private void OnCharacteristicValueChanged(GattCharacteristic sender, GattValueChangedEventArgs args)
{
try
{
using (Stream s = args.CharacteristicValue.AsStream())
{
using (BinaryReader br = new BinaryReader(s))
{
LineSensorData lsd = CreateLineSensorData(br);
DeviceSentDataEvent?.Invoke(this, lsd);
}
}
}
catch (Exception e)
{
this.logger.Error(e, "unexpected exception while receiving data from BLE device");
}
}
private async Task <LineSensorReading> getLineSensorData(double currentPosition, int numberOfSamples, CancellationToken token)
{
bool callbackIsCalled = false;
Semaphore semaphore = new Semaphore(0, 1);
List <ushort[]> sensorValues = new List <ushort[]>();
DeviceSentDataEvent callback = (source, data) =>
{
callbackIsCalled = true;
if (token.IsCancellationRequested)
{
try
{
semaphore.Release();
}
catch (SemaphoreFullException)
{
// ignore as callback might get called multiple times after being cancelled
}
}
else if ((data.CurrentStatus & LineSensorStatus.LSS_OK_FLAG_NEW_DATA_AVAILABLE) == LineSensorStatus.LSS_OK_FLAG_NEW_DATA_AVAILABLE &&
(data.CurrentStatus & LineSensorStatus.LSS_ERROR) == 0)
{
lock (sensorValues)
{
if (sensorValues.Count >= numberOfSamples)
{
semaphore.Release();
}
else
{
sensorValues.Add(data.SensorValues);
}
}
}
};
this.wirelessLineSensor.DeviceSentDataEvent += callback;
try
{
// make sure we purge all old events before starting to receive new ones
while (callbackIsCalled)
{
callbackIsCalled = false;
await Task.Delay(500).ConfigureAwait(false);
}
bool success = false;
for (int i = 0; i < START_QUERYING_LINE_SENSOR_RETRIES_COUNT && !token.IsCancellationRequested; ++i)
{
if (await this.wirelessLineSensor.StartQueryingLineSensor().ConfigureAwait(false))
{
success = true;
break;
}
await Task.Delay(100).ConfigureAwait(false);
}
if (!success)
{
throw new InvalidOperationException("failed to start querying line sensor, wireless device might have disconnected or powered down");
}
#if DEBUG
if (!semaphore.WaitOne())
#else
if (!semaphore.WaitOne(TIMEOUT_TO_QUERY_LINE_SENSOR_MILLISECONDS))
#endif
{
throw new TimeoutException("querying line sensor timed out");
}
for (int i = 0; i < STOP_QUERYING_LINE_SENSOR_RETRIES_COUNT && !token.IsCancellationRequested; ++i)
{
if (await this.wirelessLineSensor.StopQueryingLineSensor().ConfigureAwait(false))
{
token.ThrowIfCancellationRequested();
if (sensorValues.Count < numberOfSamples)
{
throw new InvalidOperationException($"for some reason we collected {sensorValues.Count} sensor values which is less than {numberOfSamples} sensor values ");
}
else if (sensorValues.Count > numberOfSamples)
{
sensorValues = sensorValues.GetRange(0, numberOfSamples);
}
return(new LineSensorReading {
Position = currentPosition, SensorValues = sensorValues
});
}
await Task.Delay(100).ConfigureAwait(false);
}
throw new InvalidOperationException("failed to stop querying line sensor, wireless device might have disconnected or powered down");
}
finally
{
this.wirelessLineSensor.DeviceSentDataEvent -= callback;
}
}
