegister(i), HEX);
  }
}

void plainRFM69::setFrequency(uint32_t freq){
     uint64_t frf = ((uint64_t)freq << 19) / 32000000;
    this->setFrf(frf);
}

After much “trial and error” I found that my Arduino device would only receive messages from my Windows 10 IoT Core device when a third Arduino device was transmitting.

21:10:50.819 -> 0x0: 0x0
21:10:50.819 -> 0x1: 0x4
21:10:50.852 -> 0x2: 0x0
21:10:50.852 -> 0x3: 0x1A
21:10:50.852 -> 0x4: 0xB
21:10:50.886 -> 0x5: 0x0
21:10:50.886 -> 0x6: 0x52
21:10:50.886 -> 0x7: 0xE4
21:10:50.920 -> 0x8: 0xC0
21:10:50.920 -> 0x9: 0x0
21:10:50.920 -> 0xA: 0x41
21:10:50.954 -> 0xB: 0x40
21:10:50.954 -> 0xC: 0x2
21:10:50.954 -> 0xD: 0x92
21:10:50.988 -> 0xE: 0xF5
21:10:50.988 -> 0xF: 0x20
21:10:50.988 -> 0x10: 0x24
21:10:51.022 -> 0x11: 0x9F
21:10:51.022 -> 0x12: 0x9
21:10:51.056 -> 0x13: 0x1A
21:10:51.056 -> 0x14: 0x40
21:10:51.056 -> 0x15: 0xB0
21:10:51.089 -> 0x16: 0x7B
21:10:51.089 -> 0x17: 0x9B
21:10:51.089 -> 0x18: 0x88
21:10:51.124 -> 0x19: 0x55
21:10:51.124 -> 0x1A: 0x8B
21:10:51.124 -> 0x1B: 0x40
21:10:51.157 -> 0x1C: 0x80
21:10:51.157 -> 0x1D: 0x6
21:10:51.157 -> 0x1E: 0x10
21:10:51.191 -> 0x1F: 0x0
21:10:51.191 -> 0x20: 0x0
21:10:51.191 -> 0x21: 0x0
21:10:51.226 -> 0x22: 0x0
21:10:51.226 -> 0x23: 0x2
21:10:51.226 -> 0x24: 0xFF
21:10:51.260 -> 0x25: 0x0
21:10:51.260 -> 0x26: 0x5
21:10:51.293 -> 0x27: 0x80
21:10:51.293 -> 0x28: 0x0
21:10:51.293 -> 0x29: 0xFF
21:10:51.328 -> 0x2A: 0x0
21:10:51.328 -> 0x2B: 0x0
21:10:51.328 -> 0x2C: 0x0
21:10:51.363 -> 0x2D: 0x3
21:10:51.363 -> 0x2E: 0x98
21:10:51.363 -> 0x2F: 0x1
21:10:51.363 -> 0x30: 0x1
21:10:51.397 -> 0x31: 0x1
21:10:51.397 -> 0x32: 0x1
21:10:51.397 -> 0x33: 0x0
21:10:51.432 -> 0x34: 0x0
21:10:51.432 -> 0x35: 0x0
21:10:51.466 -> 0x36: 0x0
21:10:51.466 -> 0x37: 0x50
21:10:51.466 -> 0x38: 0x4
21:10:51.500 -> 0x39: 0x0
21:10:51.500 -> 0x3A: 0x0
21:10:51.500 -> 0x3B: 0x0
21:10:51.535 -> 0x3C: 0x1
21:10:51.535 -> 0x3D: 0x0
21:10:51.535 -> Going Receiver!
21:10:51.672 -> Packet (4): 27
21:10:51.672 -> Packetloss detected!
21:10:52.151 -> Packet (4): 28
21:10:52.665 -> Packet (4): 29
21:10:53.182 -> Packet (4): 30
21:10:53.664 -> Packet (4): 31
21:10:54.665 -> Packet (4): 33
21:10:54.699 -> Packetloss detected!
21:10:55.178 -> Packet (4): 34
21:10:56.177 -> Packet (4): 36
21:10:56.177 -> Packetloss detected!
21:10:56.660 -> Packet (4): 37
21:10:57.180 -> Packet (4): 38
21:10:57.666 -> Packet (4): 39
21:10:58.151 -> Packet (4): 40
21:10:58.669 -> Packet (4): 41
21:10:59.186 -> Packet (4): 42
21:10:59.668 -> Packet (4): 43
21:11:00.191 -> Packet (4): 44
21:11:00.666 -> Packet (4): 45
21:11:01.182 -> Packet (4): 46
21:11:01.664 -> Packet (4): 47
21:11:02.183 -> Packet (4): 48
21:11:02.664 -> Packet (4): 49
21:11:03.182 -> Packet (4): 50
21:11:03.664 -> Packet (4): 51

