public void Trigger()
{
changeReader.Clear();
var a = changeReader.WaitForItemsAsync(2); // two edges, measure the time between
a.Completed = GpioValueChanged;
// trigger an echo
driverPin.Write(GpioPinValue.High);
Wait(0.1); // datasheet says 10us would do but this too is fine
driverPin.Write(GpioPinValue.Low);
}
public async void getGPIODistance1()
{
if (_echoBackReader != null)
{
ManualResetEvent mre = new ManualResetEvent(false);
CancellationTokenSource source = new CancellationTokenSource();
source.CancelAfter(TimeSpan.FromMilliseconds(250));
_echoBackReader.Clear();
_echoBackReader.Start();
//Send pulse
_triggerPin.Write(GpioPinValue.High);
mre.WaitOne(TimeSpan.FromMilliseconds(0.01));
_triggerPin.Write(GpioPinValue.Low);
try
{
await _echoBackReader.WaitForItemsAsync(2).AsTask(source.Token);
IList <GpioChangeRecord> changeRecords = this._echoBackReader.GetAllItems();
//foreach (var i in changeRecords)
//{
// Debug.WriteLine(i.RelativeTime.ToString() + " " + (i.Edge == GpioPinEdge.FallingEdge ? "Falling" : "Rising"));
//}
TimeSpan d = changeRecords[1].RelativeTime.Subtract(changeRecords[0].RelativeTime);
GPIOTime = d.TotalSeconds;
GPIODistance = ROUNDTRIPSPEEDOFSOUND * GPIOTime;
}
catch (OperationCanceledException)
{
GPIOTime = -1;
GPIODistance = -1; //no measurement
}
_echoBackReader.Stop();
}
}
private async Task ReadValuesFromDhtAsync()
{
try
{
var reading = new DhtSensorReading();
CancellationTokenSource cancellationSource = new CancellationTokenSource();
cancellationSource.CancelAfter(TIMEOUT_DATA_READING);
_changeReader.Clear();
_changeReader.Start();
await SendInitialPulseAsync();
// Wait for 43 falling edges to show up
await _changeReader.WaitForItemsAsync(43).AsTask(cancellationSource.Token);
// discard first two falling edges
_changeReader.GetNextItem();
_changeReader.GetNextItem();
// pulse widths greater than 110us are considered 1's
TimeSpan oneThreshold = new TimeSpan(110 * 10000000 / 1000000);
TimeSpan current = _changeReader.GetNextItem().RelativeTime;
for (int i = 0; i < 40; i++)
{
TimeSpan next = _changeReader.GetNextItem().RelativeTime;
TimeSpan pulseWidth = next.Duration() - current.Duration();
if (pulseWidth.Duration() > oneThreshold.Duration())
{
reading.Bits[40 - i - 1] = true;
}
current = next;
}
if (reading.IsValid())
{
UpdateValuesOnUI(reading.Temperature(), reading.Humidity());
UpdateStatus("OK");
}
else
{
throw new Exception("Invalid sensor data received!");
}
}
catch (Exception ex)
{
UpdateValuesOnUI(double.NaN, double.NaN);
if (ex is TaskCanceledException)
{
UpdateStatus("Timeout while reading sensor data!");
}
else
{
UpdateStatus(ex.Message);
}
}
finally
{
_changeReader.Stop();
}
}