Added SHTC3 binding (#1067)

* Added SHTC3 binding

* Changes from the code review

* change .csproj

* Changes from the code review

* add use Ratio

* fix readme and use ReadUInt16BigEndian

* remove bad use of ReadUInt16BigEndian the temperature can be negative not humidity

* Update src/devices/Shtc3/Shtc3.cs
Co-authored-by: NKrzysztof Wicher <mordotymoja@gmail.com>

* Update src/devices/Shtc3/Shtc3.cs
Co-authored-by: NKrzysztof Wicher <mordotymoja@gmail.com>

* Update src/devices/Shtc3/Shtc3.cs
Co-authored-by: NKrzysztof Wicher <mordotymoja@gmail.com>

* Update src/devices/Shtc3/Shtc3.cs
Co-authored-by: NKrzysztof Wicher <mordotymoja@gmail.com>

* Update src/devices/Shtc3/Shtc3.cs
Co-authored-by: NKrzysztof Wicher <mordotymoja@gmail.com>

* update after review

* change status to internal
Co-authored-by: NKrzysztof Wicher <mordotymoja@gmail.com>

src/devices/Shtc3/README.md

+# SHTC3 - Temperature & Humidity Sensor
+
+SHTC3 is a digital humidity and temperature sensor designed especially for battery-driven high-volume consumer electronics application.
+To reduce power cosumption this project use capability of sensor to allow measurement in low power mode and active sleep mode.
+
+## Usage
+
+```C#
+I2cConnectionSettings settings = new I2cConnectionSettings(1, Iot.Device.Shtc3.Shtc3.DefaultI2cAddress);
+I2cDevice device = I2cDevice.Create(settings);
+
+using (Shtc3 sensor = new Shtc3(device))
+{
+    if (sensor.TryGetTemperatureAndHumidity(out var temperature, out var relativeHumidity))
+    {
+        // temperature (℃)
+        Console.WriteLine($"Temperature: {temperature.DegreesCelsius:0.#}\u00B0C");
+        // humidity (%)
+        Console.WriteLine($"Humidity: {relativeHumidity.Percent:0.#}%");
+    }
+
+    // Make sensor in sleep mode
+    sensor.Sleep();
+}
+```
+
+## References
+https://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/2_Humidity_Sensors/Datasheets/Sensirion_Humidity_Sensors_SHTC3_Datasheet.pdf

src/devices/Shtc3/Register.cs

+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace Iot.Device.Shtc3
+{
+    /// <summary>
+    /// Shtc3 Register
+    /// </summary>
+    internal enum Register : ushort
+    {
+        SHTC3_ID = 0xEFC8,
+        SHTC3_RESET = 0x805D,
+        SHTC3_SLEEP = 0xB098,
+        SHTC3_WAKEUP = 0x3517,
+
+        /// <summary>
+        /// Temperature and Humidity with Clock stretching disable in normal power mode
+        /// </summary>
+        SHTC3_MEAS_T_RH_POLLING_NPM = 0x7866,
+
+        /// <summary>
+        /// Temperature and Humidity with Clock Stretching enable and normal power mode
+        /// </summary>
+        SHTC3_MEAS_T_RH_CLOCKSTR_NPM = 0x7CA2,
+
+        /// <summary>
+        /// Temperature and Humidity with Clock stretching disable in low power mode
+        /// </summary>
+        SHTC3_MEAS_T_RH_POLLING_LPM = 0x609C,
+
+        /// <summary>
+        /// Temperature and Humidity with Clock stretching enable in low power mode
+        /// </summary>
+        SHTC3_MEAS_T_RH_CLOCKSTR_LPM = 0x6458,
+
+        /// <summary>
+        /// Humidity and Temperature with Clock stretching disable in normal power mode
+        /// </summary>
+        SHTC3_MEAS_RH_T_POLLING_NPM = 0x58E0,
+
+        /// <summary>
+        /// Humidity and Temperature with Clock stretching enable in normal power mode
+        /// </summary>
+        SHTC3_MEAS_RH_T_CLOCKSTR_NPM = 0x5C24,
+
+        /// <summary>
+        /// Humidity and Temperature with Clock stretching disable in low power mode
+        /// </summary>
+        SHTC3_MEAS_RH_T_POLLING_LPM = 0x401A,
+
+        /// <summary>
+        /// Humidity and Temperature with Clock stretching enable in low power mode
+        /// </summary>
+        SHTC3_MEAS_RH_T_CLOCKSTR_LPM = 0x44DE,
+    }
+}