I think the interoperability problem was caused by timing differences caused by the plainRFM69 library using AutoMode (see datasheet section 4.4) to sequence the transmit process rather than manually changing the mode etc.

AutoMode option looks promising and warrants further investigation but interoperability will be an issue.

void plainRFM69::sendPacket(void* buffer, uint8_t len){
    /*
        Just like with Receive mode, the automode is used.

        First, Rx mode is disabled by going into standby.
        Then the automode is set to start transmitting when FIFO level is above
        the thresshold, it stops transmitting after PacketSent is asserted.

        This results in a minimal Tx time and packetSent can be detected when
        automode is left again.
        
    */
    this->setMode(RFM69_MODE_SEQUENCER_ON | RFM69_MODE_STANDBY);
    this->setAutoMode(RFM69_AUTOMODE_ENTER_RISING_FIFOLEVEL, RFM69_AUTOMODE_EXIT_RISING_PACKETSENT, RFM69_AUTOMODE_INTERMEDIATEMODE_TRANSMITTER);
    // perhaps RFM69_AUTOMODE_ENTER_RISING_FIFONOTEMPTY is faster?
    
    // set it into automode for transmitting

    // p22 - Turn on the high power boost registers in transmitting mode.
    if (this->tx_power_boosted)
    {
        this->setPa13dBm1(true);
        this->setPa13dBm2(true);
    }

    // write the fifo.
    this->state = RFM69_PLAIN_STATE_SENDING; // set the state to sending.
    this->writeFIFO(buffer, len);
}

Looks like I need to investigate some of the other Arduino library options.

RFM69 hat library Part4A

Transmit Basic Client Selection

My first milestone was to get my Adafruit RFM69HCW Radio Bonnet 433/868/915MHz sending packets to a program running on an Arduino device.

On GitHub there were quite a few RFM69 libraries, many of which were “based on”/”inspired by” the library by Felix Rusu from lowerPowerLab. (I have a number of LowPwerLab devices and they are pretty robust and reliable)

https://github.com/LowPowerLab/RFM69
https://github.com/dltech/RFM69
https://github.com/UKHASnet/ukhasnet-rfm69
https://github.com/jdesbonnet/RFM69_LPC812_firmware
https://github.com/grilletjesus
https://github.com/SamClarke2012/RFM69-AVR
https://github.com/boti7/RFM69-driver
https://github.com/ahessling/RFM69-STM32
https://github.com/tanchgen/wl_light
https://github.com/floxo/rfm69
https://github.com/JohnOH/raspirf
https://github.com/jgromes/RadioLib
https://github.com/flok99/RFM69
https://github.com/noearchimede/RFM69
https://gitlab.com/sedgwickcharles/RFM69
https://github.com/j54n1n/rfm69
https://github.com/DeltaNova/RFM69W
https://github.com/shaunhey/rfm69-elster
https://github.com/ivan-kralik/rfm69
https://github.com/rasmatic
https://github.com/iwanders/plainRFM69
https://www.hoperf.com/data/upload/back/20181204/RFM69-LCD-Listen-mode-code.rar

I was looking for something like the Arduino-LoRa library by Sandeep Mistry which was a fairly lightweight wrapper for the HopeRF RFM9X family of devices. I was looking for a library that didn’t change many of the default settings, have any in memory buffering or an implementation which included retries or transmit power adjustments.

