Review remarks implemented

src/devices/Ahtxx/AhtBase.cs

@@ -22,7 +22,8 @@ namespace Iot.Device.Ahtxx
         /// </summary>
         public const int DeviceAddress = 0x38;
 
-        private enum StatusBit : byte // datasheet version 1.1, table 10
+        // datasheet version 1.1, table 10
+        private enum StatusBit : byte
         {
             Calibrated = 0x08,
             Busy = 0x80
@@ -35,7 +36,6 @@ namespace Iot.Device.Ahtxx
             Measure = 0xac
         }
 
-        private bool _disposed = false;
         private I2cDevice _i2cDevice = null;
         private double _temperature;
         private double _humidity;
@@ -48,7 +48,8 @@ namespace Iot.Device.Ahtxx
         {
             _i2cDevice = i2cDevice ?? throw new ArgumentNullException(nameof(i2cDevice));
 
-            SoftReset(); // even if not clearly stated in datasheet, start with a software reset to assure clear start conditions
+            // even if not clearly stated in datasheet, start with a software reset to assure clear start conditions
+            SoftReset();
 
             // check whether the device indicates the need for a calibration cycle
             // and perform calibration if indicated ==> c.f. datasheet, version 1.1, ch. 5.4
@@ -87,8 +88,9 @@ namespace Iot.Device.Ahtxx
         {
             Span<byte> buffer = stackalloc byte[3]
             {
+                // command parameters c.f. datasheet, version 1.1, ch. 5.4
                 (byte)Command.Measure,
-                0x33, // command parameters c.f. datasheet, version 1.1, ch. 5.4
+                0x33,
                 0x00
             };
             _i2cDevice.Write(buffer);
@@ -121,7 +123,8 @@ namespace Iot.Device.Ahtxx
         private void SoftReset()
         {
             _i2cDevice.WriteByte((byte)Command.SoftRest);
-            Thread.Sleep(20); // reset requires 20ms at most, c.f. datasheet version 1.1, ch. 5.5
+            // reset requires 20ms at most, c.f. datasheet version 1.1, ch. 5.5
+            Thread.Sleep(20);
         }
 
         /// <summary>
@@ -136,13 +139,15 @@ namespace Iot.Device.Ahtxx
                 0x00
             };
             _i2cDevice.Write(buffer);
-            Thread.Sleep(10); // wait 10ms c.f. datasheet, version 1.1, ch. 5.4
+            // wait 10ms c.f. datasheet, version 1.1, ch. 5.4
+            Thread.Sleep(10);
         }
 
         private byte GetStatusByte()
         {
             _i2cDevice.WriteByte(0x71);
-            Thread.Sleep(10); // whithout this delay the reading the status fails often.
+            // whithout this delay the reading the status fails often.
+            Thread.Sleep(10);
             byte status = _i2cDevice.ReadByte();
             return status;
         }
@@ -163,21 +168,13 @@ namespace Iot.Device.Ahtxx
         /// <inheritdoc cref="IDisposable" />
         protected virtual void Dispose(bool disposing)
         {
-            if (_disposed)
+            if (_i2cDevice == null)
             {
                 return;
             }
 
-            if (disposing)
-            {
-                if (_i2cDevice != null)
-                {
-                    _i2cDevice?.Dispose();
-                    _i2cDevice = null;
-                }
-            }
-
-            _disposed = true;
+            _i2cDevice?.Dispose();
+            _i2cDevice = null;
         }
     }
 }

src/devices/Ahtxx/category.txt

+hygrometers
+thermometers
\ No newline at end of file

src/devices/Ahtxx/samples/Ahtxx.Samples.csproj

@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>netcoreapp3.1</TargetFramework>
+    <TargetFramework>netcoreapp2.1</TargetFramework>
   </PropertyGroup>
 
   <ItemGroup>

src/devices/Mhz19b/Mhz19b.cs

@@ -38,7 +38,6 @@ namespace Iot.Device.Mhz19b
 
         private const int MessageSize = 9;
 
-        private bool _disposed = false;
         private SerialPort _serialPort = null;
 
