RFM69 shield library Part1

Register Read

After building an RFM95 Windows 10 IoT Core C# library I wanted to see if I could source a couple of RFM69HCW hats and write another library. For some applications the RFM69HCW with the variety and number of low-power client devices available plus, its built in payload encryption and addressing make it a better option. For the RFM9X library I purchased several RM9X Raspberry PI Hats but I can only find a couple (May 2019) of suitable RFM69HCW ones.

  • Adafruit RFM69HCW Radio Bonnet 433/868/915MHz USD19.95
  • Seegel Systeme RaspyRFMII EUR17.90

I wanted a lightweight RFM69HCW library which didn’t try to hide how the chip functioned, and in the future could be configured to work with other vendors’ shields.

AdaFruit LoRa 9X/RFM69HCW Radio Bonnet
Seegel Systeme RaspyRFM-II

The first step was to build a basic universal windows platform (UWP) background task to confirm that I could reliably communicate with the AdaFruit shield over the SPI bus by reading a single register value (RegVersion the silicon version specified in the vendor datasheet).

/*
    Copyright ® 2019 May 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

	 CS : CE1
	 RST : GPIO25
	 IRQ : GPIO22 (DIO0)
	 Unused : GPIO23 (DIO1)
	 Unused : GPIO24 (DIO2)
 */
namespace devMobile.IoT.Rfm69hcw.AdafruitSPI
{
	using System;
	using System.Diagnostics;
	using System.Threading;
	using Windows.ApplicationModel.Background;
	using Windows.Devices.Spi;

	public sealed class StartupTask : IBackgroundTask
	{
		private const byte RegVersion = 0x10;

		public void Run(IBackgroundTaskInstance taskInstance)
		{
			SpiController spiController = SpiController.GetDefaultAsync().AsTask().GetAwaiter().GetResult();
			var settings = new SpiConnectionSettings(1)
			{
				ClockFrequency = 500000,
				Mode = SpiMode.Mode0,
			};

			SpiDevice Device = spiController.GetDevice(settings);

			while (true)
			{
				byte[] writeBuffer = new byte[] { RegVersion }; // RegVersion
				byte[] readBuffer = new byte[1];

				Device.TransferSequential(writeBuffer, readBuffer);

				byte registerValue = readBuffer[0];
				Debug.WriteLine("Register 0x{0:x2} - Value 0X{1:x2} - Bits {2}", RegVersion, registerValue, Convert.ToString(registerValue, 2).PadLeft(8, '0'));

				Thread.Sleep(10000);
			}
		}
	}
}

The AdaFruit hat uses chip select 1

/*
    Copyright ® 2019 May 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

    The RaspyRFM is plugged into the Raspberry PI of pin 17-26.

    From the docs for the dual RFM69 mini 
    17 -> 3,3 V
    18 (GPIO 24) -> DIO1 bei Einzelmodul, DIO0 Slave bei Doppelmodul
    19 (MOSI) -> MOSI
    20 -> GND
    21 (MISO) ->MISO
    22 (GPIO 25) -> DIO0
    23 (SCK) -> SCK
    24 (CE0) -> NSS Master
    25 -> GND
    26 (CE1) -> DIO2 bei Einzelmodul, NSS Slave bei Doppelmodul
 */
namespace devMobile.IoT.Rfm69hcw.SeegelSpi
{
	using System;
	using System.Diagnostics;
	using System.Threading;
	using Windows.ApplicationModel.Background;
	using Windows.Devices.Spi;

	public sealed class StartupTask : IBackgroundTask
	{
		private const byte RegVersion = 0x10;

		public void Run(IBackgroundTaskInstance taskInstance)
		{
			SpiController spiController = SpiController.GetDefaultAsync().AsTask().GetAwaiter().GetResult();
			var settings = new SpiConnectionSettings(0)
			{
				ClockFrequency = 500000,
				Mode = SpiMode.Mode0,
			};

			SpiDevice Device = spiController.GetDevice(settings);

			while (true)
			{
				byte[] writeBuffer = new byte[] { RegVersion }; // RegVersion
				byte[] readBuffer = new byte[1];

				Device.TransferSequential(writeBuffer, readBuffer);

				byte registerValue = readBuffer[0];
				Debug.WriteLine("Register 0x{0:x2} - Value 0X{1:x2} - Bits {2}", RegVersion, registerValue, Convert.ToString(registerValue, 2).PadLeft(8, '0'));

				Thread.Sleep(10000);
			}
		}
	}
}

The Seegel hat uses chip select 0

Based on the datasheet the RegVersion (0x10) register the value (ox24) returned by both hats was correct.

'backgroundTaskHost.exe' (CoreCLR: CoreCLR_UWP_Domain): Loaded 'C:\Data\Programs\WindowsApps\Microsoft.NET.CoreFramework.Debug.2.2_2.2.27505.2_arm__8wekyb3d8bbwe\System.Threading.Thread.dll'. Skipped loading symbols. Module is optimized and the debugger option 'Just My Code' is enabled.
Register 0x10 - Value 0X24 - Bits 00100100
Register 0x10 - Value 0X24 - Bits 00100100
Register 0x10 - Value 0X24 - Bits 00100100

Next step is to dump all the registers of the HopeRF module