The first version of the code to send packets was based on the example in part3.

public sealed class StartupTask : IBackgroundTask
{
    private const int ChipSelectLine = 1;
    private const int ResetLine = 25;
    private Rfm69HcwDevice rfm69Device = new Rfm69HcwDevice(ChipSelectLine, ResetLine);

    const double RH_RF6M9HCW_FXOSC = 32000000.0;
    const double RH_RFM69HCW_FSTEP = RH_RF6M9HCW_FXOSC / 524288.0;

    const byte NetworkID = 100;
    const byte NodeAddressFrom = 0x03;
    const byte NodeAddressTo = 0x02;


    public void Run(IBackgroundTaskInstance taskInstance)
    {
        rfm69Device.RegisterDump();

        // regOpMode standby
        rfm69Device.RegisterWriteByte(0x01, 0b00000100);

        // BitRate MSB/LSB
        rfm69Device.RegisterWriteByte(0x03, 0x34);
        rfm69Device.RegisterWriteByte(0x04, 0x00);

        // Frequency deviation
        rfm69Device.RegisterWriteByte(0x05, 0x02);
        rfm69Device.RegisterWriteByte(0x06, 0x3d);

        // Calculate the frequency according to the datasheett
        byte[] bytes = BitConverter.GetBytes((uint)(915000000.0 / RH_RFM69HCW_FSTEP));
        Debug.WriteLine("Byte Hex 0x{0:x2} 0x{1:x2} 0x{2:x2} 0x{3:x2}", bytes[0], bytes[1], bytes[2], bytes[3]);
        rfm69Device.RegisterWriteByte(0x07, bytes[2]);
        rfm69Device.RegisterWriteByte(0x08, bytes[1]);
        rfm69Device.RegisterWriteByte(0x09, bytes[0]);

        rfm69Device.RegisterWriteByte(0x38, 0x04);

        rfm69Device.RegisterDump();

        while (true)
        {
            // Standby mode while loading message into FIFO
            rfm69Device.RegisterWriteByte(0x01, 0b00000100);
            byte[] messageBuffer = BitConverter.GetBytes((uint)0);
            rfm69Device.RegisterWrite(0x0, messageBuffer);

            // Transmit mode once FIFO loaded
            rfm69Device.RegisterWriteByte(0x01, 0b00001100);

            // Wait until send done, no timeouts in PoC
            Debug.WriteLine("Send-wait");
            byte IrqFlags = rfm69Device.RegisterReadByte(0x28); // RegIrqFlags2
            while ((IrqFlags & 0b00001000) == 0)  // wait until TxDone cleared
            {
                Task.Delay(10).Wait();
                IrqFlags = rfm69Device.RegisterReadByte(0x28); // RegIrqFlags
                Debug.Write(".");
            }
            Debug.WriteLine("");

            // Standby mode while sleeping
            rfm69Device.RegisterWriteByte(0x01, 0b00000100);
            Debug.WriteLine($"{DateTime.Now.ToShortTimeString()}Send-Done");

            Task.Delay(5000).Wait();
        }
    }
}

For testing my client device was an Easy Sensors Arduino Nano Radio Shield RFM69/95

EasySensors Arduino Nano Shield

I could see bytes getting put in the send buffer and the PacketSent bit flag in RegIrqFlags2 register was getting sent which was positive.

Easy Sensors Arduino Nano Radio Shield RFM69/95 Payload Addressing client

After not much project work for a while some new RFM9X devices arrived from EasySensors in Belarus.

This sample client built with an Arduino Nano clone and an Arduino Nano radio shield RFM69/95 or NRF24L01+.

I used the shield’s onboard SHA204A crypto and authentication chip, a Seeedstudio Temperature & Humidity sensor and uploaded the data to Azure IoT Central (Will also work with my AdaFruit.IO LoRa field gateway).

/*
  Copyright ® 2018 November devMobile Software, All Rights Reserved

  THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY
  KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
  IMPLIED WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A PARTICULAR
  PURPOSE.

  You can do what you want with this code, acknowledgment would be nice.

  http://www.devmobile.co.nz

*/
#include <stdlib.h>
#include <LoRa.h>
#include <sha204_library.h>
#include <TH02_dev.h>

//#define DEBUG
//#define DEBUG_TELEMETRY
//#define DEBUG_LORA

// LoRa field gateway configuration (these settings must match your field gateway)
const char FieldGatewayAddress[] = {"LoRaIoT1"};
const float FieldGatewayFrequency =  915000000.0;
const byte FieldGatewaySyncWord = 0x12 ;

// Payload configuration
const int ChipSelectPin = 10;
const int ResetPin = 9;