         /// <summary>
@@ -47,9 +46,9 @@ namespace Iot.Device.Mhz19b
         /// <param name="uartDevice">Path to the UART device / serial port, e.g. /dev/serial0</param>
         public Mhz19b(string uartDevice)
         {
-            if (uartDevice == null)
+            if (string.IsNullOrEmpty(uartDevice))
             {
-                throw new ArgumentNullException(nameof(uartDevice));
+                throw new ArgumentException(nameof(uartDevice));
             }
 
             // create serial port using the setting acc. to datasheet, pg. 7, sec. general settings
@@ -66,7 +65,7 @@ namespace Iot.Device.Mhz19b
         /// If the validity is false the ratio is set to 0.
         /// </summary>
         /// <returns>CO2 concentration in ppm and validity</returns>
-        public (Ratio concentration, bool validity) GetCo2Reading()
+        public (VolumeConcentration concentration, bool validity) GetCo2Reading()
         {
             try
             {
@@ -86,23 +85,23 @@ namespace Iot.Device.Mhz19b
 
                 if (timeout == 0)
                 {
-                    return (Ratio.FromPartsPerMillion(0), false);
+                    return (VolumeConcentration.Zero, false);
                 }
 
                 // read and process response
                 byte[] response = new byte[MessageSize];
                 if ((_serialPort.Read(response, 0, response.Length) == response.Length) && (response[(int)MessageFormat.Checksum] == Checksum(response)))
                 {
-                    return (Ratio.FromPartsPerMillion((int)response[(int)MessageFormat.DataHighResponse] * 256 + (int)response[(int)MessageFormat.DataLowResponse]), true);
+                    return (VolumeConcentration.FromPartsPerMillion((int)response[(int)MessageFormat.DataHighResponse] * 256 + (int)response[(int)MessageFormat.DataLowResponse]), true);
                 }
                 else
                 {
-                    return (Ratio.FromPartsPerMillion(0), false);
+                    return (VolumeConcentration.Zero, false);
                 }
             }
             catch
             { // no need for details here
-                return (Ratio.FromPartsPerMillion(0), false);
+                return (VolumeConcentration.Zero, false);
             }
             finally
             {
@@ -115,20 +114,26 @@ namespace Iot.Device.Mhz19b
         /// The sensor doesn't respond anything, so this is fire and forget.
         /// </summary>
         /// <returns>true, if the command could be send</returns>
-        public bool ZeroPointCalibration() => SendRequest(CreateRequest(Command.CalibrateZeroPoint));
+        public bool PerformZeroPointCalibration() => SendRequest(CreateRequest(Command.CalibrateZeroPoint));
 
         /// <summary>
         /// Initiate a span point calibration.
         /// The sensor doesn't respond anything, so this is fire and forget.
         /// </summary>
-        /// <param name="span">span value, e.g. 2000[ppm]</param>
+        /// <param name="span">span value, between 1000[ppm] and 5000[ppm]. The typical value is 2000[ppm].</param>
         /// <returns>true, if the command could be send</returns>///
-        public bool SpanPointCalibration(int span)
+        /// <exception cref="System.Exception">Thrown when span value is out of range</exception>
+        public bool PerformSpanPointCalibration(VolumeConcentration span)
         {
+            if ((span.PartsPerMillion < 1000) || (span.PartsPerMillion > 5000))
+            {
+                throw new ArgumentException("Span value out of range (1000-5000[ppm])", nameof(span));
+            }
+
             var request = CreateRequest(Command.CalibrateSpanPoint);
             // set span in request, c. f. datasheet rev. 1.0, pg. 8 for details
-            request[(int)MessageFormat.DataHighRequest] = (byte)(span / 256);
-            request[(int)MessageFormat.DataLowRequest] = (byte)(span % 256);
+            request[(int)MessageFormat.DataHighRequest] = (byte)(span.PartsPerMillion / 256);
+            request[(int)MessageFormat.DataLowRequest] = (byte)(span.PartsPerMillion % 256);
 
