Transmit and Receive with Interrupts

For the final iteration of the “nasty” test harness I got the interrupts working for the transmitting and receiving of messages. It’s not quite simultaneous, the code sends a message every 10 seconds then goes back to receive continuous mode after each message has been sent.

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// Copyright (c) August 2018, devMobile Software
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namespace devMobile.IoT.Rfm9x.ReceiveTransmitInterrupt
{
	using System;
	using System.Diagnostics;
	using System.Text;
	using System.Runtime.InteropServices.WindowsRuntime;
	using System.Threading.Tasks;
	using Windows.ApplicationModel.Background;
	using Windows.Devices.Spi;
	using Windows.Devices.Gpio;

	public sealed class Rfm9XDevice
	{
		private SpiDevice Rfm9XLoraModem = null;
		private GpioPin ChipSelectGpioPin = null;
		private GpioPin InterruptGpioPin = null;
		private const byte RegisterAddressReadMask = 0X7f;
		private const byte RegisterAddressWriteMask = 0x80;

		public Rfm9XDevice(byte chipSelectPin, byte resetPin, byte interruptPin)
		{
			SpiController spiController = SpiController.GetDefaultAsync().AsTask().GetAwaiter().GetResult();
			var settings = new SpiConnectionSettings(0)
			{
				ClockFrequency = 500000,
				Mode = SpiMode.Mode0,
			};

			// Chip select pin configuration
			GpioController gpioController = GpioController.GetDefault();
			ChipSelectGpioPin = gpioController.OpenPin(chipSelectPin);
			ChipSelectGpioPin.SetDriveMode(GpioPinDriveMode.Output);
			ChipSelectGpioPin.Write(GpioPinValue.High);

			// Reset pin configuration to do factory reset
			GpioPin resetGpioPin = gpioController.OpenPin(resetPin);
			resetGpioPin.SetDriveMode(GpioPinDriveMode.Output);
			resetGpioPin.Write(GpioPinValue.Low);
			Task.Delay(10);
			resetGpioPin.Write(GpioPinValue.High);
			Task.Delay(10);

			// Interrupt pin for RX message & TX done notification
			InterruptGpioPin = gpioController.OpenPin(interruptPin);
			resetGpioPin.SetDriveMode(GpioPinDriveMode.Input);

			InterruptGpioPin.ValueChanged += InterruptGpioPin_ValueChanged;

			Rfm9XLoraModem = spiController.GetDevice(settings);
		}

		private void InterruptGpioPin_ValueChanged(GpioPin sender, GpioPinValueChangedEventArgs args)
		{
			if (args.Edge != GpioPinEdge.RisingEdge)
			{
				return;
			}

			byte IrqFlags = this.RegisterReadByte(0x12); // RegIrqFlags
			Debug.WriteLine(string.Format("RegIrqFlags {0}", Convert.ToString(IrqFlags, 2).PadLeft(8, '0')));
			if ((IrqFlags & 0b01000000) == 0b01000000)  // RxDone
			{
				Debug.WriteLine("Receive-Message");
				byte currentFifoAddress = this.RegisterReadByte(0x10); // RegFifiRxCurrent
				this.RegisterWriteByte(0x0d, currentFifoAddress); // RegFifoAddrPtr

				byte numberOfBytes = this.RegisterReadByte(0x13); // RegRxNbBytes

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

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

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

			if ((IrqFlags & 0b00001000) == 0b00001000)  // TxDone
			{
				this.RegisterWriteByte(0x01, 0b10000101); // RegOpMode set LoRa & RxContinuous
				Debug.WriteLine("Transmit-Done");
			}

			this.RegisterWriteByte(0x40, 0b00000000); // RegDioMapping1 0b00000000 DI0 RxReady & TxReady
			this.RegisterWriteByte(0x12, 0xff);// RegIrqFlags
		}

		public Byte RegisterReadByte(byte address)
		{
			byte[] writeBuffer = new byte[] { address &= RegisterAddressReadMask };
			byte[] readBuffer = new byte[1];
			Debug.Assert(Rfm9XLoraModem != null);

			ChipSelectGpioPin.Write(GpioPinValue.Low);
			Rfm9XLoraModem.Write(writeBuffer);
			Rfm9XLoraModem.Read(readBuffer);
			ChipSelectGpioPin.Write(GpioPinValue.High);

			return readBuffer[0];
		}

		public ushort RegisterReadWord(byte address)
		{
			byte[] writeBuffer = new byte[] { address &= RegisterAddressReadMask };
			byte[] readBuffer = new byte[2];
			Debug.Assert(Rfm9XLoraModem != null);

			ChipSelectGpioPin.Write(GpioPinValue.Low);
			Rfm9XLoraModem.Write(writeBuffer);
			Rfm9XLoraModem.Read(readBuffer);
			ChipSelectGpioPin.Write(GpioPinValue.High);

			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(Rfm9XLoraModem != null);

			ChipSelectGpioPin.Write(GpioPinValue.Low);
			Rfm9XLoraModem.Write(writeBuffer);
			Rfm9XLoraModem.Read(readBuffer);
			ChipSelectGpioPin.Write(GpioPinValue.High);

			return readBuffer;
		}

		public void RegisterWriteByte(byte address, byte value)
		{
			byte[] writeBuffer = new byte[] { address |= RegisterAddressWriteMask, value };
			Debug.Assert(Rfm9XLoraModem != null);