// LoRa radio payload configuration
const byte SensorIdValueSeperator = ' ' ;
const byte SensorReadingSeperator = ',' ;
const int LoopSleepDelaySeconds = 60 ;

// ATSHA204 secure authentication, validation with crypto and hashing (currently only using for unique serial number)
const byte Atsha204Port = A3;
atsha204Class sha204(Atsha204Port);
const byte DeviceSerialNumberLength = 9 ;
byte deviceSerialNumber[DeviceSerialNumberLength] = {""};

const byte PayloadSizeMaximum = 64 ;
byte payload[PayloadSizeMaximum];
byte payloadLength = 0 ;


void setup()
{
  Serial.begin(9600);

#if DEBUG
  while (!Serial);
#endif
 
  Serial.println("Setup called");

  Serial.print("Field gateway:");
  Serial.print( FieldGatewayAddress ) ;
  Serial.print(" Frequency:");
  Serial.print( FieldGatewayFrequency,0 ) ;
  Serial.print("MHz SyncWord:");
  Serial.print( FieldGatewaySyncWord ) ;
  Serial.println();
  
   // Retrieve the serial number then display it nicely
  if(sha204.getSerialNumber(deviceSerialNumber))
  {
    Serial.println("sha204.getSerialNumber failed");
    while (true); // Drop into endless loop requiring restart
  }

  Serial.print("SNo:");
  for (int i = 0; i < sizeof( deviceSerialNumber) ; i++)
  {
    // Add a leading zero
    if ( deviceSerialNumber[i] < 16)
    {
      Serial.print("0");
    }
    Serial.print(deviceSerialNumber[i], HEX);
    Serial.print(" ");
  }
  Serial.println();

  Serial.println("LoRa setup start");

  // override the default chip select and reset pins
  LoRa.setPins(ChipSelectPin, ResetPin);
  if (!LoRa.begin(FieldGatewayFrequency))
  {
    Serial.println("LoRa begin failed");
    while (true); // Drop into endless loop requiring restart
  }

  // Need to do this so field gateway pays attention to messsages from this device
  LoRa.enableCrc();
  LoRa.setSyncWord(FieldGatewaySyncWord);

#ifdef DEBUG_LORA
  LoRa.dumpRegisters(Serial);
#endif
  Serial.println("LoRa Setup done.");

  // Configure the Seeedstudio TH02 temperature & humidity sensor
  Serial.println("TH02 setup start");
  TH02.begin();
  delay(100);
  Serial.println("TH02 setup done");

  PayloadHeader(FieldGatewayAddress,strlen(FieldGatewayAddress), deviceSerialNumber, DeviceSerialNumberLength);

  Serial.println("Setup done");
  Serial.println();
}


void loop()
{
  float temperature ;
  float humidity ;

  Serial.println("Loop called");

  PayloadReset();

  // Read the temperature & humidity values then display nicely
  temperature = TH02.ReadTemperature();
  Serial.print("T:");
  Serial.print(temperature, 1) ;
  Serial.println("C ") ;

  PayloadAdd( "T", temperature, 1);

  humidity = TH02.ReadHumidity();
  Serial.print("H:" );
  Serial.print(humidity, 0) ;
  Serial.println("% ") ;

  PayloadAdd( "H", humidity, 0) ;

#ifdef DEBUG_TELEMETRY
  Serial.println();
  Serial.print("RFM9X/SX127X Payload length:");
  Serial.print(payloadLength);
  Serial.println(" bytes");
#endif

  LoRa.beginPacket();
  LoRa.write(payload, payloadLength);
  LoRa.endPacket();

  Serial.println("Loop done");
  Serial.println();
  delay(LoopSleepDelaySeconds * 1000l);
}


void PayloadHeader(byte *to, byte toAddressLength, byte *from, byte fromAddressLength)
{
  byte addressesLength = toAddressLength + fromAddressLength ;

  payloadLength = 0 ;

  // prepare the payload header with "To" Address length (top nibble) and "From" address length (bottom nibble)
  
  payload[payloadLength] = (toAddressLength << 4) | fromAddressLength ;
  payloadLength += 1;

  // Copy the "To" address into payload
  memcpy(&payload[payloadLength], to, toAddressLength);
  payloadLength += toAddressLength ;