             return SendRequest(request);
         }
@@ -139,7 +144,7 @@ namespace Iot.Device.Mhz19b
         /// </summary>
         /// <param name="state">State of automatic correction</param>
         /// <returns>true, if the command could be send</returns>
-        public bool AutomaticBaselineCorrection(AbmState state)
+        public bool SetAutomaticBaselineCorrection(AbmState state)
         {
             var request = CreateRequest(Command.AutoCalibrationSwitch);
             // set on/off state in request, c. f. datasheet rev. 1.0, pg. 8 for details
@@ -154,7 +159,7 @@ namespace Iot.Device.Mhz19b
         /// </summary>
         /// <param name="detectionRange">Detection range of the sensor</param>
         /// <returns>true, if the command could be send</returns>
-        public bool SensorDetectionRange(DetectionRange detectionRange)
+        public bool SetSensorDetectionRange(DetectionRange detectionRange)
         {
             var request = CreateRequest(Command.DetectionRangeSetting);
             // set detection range in request, c. f. datasheet rev. 1.0, pg. 8 for details
@@ -171,11 +176,13 @@ namespace Iot.Device.Mhz19b
             try
             {
                 _serialPort.Open();
-                _serialPort.Write(request, 0, request.Length);
-                return true;
+                // _serialPort.Write(request, 0, request.Length);
+                return false;
+                // return true;
             }
             catch
-            { // no need fo details here
+            {
+                // no need fo details here
                 return false;
             }
             finally
@@ -214,17 +221,13 @@ namespace Iot.Device.Mhz19b
         /// <inheritdoc cref="IDisposable" />
         public void Dispose()
         {
-            if (_disposed)
+            if (_serialPort == null)
             {
                 return;
             }
 
-            if (_serialPort != null)
-            {
-                _serialPort.Dispose();
-                _serialPort = null;
-                _disposed = true;
-            }
+            _serialPort.Dispose();
+            _serialPort = null;
         }
     }
 }
\ No newline at end of file

src/devices/Mhz19b/Mhz19b.csproj

@@ -9,7 +9,7 @@
   <ItemGroup>
     <Compile Include="*.cs" />
     <None Include="README.md" />
-    <PackageReference Include="System.IO.Ports" Version="5.0.0-rc.1.20451.14" />
+    <PackageReference Include="System.IO.Ports" Version="4.7.0" />
     <ProjectReference Include="$(MainLibraryPath)System.Device.Gpio.csproj" />
   </ItemGroup>
 

src/devices/Mhz19b/samples/Mhz19b.Sample.cs

@@ -19,16 +19,35 @@ namespace Iot.Device.Mhz19b.Samples
         public static void Main(string[] args)
         {
             Mhz19b sensor = new Mhz19b("/dev/serial0");
+
+            // Switch ABM on (default).
+            // sensor.SetAutomaticBaselineCorrection(AbmState.On);
+
+            // Set sensor detection range to 2000ppm (default).
+            // sensor.SetSensorDetectionRange(DetectionRange.Range2000);
+
+            // Perform calibration
+            // Step #1: perform zero point calibration
+            // Step #2: perform span point calibration at 2000ppm
+            // CAUTION: enable the following lines only if you know exactly what you do.
+            //          Consider also that zero point and span point calibration are performed
+            //          at different concentrations. The sensor requires up to 20 min to be
+            //          saturated at the target level.
+            // sensor.PerformZeroPointCalibration();
+            // ---- Now change to target concentration for span point.
+            // sensor.PerformSpanPointCalibration(VolumeConcentration.FromPartsPerMillion(200));
+
+            // Continously read current concentration
             while (true)
             {
-                (Ratio concentration, bool validity) reading = sensor.GetCo2Reading();
+                (VolumeConcentration concentration, bool validity) reading = sensor.GetCo2Reading();
                 if (reading.validity)
                 {
                     Console.WriteLine($"{reading.concentration}");
                 }
                 else
                 {
-                    Console.WriteLine("Concentration counldn't be read");
+                    Console.WriteLine("Concentration couldn't be read");
                 }
 
                 Thread.Sleep(1000);

src/devices/Mhz19b/samples/category.txt

+gas sensors
\ No newline at end of file