			ChipSelectGpioPin.Write(GpioPinValue.Low);
			Rfm9XLoraModem.Write(writeBuffer);
			ChipSelectGpioPin.Write(GpioPinValue.High);
		}

		public void RegisterWriteWord(byte address, ushort value)
		{
			byte[] valueBytes = BitConverter.GetBytes(value);
			byte[] writeBuffer = new byte[] { address |= RegisterAddressWriteMask, valueBytes[0], valueBytes[1] };
			Debug.Assert(Rfm9XLoraModem != null);

			ChipSelectGpioPin.Write(GpioPinValue.Low);
			Rfm9XLoraModem.Write(writeBuffer);
			ChipSelectGpioPin.Write(GpioPinValue.High);
		}

		public void RegisterWrite(byte address, [ReadOnlyArray()] byte[] bytes)
		{
			byte[] writeBuffer = new byte[1 + bytes.Length];
			Debug.Assert(Rfm9XLoraModem != null);

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

			ChipSelectGpioPin.Write(GpioPinValue.Low);
			Rfm9XLoraModem.Write(writeBuffer);
			ChipSelectGpioPin.Write(GpioPinValue.High);
		}

		public void RegisterDump()
		{
			Debug.WriteLine("Register dump");
			for (byte registerIndex = 0; registerIndex <= 0x42; 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 byte ChipSelectLine = 25;
		private const byte ResetLine = 17;
		private const byte InterruptLine = 4;
		private Rfm9XDevice rfm9XDevice = new Rfm9XDevice(ChipSelectLine, ResetLine, InterruptLine);
		private byte NessageCount = Byte.MaxValue;

		public void Run(IBackgroundTaskInstance taskInstance)
		{
			// Put device into LoRa + Sleep mode
			rfm9XDevice.RegisterWriteByte(0x01, 0b10000000); // RegOpMode 

			// Set the frequency to 915MHz
			byte[] frequencyWriteBytes = { 0xE4, 0xC0, 0x00 }; // RegFrMsb, RegFrMid, RegFrLsb
			rfm9XDevice.RegisterWrite(0x06, frequencyWriteBytes);

			rfm9XDevice.RegisterWriteByte(0x0F, 0x0); // RegFifoRxBaseAddress 

			// More power PA Boost
			rfm9XDevice.RegisterWriteByte(0x09, 0b10000000); // RegPaConfig

			rfm9XDevice.RegisterWriteByte(0x01, 0b10000101); // RegOpMode set LoRa & RxContinuous

			while (true)
			{
				rfm9XDevice.RegisterWriteByte(0x0E, 0x0); // RegFifoTxBaseAddress 

				// Set the Register Fifo address pointer
				rfm9XDevice.RegisterWriteByte(0x0D, 0x0); // RegFifoAddrPtr 

				string messageText = "W10 IoT Core LoRa! " + NessageCount.ToString();
				NessageCount -= 1;

				// load the message into the fifo
				byte[] messageBytes = UTF8Encoding.UTF8.GetBytes(messageText);
				foreach (byte b in messageBytes)
				{
					rfm9XDevice.RegisterWriteByte(0x0, b); // RegFifo
				}

				// Set the length of the message in the fifo
				rfm9XDevice.RegisterWriteByte(0x22, (byte)messageBytes.Length); // RegPayloadLength
				rfm9XDevice.RegisterWriteByte(0x40, 0b01000000); // RegDioMapping1 0b00000000 DI0 RxReady & TxReady
				rfm9XDevice.RegisterWriteByte(0x01, 0b10000011); // RegOpMode 

				Debug.WriteLine("Sending {0} bytes message {1}", messageBytes.Length, messageText);

				Task.Delay(10000).Wait();
			}
		}
	}
}

The diagnostic output shows inbound and outbound messages

RegIrqFlags 01010000
Receive-Message
Received 16 byte message HeLoRa World! 80
Sending 22 bytes message W10 IoT Core LoRa! 255
RegIrqFlags 01011000
Receive-Message
Received 16 byte message HeLoRa World! 80
Transmit-Done
RegIrqFlags 01010000
Receive-Message
Received 16 byte message HeLoRa World! 82
RegIrqFlags 01010000
Receive-Message
Received 16 byte message HeLoRa World! 84
The thread 0xf20 has exited with code 0 (0x0).
The thread 0xbe4 has exited with code 0 (0x0).
RegIrqFlags 01010000
Receive-Message
Received 16 byte message HeLoRa World! 86
RegIrqFlags 01010000
Receive-Message
Received 16 byte message HeLoRa World! 88
Sending 22 bytes message W10 IoT Core LoRa! 254
RegIrqFlags 00001000
Transmit-Done
RegIrqFlags 01110000
Receive-Message
Received 46 byte message ��Lh��ORegIrqFlags 01010000
Receive-Message
Received 16 byte message HeLoRa World! 92
The RegIrqFlags 01011000 indicates the RxDone, ValidHeader, and TxDone flags were set which was what I was expecting. Note the interference, the 46 byte packet

Next step is some refactoring to extract the register access code and figuring out a reasonable approach for RMF9X library.