public Dht11Reading Read()
{
Dht11Reading reading = null;
int retryCount = 0;
bool failed;
do
{
failed = false;
try
{
reading = dht11.Sample();
reading.Failures = retryCount;
}
catch (TimeoutException tex)
{
statusText = $"Timed out waiting for sample. {tex.Message}";
failed = true;
}
catch (InvalidOperationException)
{
statusText = "Checksum validation failed";
failed = true;
}
catch
{
statusText = "Could not read data";
failed = true;
}
} while (failed && (++retryCount < 20));
if (!failed)
{
statusText = $"Succeeded ({retryCount} retries)";
}
System.Diagnostics.Debug.WriteLine(statusText);
return(reading);
}
public Dht11Reading Sample()
{
BitVector bits = new BitVector(40);
var oldLatency = System.Runtime.GCSettings.LatencyMode;
System.Runtime.GCSettings.LatencyMode = System.Runtime.GCLatencyMode.LowLatency;
try {
pin.SetDriveMode(GpioPinDriveMode.Output);
// Latch low value onto pin
pin.Write(GpioPinValue.Low);
// Wait for at least 18 ms
Task.Delay(sampleHoldLowMillis).Wait();
pin.Write(GpioPinValue.High);
Task.Delay(TimeSpan.FromTicks(200)).Wait();
var stopwatch = Stopwatch.StartNew();
// Set pin back to input
pin.SetDriveMode(inputDriveMode);
GpioPinValue previousValue = pin.Read();
// catch the first rising edge
for (;;)
{
if (stopwatch.ElapsedMilliseconds > initialRisingEdgeTimeoutMillis)
{
throw new TimeoutException("Initial Rising Timeout Exception");
}
GpioPinValue value = pin.Read();
if (value != previousValue)
{
// rising edge?
if (value == GpioPinValue.High)
{
break;
}
previousValue = value;
}
}
long prevTime = 0;
stopwatch.Restart();
// capture every falling edge until all bits are received or
// timeout occurs
for (uint i = 0; i < (bits.Length + 1);)
{
if (stopwatch.ElapsedMilliseconds > sampleTimeoutMillis)
{
throw new TimeoutException("Bits reading Timeout Exception");
}
GpioPinValue value = pin.Read();
if ((previousValue == GpioPinValue.High) && (value == GpioPinValue.Low))
{
// A falling edge was detected
// Calculate the microseconds in a fractional second
long now = (long)(stopwatch.Elapsed.TotalSeconds * 1000000);
if (i != 0)
{
var difference = now - prevTime;
bits[bits.Length - i] =
difference > oneThresholdMicroseconds;
}
prevTime = now;
++i;
}
previousValue = value;
}
var reading = new Dht11Reading(bits.ToULongValues()[0]);
if (!reading.IsValid)
{
// checksum mismatch
throw new InvalidOperationException("invalid checksum");
}
return(reading);
}
finally
{
System.Runtime.GCSettings.LatencyMode = oldLatency;
}
}
private async void refreshData(Dht11Reading data)
{
{
await textBlockTemp.Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal, () =>
{
if (data.IsValid)
{
this.textBlockTemp.Text = data.Temperature + "°C";
this.textBlockHum.Text = data.Humidity.ToString() + "%";
this.reading.Text = "";
if (data.Temperature >= 30)
{
rectangleTempDown.Fill = redBrush;
}
else
{
rectangleTempDown.Fill = orangeBrush;
}
if (data.Humidity >= 50)
{
rectangleHumDown.Fill = redBrush;
}
else
{
rectangleHumDown.Fill = orangeBrush;
}
rectangleTempUp.Height = 2 * (100 - data.Temperature);
rectangleTempDown.Height = 2 * data.Temperature;
rectangleHumUp.Height = 2 * (100 - data.Humidity);
rectangleHumDown.Height = 2 * data.Humidity;
}
});
}
}
public Dht11Reading Sample()
{
BitVector bits = new BitVector(40);
// Latch low value onto pin
pin.Write(GpioPinValue.Low);
// Set pin as output
pin.SetDriveMode(GpioPinDriveMode.Output);
// Wait for at least 18 ms
Task.Delay(sampleHoldLowMillis).Wait();
// Set pin back to input
pin.SetDriveMode(inputDriveMode);
GpioPinValue previousValue = pin.Read();
// catch the first rising edge
var stopwatch = Stopwatch.StartNew();
for (;;)
{
if (stopwatch.ElapsedMilliseconds > initialRisingEdgeTimeoutMillis)
{
throw new TimeoutException("Initial Rising Timeout Exception");
}
GpioPinValue value = pin.Read();
if (value != previousValue)
{
// rising edge?
if (value == GpioPinValue.High)
{
break;
}
previousValue = value;
}
}
long prevTime = 0;
stopwatch.Restart();
// capture every falling edge until all bits are received or
// timeout occurs
for (uint i = 0; i < (bits.Length + 1);)
{
if (stopwatch.ElapsedMilliseconds > sampleTimeoutMillis)
{
throw new TimeoutException("Bits reading Timeout Exception");
}
GpioPinValue value = pin.Read();
if ((previousValue == GpioPinValue.High) && (value == GpioPinValue.Low))
{
// A falling edge was detected
// Calculate the microseconds in a fractional second
long now = (long)(stopwatch.Elapsed.TotalSeconds * 1000000);
if (i != 0)
{
var difference = now - prevTime;
bits[bits.Length - i] =
difference > oneThresholdMicroseconds;
}
prevTime = now;
++i;
}
previousValue = value;
}
var reading = new Dht11Reading(bits.ToULongValues()[0]);
if (!reading.IsValid)
{
// checksum mismatch
throw new InvalidOperationException("invalid checksum");
}
return reading;
}
