Register Read
Over the last couple of weeks I have been working on a Windows 10 IoT Core C# library for my Dragino LoRa GPS hat for Raspberry PI. I initially started with the Dragino.LoRa library but after some experimentation and hacking I decided to write my own library (which is usually not a good idea).
I wanted a lightweight LoRa only library (hopefully possible to backport to .NetMF) which didn’t try to hide how the Semtech 1276 chip functioned, and in the future could be configured to work with other vendors’ shields (dragino, electronictricks, elecrow, m2m).
I’m also working on an RFM69 Raspberry PI shield based on an electronictricks PCB populated with a RFM69HCW so I figured the experience of building a library would be useful.
The first step was to build a basic universal windows platform (UWP) background task to confirm that I could reliably communicate with the shield over SPI bus by reading a single register value (RegVersion the silicon version specified in the vendor datasheet).
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namespace devMobile.IoT.Rfm9x.RegisterRead
{
using System;
using System.Diagnostics;
using System.Threading.Tasks;
using Windows.ApplicationModel.Background;
using Windows.Devices.Gpio;
using Windows.Devices.Spi;
public sealed class StartupTask : IBackgroundTask
{
private const int ChipSelectLine = 25;
private SpiDevice rfm9XLoraModem;
public void Run(IBackgroundTaskInstance taskInstance)
{
// Have to setup the SPI bus with custom Chip Select line rather than std CE0/CE1
SpiController spiController = SpiController.GetDefaultAsync().AsTask().GetAwaiter().GetResult();
var settings = new SpiConnectionSettings(0)
{
ClockFrequency = 500000,
Mode = SpiMode.Mode0,
};
GpioController gpioController = GpioController.GetDefault();
GpioPin chipSelectGpioPin = gpioController.OpenPin(ChipSelectLine);
chipSelectGpioPin.SetDriveMode(GpioPinDriveMode.Output);
chipSelectGpioPin.Write(GpioPinValue.High);
rfm9XLoraModem = spiController.GetDevice(settings);
while (true)
{
byte[] writeBuffer = new byte[]{ 0x42 }; // RegVersion
byte[] readBuffer = new byte[1];
chipSelectGpioPin.Write(GpioPinValue.Low);
rfm9XLoraModem.Write(writeBuffer);
rfm9XLoraModem.Read(readBuffer);
chipSelectGpioPin.Write(GpioPinValue.High);
Debug.WriteLine("RegVersion {0:x2}", readBuffer[0]);
Task.Delay(10000).Wait();
}
}
}
}
The dragino shield has the chip select (also know as slave select) line connected to pin 25 rather than the usual CS0 (pin 24) & CS1 (pin 26) so it has to be manually strobed.
'backgroundTaskHost.exe' (CoreCLR: CoreCLR_UWP_Domain): Loaded 'C:\Data\Users\DefaultAccount\AppData\Local\DevelopmentFiles\RegisterRead-uwpVS.Debug_ARM.Bryn.Lewis\System.Diagnostics.Debug.dll'. Skipped loading symbols. Module is optimized and the debugger option 'Just My Code' is enabled. RegVersion 12 RegVersion 12
Next step was to dump all the registers of the HopeRF module.
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