Refactoring RTC Devices & Adding PCF8563 Binding (#489)

* Added PCF8563 Binding

* add number tool

* update readme

* remove namespace

* refactoring completion

* resolve comments

src/devices/Common/Iot/Device/Common/NumberHelper.cs

@@ -0,0 +1,32 @@
+// 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.Common
+{
+    /// <summary>
+    /// Helpers for number.
+    /// </summary>
+    internal static class NumberHelper
+    {
+        /// <summary>
+        /// BCD To decimal
+        /// </summary>
+        /// <param name="bcd">BCD Code</param>
+        /// <returns>decimal</returns>
+        public static int Bcd2Dec(byte bcd)
+        {
+            return ((bcd >> 4) * 10) + (bcd % 16);
+        }
+
+        /// <summary>
+        /// Decimal To BCD
+        /// </summary>
+        /// <param name="dec">decimal</param>
+        /// <returns>BCD Code</returns>
+        public static byte Dec2Bcd(int dec)
+        {
+            return (byte)(((dec / 10) << 4) + (dec % 10));
+        }
+    }
+}

src/devices/Rtc/Devices/Ds1307/Ds1307.cs

@@ -0,0 +1,88 @@
+// 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 Iot.Device.Common;
+
+namespace Iot.Device.Rtc
+{
+    /// <summary>
+    /// Realtime Clock DS1307
+    /// </summary>
+    public class Ds1307 : RtcBase
+    {
+        /// <summary>
+        /// DS1307 Default I2C Address
+        /// </summary>
+        public const byte DefaultI2cAddress = 0x68;
+
+        private I2cDevice _i2cDevice;
+
+        /// <summary>
+        /// Creates a new instance of the DS1307
+        /// </summary>
+        /// <param name="i2cDevice">The I2C device used for communication.</param>
+        public Ds1307(I2cDevice i2cDevice)
+        {
+            _i2cDevice = i2cDevice;
+        }
+
+        /// <summary>
+        /// Read Time from DS1307
+        /// </summary>
+        /// <returns>DS1307 Time</returns>
+        protected override DateTime ReadTime()
+        {
+            Span<byte> readBuffer = stackalloc byte[7];
+
+            // Read all registers at the same time
+            _i2cDevice.WriteByte((byte)Ds1307Register.RTC_SEC_REG_ADDR);
+            _i2cDevice.Read(readBuffer);
+
+            // Details in the Datasheet P8
+            return new DateTime(2000 + NumberHelper.Bcd2Dec(readBuffer[6]), 
+                                NumberHelper.Bcd2Dec(readBuffer[5]), 
+                                NumberHelper.Bcd2Dec(readBuffer[4]), 
+                                NumberHelper.Bcd2Dec(readBuffer[2]),
+                                NumberHelper.Bcd2Dec(readBuffer[1]), 
+                                NumberHelper.Bcd2Dec((byte)(readBuffer[0] & 0b_0111_1111)));
+        }
+
+        /// <summary>
+        /// Set DS1307 Time
+        /// </summary>
+        /// <param name="time">Time</param>
+        protected override void SetTime(DateTime time)
+        {
+            Span<byte> writeBuffer = stackalloc byte[8];
+
+            writeBuffer[0] = (byte)Ds1307Register.RTC_SEC_REG_ADDR;
+
+            // Details in the Datasheet P8
+            // | bit 7: CH | bit 6-0: sec |
+            writeBuffer[1] = (byte)(NumberHelper.Dec2Bcd(time.Second) & 0b_0111_1111);
+            writeBuffer[2] = NumberHelper.Dec2Bcd(time.Minute);
+            // | bit 7: 0 | bit 6: 12/24 hour | bit 5-0: hour |
+            writeBuffer[3] = (byte)(NumberHelper.Dec2Bcd(time.Hour) & 0b_0011_1111);
+            writeBuffer[4] = NumberHelper.Dec2Bcd((int)time.DayOfWeek + 1);
+            writeBuffer[5] = NumberHelper.Dec2Bcd(time.Day);
+            writeBuffer[6] = NumberHelper.Dec2Bcd(time.Month);
+            writeBuffer[7] = NumberHelper.Dec2Bcd(time.Year - 2000);
+
+            _i2cDevice.Write(writeBuffer);
+        }
+
+        /// <summary>
+        /// Cleanup
+        /// </summary>
+        protected override void Dispose(bool disposing)
+        {
+            _i2cDevice?.Dispose();
+            _i2cDevice = null;
+
+            base.Dispose(disposing);
+        }
+    }
+}