Every so often my nanoFramework SX127X library RangeTester application wouldn’t start. When I poked around with the Visual Studio 2022 debugger the issue went away(a “Heisenbug” in the wild) which made figuring out what was going on impossible.
One afternoon the issue occurred several times in a row, the application wouldn’t startup because the SX127X device detection failed and message transmission was also not being confirmed.(TX Done).
public SX127XDevice(SpiDevice spiDevice, GpioController gpioController, int interruptPin, int resetPin)
{
_gpioController = gpioController;
// Factory reset pin configuration
_resetPin = resetPin;
_gpioController.OpenPin(resetPin, PinMode.Output);
_gpioController.Write(resetPin, PinValue.Low);
Thread.Sleep(20);
_gpioController.Write(resetPin, PinValue.High);
Thread.Sleep(100);
_registerManager = new RegisterManager(spiDevice, RegisterAddressReadMask, RegisterAddressWriteMask);
// Once the pins setup check that SX127X chip is present
Byte regVersionValue = _registerManager.ReadByte((byte)Configuration.Registers.RegVersion);
if (regVersionValue != Configuration.RegVersionValueExpected)
{
throw new ApplicationException("Semtech SX127X not found");
}
// Interrupt pin for RX message & TX done notification
_gpioController.OpenPin(interruptPin, PinMode.InputPullDown);
_gpioController.RegisterCallbackForPinValueChangedEvent(interruptPin, PinEventTypes.Rising, InterruptGpioPin_ValueChanged);
}
I could single step through the code and inspect variables with the debugger and it looks like a timing issue with order of the strobing of the reset pin and the initialisation of the RegisterManager. I’ll spend and hour starting and stopping the application, then smoke test the code for 24 hours with a couple of other devices generating traffic just to check.
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