  // Copy the "From" into payload
  memcpy(&payload[payloadLength], from, fromAddressLength);
  payloadLength += fromAddressLength ;
}


void PayloadAdd( char *sensorId, float value, byte decimalPlaces)
{
  byte sensorIdLength = strlen( sensorId ) ;

  memcpy( &payload[payloadLength], sensorId,  sensorIdLength) ;
  payloadLength += sensorIdLength ;
  payload[ payloadLength] = SensorIdValueSeperator;
  payloadLength += 1 ;
  payloadLength += strlen( dtostrf(value, -1, decimalPlaces, (char *)&payload[payloadLength]));
  payload[ payloadLength] = SensorReadingSeperator;
  payloadLength += 1 ;
  
#ifdef DEBUG_TELEMETRY
  Serial.print("PayloadAdd float-payloadLength:");
  Serial.print( payloadLength);
  Serial.println( );
#endif
}


void PayloadAdd( char *sensorId, int value )
{
  byte sensorIdLength = strlen(sensorId) ;

  memcpy(&payload[payloadLength], sensorId,  sensorIdLength) ;
  payloadLength += sensorIdLength ;
  payload[ payloadLength] = SensorIdValueSeperator;
  payloadLength += 1 ;
  payloadLength += strlen(itoa( value,(char *)&payload[payloadLength],10));
  payload[ payloadLength] = SensorReadingSeperator;
  payloadLength += 1 ;
  
#ifdef DEBUG_TELEMETRY
  Serial.print("PayloadAdd int-payloadLength:" );
  Serial.print(payloadLength);
  Serial.println( );
#endif
}


void PayloadAdd( char *sensorId, unsigned int value )
{
  byte sensorIdLength = strlen(sensorId) ;

  memcpy(&payload[payloadLength], sensorId,  sensorIdLength) ;
  payloadLength += sensorIdLength ;
  payload[ payloadLength] = SensorIdValueSeperator;
  payloadLength += 1 ;
  payloadLength += strlen(utoa( value,(char *)&payload[payloadLength],10));
  payload[ payloadLength] = SensorReadingSeperator;
  payloadLength += 1 ;

#ifdef DEBUG_TELEMETRY
  Serial.print("PayloadAdd uint-payloadLength:");
  Serial.print(payloadLength);
  Serial.println( );
#endif
}


void PayloadReset()
{
  byte fromAddressLength = payload[0] & 0xf ;
  byte toAddressLength = payload[0] >> 4 ;
  
  payloadLength = toAddressLength + fromAddressLength + 1;
}

Arduino monitor output

ArduinoNanoEasySensorsRF95ShieldArduinoLogging

Prototype hardware

ArduinoNanoEasySensorsRF95ShieldHardware

Bill of materials (prices as at November 2018)

  • Arduino Nano clone USD4.70
  • Easy Sensors Arduino Nano Radio Shield for RFM95 USD16
  • Seeedstudio Temperature and Humidity Sensor Pro USD11.50
  • Seeedstudio 4 pin Male Jumper to Grove 4 pin Conversion Cable USD2.90

Azure IoT Central temperature and humidity display.

ArduinoNanoEasySensorsRF95ShieldAzureIoTCentral

Easy Sensors Wireless field gateway Arduino Nano client

After not much development on my nrf24L01 AdaFruit.IO and Azure IOT Hub field gateways for a while some new nRF24L01 devices arrived in the post last week.

This sample client is an Arduino Nano clone with an Arduino Nano radio shield for NRF24L01+.

I use the shield’s onboard SHA204A crypto and authentication chip, and a Seeedstudio Temperature & Humidity sensor with the data uploaded to adafruit.io.

/*
  Copyright ® 2018 September devMobile Software, All Rights Reserved

  THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY
  KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
  IMPLIED WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A PARTICULAR
  PURPOSE.