src/devices/Shtc3/Shtc3.cs

+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Buffers.Binary;
+using System.Device;
+using System.Device.I2c;
+using System.Threading;
+using UnitsNet;
+
+namespace Iot.Device.Shtc3
+{
+    /// <summary>
+    /// Temperature and humidity sensor Shtc3
+    /// </summary>
+    public class Shtc3 : IDisposable
+    {
+        // CRC const
+        private const byte CRC_POLYNOMIAL = 0x31;
+        private const byte CRC_INIT = 0xFF;
+
+        /// <summary>
+        /// Default I2C address
+        /// </summary>
+        public const int DefaultI2cAddress = 0x70;
+
+        private I2cDevice _i2cDevice;
+        private int? _id = null;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Shtc3"/> class.
+        /// </summary>
+        /// <param name="i2cDevice">The I2C device used for communication.</param>
+        public Shtc3(I2cDevice i2cDevice)
+        {
+            if (i2cDevice == null)
+            {
+                throw new ArgumentNullException(nameof(i2cDevice));
+            }
+
+            _i2cDevice = i2cDevice;
+
+            Wakeup();
+            _status = Status.Idle;
+
+            Reset();
+        }
+
+        private Status _status;
+
+        /// <summary>
+        /// Set Shtc3 state
+        /// </summary>
+        public Status Status
+        {
+            get
+            {
+                return _status;
+            }
+        }
+
+        /// <summary>
+        /// Try read Temperature and Humidity
+        /// </summary>
+        /// <param name="temperature">Temperature returned by sensor</param>
+        /// <param name="relativeHumidity">Humidity return by sensor</param>
+        /// <param name="lowPower">"true" measured in low power mode, "false"(default) measured in normal power mode</param>
+        /// <param name="clockStretching">"true" allow clock stretching, "false" (default) without clock stretching</param>
+        /// <returns>True if operation was successful</returns>
+        public bool TryGetTemperatureAndHumidity(out Temperature temperature, out Ratio relativeHumidity, bool lowPower = false, bool clockStretching = false)
+        {
+            if (Status == Status.Sleep)
+            {
+                Wakeup();
+            }
+
+            Register cmd = GetMeasurementCmd(lowPower, clockStretching);
+
+            if (!TryReadSensorData(cmd, out var st, out var srh))
+            {
+                temperature = default(Temperature);
+                relativeHumidity = default(Ratio);
+                return false;
+            }
+
+            // Details in the Datasheet P9
+            temperature = Temperature.FromDegreesCelsius(Math.Round(st * 175 / 65536.0 - 45, 1));
+            relativeHumidity = Ratio.FromDecimalFractions(srh / 65536.0);
+            return true;
+        }
+
+        private bool TryReadSensorData(Register cmd, out double temperature, out double humidity)
+        {
+            Write(cmd);
+
+            Span<byte> readBuff = stackalloc byte[6];
+
+            _i2cDevice.Read(readBuff);
+
+            // Details in the Datasheet P7
+            int st = BinaryPrimitives.ReadInt16BigEndian(readBuff.Slice(0, 2));      // Temp
+            int srh = BinaryPrimitives.ReadUInt16BigEndian(readBuff.Slice(3, 2));     // Humi
+
+            // check 8-bit crc
+            bool tCrc = CheckCrc8(readBuff.Slice(0, 2), readBuff[2]);
+            bool rhCrc = CheckCrc8(readBuff.Slice(3, 2), readBuff[5]);
+            if (!tCrc || !rhCrc)
+            {
+                temperature = double.NaN;
+                humidity = double.NaN;
+                return false;
+            }
+
+            temperature = st;
+            humidity = srh;
+            return true;
+        }
+
+        private static Register GetMeasurementCmd(bool lowPower, bool clockStretching)
+        {
+            if (lowPower)
+            {
+                if (clockStretching)
+                {
+                    return Register.SHTC3_MEAS_T_RH_CLOCKSTR_LPM;
+                }
+                else
