quote:

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Originally posted by mozobata


I am having a play with a Raspberry Pi 3 running Windows IoT. I have wired up a DS18B20 sensor and I am able to communicate to it fine via a UWP app.

I now wanted to make this app into a BackgroundTask app. I am using this code for the OneWire coms

class WireSearchResult
{
public byte[] id = new byte;
public int lastForkPoint = 0;
}
public class OneWire
{
private SerialDevice serialPort = null;
DataWriter dataWriteObject = null;
DataReader dataReaderObject = null;

public async Task<string> GetFirstSerialPort()
{
try
{
string aqs = SerialDevice.GetDeviceSelector("UART0");
var dis = await DeviceInformation.FindAllAsync(aqs);
if (dis.Count > 0)
{
var deviceInfo = dis.First();
return deviceInfo.Id;
}
}
catch (Exception ex)
{
Debug.WriteLine("Unable to get serial device: " + ex.Message);
}

return null;
}

public void shutdown()
{
if (serialPort != null)
{
serialPort.Dispose();
serialPort = null;
}
}

async Task<bool> onewireReset(string deviceId)
{
try
{
if (serialPort != null)
serialPort.Dispose();

serialPort = await SerialDevice.FromIdAsync(deviceId);

// Configure serial settings
serialPort.WriteTimeout = TimeSpan.FromMilliseconds(1000);
serialPort.ReadTimeout = TimeSpan.FromMilliseconds(1000);
serialPort.BaudRate = 9600;
serialPort.Parity = SerialParity.None;
serialPort.StopBits = SerialStopBitCount.One;
serialPort.DataBits = 8;
serialPort.Handshake = SerialHandshake.None;

dataWriteObject = new DataWriter(serialPort.OutputStream);
dataWriteObject.WriteByte(0xF0);
await dataWriteObject.StoreAsync();

dataReaderObject = new DataReader(serialPort.InputStream);
await dataReaderObject.LoadAsync(1);
byte resp = dataReaderObject.ReadByte();
if (resp == 0xFF)
{
System.Diagnostics.Debug.WriteLine("Nothing connected to UART");
return false;
}
else if (resp == 0xF0)
{
System.Diagnostics.Debug.WriteLine("No 1-wire devices are present");
return false;
}
else
{
//System.Diagnostics.Debug.WriteLine("Response: " + resp);
serialPort.Dispose();
serialPort = await SerialDevice.FromIdAsync(deviceId);

// Configure serial settings
serialPort.WriteTimeout = TimeSpan.FromMilliseconds(1000);
serialPort.ReadTimeout = TimeSpan.FromMilliseconds(1000);
serialPort.BaudRate = 115200;
serialPort.Parity = SerialParity.None;
serialPort.StopBits = SerialStopBitCount.One;
serialPort.DataBits = 8;
serialPort.Handshake = SerialHandshake.None;
dataWriteObject = new DataWriter(serialPort.OutputStream);
dataReaderObject = new DataReader(serialPort.InputStream);
return true;
}
}
catch (Exception ex)
{
System.Diagnostics.Debug.WriteLine("Exception: " + ex.Message);
return false;
}
}

public async Task onewireWriteByte(byte b)
{
for (byte i = 0; i < 8; i++, b = (byte)(b >> 1))
{
// Run through the bits in the byte, extracting the
// LSB (bit 0) and sending it to the bus
await onewireBit((byte)(b & 0x01));
}
}

async Task<byte> onewireBit(byte b)
{
var bit = b > 0 ? 0xFF : 0x00;
dataWriteObject.WriteByte((byte)bit);
await dataWriteObject.StoreAsync();
await dataReaderObject.LoadAsync(1);
var data = dataReaderObject.ReadByte();
return (byte)(data & 0xFF);
}

async Task<byte> onewireReadByte()
{
byte b = 0;
for (byte i = 0; i < 8; i++)
{
// Build up byte bit by bit, LSB first
b = (byte)((b >> 1) + 0x80 * await onewireBit(1));
}
// System.Diagnostics.Debug.WriteLine("onewireReadByte result: " + b);
return b;
}

public async Task<double> getTemperature(string deviceId)
{
double tempCelsius = -200;

if (await onewireReset(deviceId))
{
await onewireWriteByte(0xCC); //1-Wire SKIP ROM command (ignore device id)
await onewireWriteByte(0x44); //DS18B20 convert T command
// (initiate single temperature conversion)
// thermal data is stored in 2-byte temperature
// register in scratchpad memory

// Wait for at least 750ms for data to be collated
await Task.Delay(750);

// Get the data
await onewireReset(deviceId);
await onewireWriteByte(0xCC); //1-Wire Skip ROM command (ignore device id)
await onewireWriteByte(0xBE); //DS18B20 read scratchpad command
// DS18B20 will transmit 9 bytes to master (us)
// starting with the LSB

byte tempLSB = await onewireReadByte(); //read lsb
byte tempMSB = await onewireReadByte(); //read msb

// Reset bus to stop sensor sending unwanted data
await onewireReset(deviceId);

// Log the Celsius temperature
tempCelsius = ((tempMSB * 256) + tempLSB) / 16.0;
var temp2 = ((tempMSB << 8) + tempLSB) * 0.0625; //just another way of calculating it

System.Diagnostics.Debug.WriteLine("Temperature: " + tempCelsius + " degrees C " + temp2);
}
return tempCelsius;
}
}

And finally the StartupTask

public sealed class StartupTask : IBackgroundTask
{
private BackgroundTaskDeferral deferral;

private OneWire onewire;
private string deviceId = string.Empty;
private bool inprog = false;
private Timer timer;

public void Run(IBackgroundTaskInstance taskInstance)
{
deferral = taskInstance.GetDeferral();

onewire = new OneWire();
deviceId = await onewire.GetFirstSerialPort();

if(deviceId != null)
await onewire.getTemperature(deviceId));

BackgroundTaskDeferral.Complete();
}

}

The problem I have is that when I run this code it hangs on one of the lines that disposes of the SerialDevice in OneWire class.

I have read in a few places that its related to the BackgroundTask and using Async/Await

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quote:

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Originally posted by anniel

I don't think you're in the right forum.

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