  You can do what you want with this code, acknowledgment would be nice.

  http://www.devmobile.co.nz

*/
#include &lt;RF24.h&gt;
#include &lt;sha204_library.h&gt;
#include &lt;TH02_dev.h&gt;

// RF24 radio( ChipeEnable , ChipSelect )
RF24 radio(9, 10);
const byte FieldGatewayChannel = 15 ;
const byte FieldGatewayAddress[] = {"Base1"};
const rf24_datarate_e RadioDataRate = RF24_250KBPS;
const rf24_pa_dbm_e RadioPALevel = RF24_PA_HIGH;

// Payload configuration
const int PayloadSizeMaximum = 32 ;
char payload[PayloadSizeMaximum] = "";
const byte DeviceIdPlusCsvSensorReadings = 1 ;
const byte SensorReadingSeperator = ',' ;

// ATSHA204 secure authentication, validation with crypto and hashing (only using for unique serial number)
atsha204Class sha204(A3);
const int DeviceSerialNumberLength = 9 ;
uint8_t deviceSerialNumber[DeviceSerialNumberLength] = {""};
const int LoopSleepDelaySeconds = 10 ;

void setup()
{
  Serial.begin(9600);
  Serial.println("Setup called");

  // Retrieve the serial number then display it nicely
  sha204.getSerialNumber(deviceSerialNumber);

  Serial.print("SNo:");
  for (int i = 0; i &lt; sizeof( deviceSerialNumber) ; i++)
  {
    // Add a leading zero
    if ( deviceSerialNumber[i] &lt; 16)
    {
      Serial.print("0");
    }
    Serial.print(deviceSerialNumber[i], HEX);
    Serial.print(" ");
  }

  Serial.println();

  // Configure the Seeedstudio TH02 temperature &amp; humidity sensor
  Serial.println("TH02 setup");
  TH02.begin();
  delay(100);

  // Configure the nRF24 module
  Serial.println("nRF24 setup");
  radio.begin();
  radio.setChannel(FieldGatewayChannel);
  radio.openWritingPipe(FieldGatewayAddress);
  radio.setDataRate(RadioDataRate) ;
  radio.setPALevel(RadioPALevel);
  radio.enableDynamicPayloads();

  Serial.println("Setup done");
}

void loop()
{
  int payloadLength = 0 ;
  float temperature ;
  float humidity ;

  Serial.println("Loop called");
  memset( payload, 0, sizeof( payload));

  // prepare the payload header with PayloadMessageType (top nibble) and DeviceID length (bottom nibble)
  payload[0] = (DeviceIdPlusCsvSensorReadings &lt;&lt; 4) | sizeof(deviceSerialNumber) ;
  payloadLength += 1;

  // Copy the device serial number into the payload
  memcpy( &amp;payload[payloadLength], deviceSerialNumber, sizeof( deviceSerialNumber));
  payloadLength += sizeof( deviceSerialNumber) ;

  // Read the temperature, humidity &amp; battery voltage values then display nicely
  temperature = TH02.ReadTemperature();
  Serial.print("T:");
  Serial.print( temperature, 1 ) ;
  Serial.print( "C" ) ;

  humidity = TH02.ReadHumidity();
  Serial.print(" H:");
  Serial.print( humidity, 0 ) ;
  Serial.println( "%" ) ;

  // Copy the temperature into the payload
  payload[ payloadLength] = 't';
  payloadLength += 1 ;
  dtostrf(temperature, 6, 1, &amp;payload[payloadLength]);
  payloadLength += 6;

  payload[ payloadLength] = ',';
  payloadLength += 1 ;

  // Copy the humidity into the payload
  payload[ payloadLength] = 'h';
  payloadLength += 1 ;
  dtostrf(humidity, 4, 0, &amp;payload[payloadLength]);
  payloadLength += 4;

  // Powerup the nRF24 chipset then send the payload to base station
  Serial.print( "Payload length:");
  Serial.println( payloadLength );

  Serial.println( "nRF24 write" ) ;
  boolean result = radio.write(payload, payloadLength);
  if (result)
    Serial.println("Write Ok...");
  else
    Serial.println("Write failed.");

  Serial.println("Loop done");
  delay(LoopSleepDelaySeconds * 1000l);
}

Arduino monitor output

NanoArduinoNrf24

Prototype hardware

ArduinoNanonRF24

Bill of materials (prices as at Sep 2018)

  • Arduino Nano clone USD4.70
  • Easy Sensors Arduino Nano Radio Shield for nRF24L01 USD13
  • Seeedstudio Temperature and Humidity Sensor Pro USD11.50
  • Seeedstudio 4 pin Male Jumper to Grove 4 pin Conversion Cable USD2.90

Adafruit.IO temperature display when I moved the sensor outside.

NanoNrf24