+                {
+                    return Register.SHTC3_MEAS_T_RH_POLLING_LPM;
+                }
+            }
+            else
+            {
+                if (clockStretching)
+                {
+                    return Register.SHTC3_MEAS_T_RH_CLOCKSTR_NPM;
+                }
+                else
+                {
+                    return Register.SHTC3_MEAS_T_RH_POLLING_NPM;
+                }
+            }
+        }
+
+        /// <summary>
+        /// SHTC3 Sleep
+        /// </summary>
+        public void Sleep()
+        {
+            if (Status == Status.Sleep)
+            {
+                return;
+            }
+
+            Write(Register.SHTC3_SLEEP);
+        }
+
+        /// <summary>
+        /// SHTC3 Wakeup
+        /// </summary>
+        private void Wakeup()
+        {
+            Write(Register.SHTC3_WAKEUP);
+        }
+
+        /// <summary>
+        /// SHTC3 Soft Reset
+        /// </summary>
+        public void Reset()
+        {
+            if (Status == Status.Sleep)
+            {
+                Wakeup();
+            }
+
+            Write(Register.SHTC3_RESET);
+        }
+
+        /// <summary>
+        /// Sensor Id
+        /// </summary>
+        public int? Id
+        {
+            get
+            {
+                return _id = _id ?? ReadId();
+            }
+        }
+
+        /// <summary>
+        /// Read Id
+        /// </summary>
+        private int? ReadId()
+        {
+            if (Status == Status.Sleep)
+            {
+                Wakeup();
+            }
+
+            Write(Register.SHTC3_ID);
+
+            Span<byte> readBuff = stackalloc byte[3];
+
+            _i2cDevice.Read(readBuff);
+
+            // check 8-bit crc
+            if (!CheckCrc8(readBuff.Slice(0, 2), readBuff[2]))
+            {
+                return null;
+            }
+
+            int id = BinaryPrimitives.ReadInt16BigEndian(readBuff.Slice(0, 2));
+
+            // check the result match to the SHTC3 product code
+            if (!ValidShtc3Id(id))
+            {
+                return null;
+            }
+
+            return id;
+        }
+
+        /// <summary>
+        /// Check the match to the SHTC3 product code
+        /// Table 15  while bits 11 and 5:0 contain the SHTC3 specific product code 0b_0000_1000_0000_0111
+        /// </summary>
+        /// <param name="id">Id to test</param>
+        /// <returns></returns>
+        private static bool ValidShtc3Id(int id)
+        {
+            return (id & 0b_0000_1000_0011_1111) == 0b_0000_1000_0000_0111;
+        }
+
+        /// <summary>
+        /// 8-bit CRC Checksum Calculation
+        /// </summary>
+        /// <param name="data">Raw Data</param>
+        /// <param name="crc8">Raw CRC8</param>
+        /// <returns>Checksum is true or false</returns>
+        private static bool CheckCrc8(ReadOnlySpan<byte> data, byte crc8)
+        {
+            // Details in the Datasheet table 16 P9
+            byte crc = CRC_INIT;
+            for (int i = 0; i < 2; i++)
+            {
+                crc ^= data[i];
+
+                for (int j = 8; j > 0; j--)
+                {
+                    if ((crc & 0x80) != 0)
+                    {
+                        crc = (byte)((crc << 1) ^ CRC_POLYNOMIAL);
+                    }
+                    else
+                    {
+                        crc = (byte)(crc << 1);
+                    }
+                }
+            }
+
+            return crc == crc8;
+        }
+
+        private void Write(Register register)
+        {
+            Span<byte> writeBuff = stackalloc byte[2];
+            BinaryPrimitives.WriteUInt16BigEndian(writeBuff, (ushort)register);
+
+            _i2cDevice.Write(writeBuff);
+
+            // wait SCL free
+            DelayHelper.DelayMilliseconds(20, false);
+        }
+
+        /// <summary>
+        /// Cleanup
+        /// </summary>
+        public void Dispose()
+        {
+            _i2cDevice?.Dispose();
+            _i2cDevice = null;
+        }
+    }
+}

src/devices/Shtc3/Shtc3.csproj

+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>netcoreapp3.1</TargetFramework>
+    <!--Disabling default items so samples source won't get build by the main library-->
+    <EnableDefaultItems>false</EnableDefaultItems>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="*.cs" />
+    <Compile Include="..\Common\System\Device\DelayHelper.cs" Link="DelayHelper.cs" />
+    <None Include="README.md" />
+    <ProjectReference Include="$(MainLibraryPath)System.Device.Gpio.csproj" />
+  </ItemGroup>
+
+</Project>

src/devices/Shtc3/Shtc3.sln

+
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+EndProject
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+EndGlobal

src/devices/Shtc3/Status.cs

+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace Iot.Device.Shtc3
+{
+    /// <summary>
+    /// Shtc3 Status
+    /// </summary>
+    internal enum Status
+    {
+        /// <summary>
+        /// Sensor ready to use
+        /// </summary>
+        Idle,
+
+        /// <summary>
+        /// Sensor in sleep mode
+        /// </summary>
+        Sleep
+    }
+}

src/devices/Shtc3/category.txt

+thermometer
+hygrometer

src/devices/Shtc3/samples/Program.cs

+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Device.I2c;
+using System.Threading;
+using Iot.Device.Common;
+using UnitsNet;
+
+namespace Iot.Device.Shtc3.Samples
+{
+    internal class Program
+    {
+        private static void Main(string[] args)
+        {
+            I2cConnectionSettings settings = new I2cConnectionSettings(1, Iot.Device.Shtc3.Shtc3.DefaultI2cAddress);
+            I2cDevice device = I2cDevice.Create(settings);
+
+            using (Shtc3 sensor = new Shtc3(device))
+            {
+                Console.WriteLine($"Sensor Id: {sensor.Id}");
+                while (true)
+                {
+                    // Try sensor measurement in normal power mode
+                    if (sensor.TryGetTemperatureAndHumidity(out var temperature, out var relativeHumidity))
+                    {
+                        Console.WriteLine($"====================In normal power mode===========================");
+                        ConsoleWriteInfo(temperature, relativeHumidity);
+                    }
+
+                    // Try sensor measurement in low power mode
+                    if (sensor.TryGetTemperatureAndHumidity(out temperature, out relativeHumidity, lowPower: true))
+                    {
+                        Console.WriteLine($"====================In low power mode===========================");
+                        ConsoleWriteInfo(temperature, relativeHumidity);
+                    }
+
+                    // Set sensor in sleep mode
+                    sensor.Sleep();
+
+                    Console.WriteLine();
+                    Thread.Sleep(1000);
+                }
+            }
+        }
+
+        private static void ConsoleWriteInfo(Temperature temperature, Ratio relativeHumidity)
+        {
+            Console.WriteLine($"Temperature: {temperature.DegreesCelsius:0.#}\u00B0C");
+            Console.WriteLine($"Humidity: {relativeHumidity.Percent:0.#}%");
+            // WeatherHelper supports more calculations, such as saturated vapor pressure, actual vapor pressure and absolute humidity.
+            Console.WriteLine($"Heat index: {WeatherHelper.CalculateHeatIndex(temperature, relativeHumidity).DegreesCelsius:0.#}\u00B0C");
+            Console.WriteLine($"Dew point: {WeatherHelper.CalculateDewPoint(temperature, relativeHumidity).DegreesCelsius:0.#}\u00B0C");
+        }
+
+    }
+}

src/devices/Shtc3/samples/README.md

+# SHTC3 - Samples
+
+## Hardware Required
+* SHTC3
+* Male/Female Jumper Wires
+
+## Circuit
+* SCL - SCL
+* SDA - SDA
+* VCC - 3.3V
+* GND - GND
+
+
+## Code
+```C#
+I2cConnectionSettings settings = new I2cConnectionSettings(1, Shtc3.DefaultI2cAddress);
+I2cDevice device = I2cDevice.Create(settings);
+
+using (Shtc3 sensor = new Shtc3(device))
+{
+    Console.WriteLine($"Sensor Id: {sensor.Id}");
+
+    while (true)
+    {
+            if (sensor.TryGetTemperatureAndHumidity(out var temperature, out var relativeHumidity))
+            {
+                Console.WriteLine($"Temperature: {temperature.DegreesCelsius:0.#}\u00B0C");
+                Console.WriteLine($"Relative humidity: {relativeHumidity.Percent:0.#}%");
+                // WeatherHelper supports more calculations, such as saturated vapor pressure, actual vapor pressure and absolute humidity.
+                Console.WriteLine($"Heat index: {WeatherHelper.CalculateHeatIndex(temperature, relativeHumidity).DegreesCelsius:0.#}\u00B0C");
+                Console.WriteLine($"Dew point: {WeatherHelper.CalculateDewPoint(temperature, relativeHumidity).DegreesCelsius:0.#}\u00B0C");
+                Console.WriteLine();
+            }
+
+        sensor.Sleep();
+
+        Thread.Sleep(1000);
+    }
+
+}
+
+```
+## Result
+![](RunningResult.JPG)

src/devices/Shtc3/samples/Shtc3.Samples.csproj

+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>netcoreapp3.1</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <None Remove="README.md" />
+    <None Remove="RunningResult.jpg" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\..\System.Device.Gpio\System.Device.Gpio.csproj" />
+    <ProjectReference Include="..\..\Common\CommonHelpers.csproj" />
+    <ProjectReference Include="..\Shtc3.csproj" />
+  </ItemGroup>
+
+</Project>