Introduce wait states for some commands (#1466)

Otherwise, the display initialization might fail, leaving
the display in an undefined state

src/devices/CharacterLcd/Hd44780.cs

@@ -103,18 +103,13 @@ namespace Iot.Device.CharacterLcd
             _displayControl |= DisplayControl.DisplayOn;
             _displayMode |= DisplayEntryMode.Increment;
 
-            ReadOnlySpan<byte> commands = stackalloc byte[]
-            {
-                // Function must be set first to ensure that we always have the basic
-                // instruction set selected. (See PCF2119x datasheet Function_set note
-                // for one documented example of where this is necessary.)
-                (byte)_displayFunction,
-                (byte)_displayControl,
-                (byte)_displayMode,
-                ClearDisplayCommand
-            };
-
-            SendCommands(commands);
+            // Function must be set first to ensure that we always have the basic
+            // instruction set selected. (See PCF2119x datasheet Function_set note
+            // for one documented example of where this is necessary.)
+            SendCommandAndWait((byte)_displayFunction);
+            SendCommandAndWait((byte)_displayControl);
+            SendCommandAndWait((byte)_displayMode);
+            SendCommandAndWait(ClearDisplayCommand);
         }
 
         /// <summary>
@@ -138,6 +133,14 @@ namespace Iot.Device.CharacterLcd
         /// <param name="command">Byte representing the command to be sent</param>
         protected void SendCommand(byte command) => _lcdInterface.SendCommand(command);
 
+        /// <summary>
+        /// The initialization sequence and some other complex commands should be sent with delays, or the display may
+        /// behave unexpectedly. It may show random, blinking characters
+        /// or display text very faintly only.
+        /// </summary>
+        /// <param name="command">The command to send</param>
+        protected void SendCommandAndWait(byte command) => _lcdInterface.SendCommandAndWait(command);
+
         /// <summary>
         /// Sends data to the device
         /// </summary>
@@ -259,7 +262,7 @@ namespace Iot.Device.CharacterLcd
         public bool DisplayOn
         {
             get => (_displayControl & DisplayControl.DisplayOn) > 0;
-            set => SendCommand((byte)(value ? _displayControl |= DisplayControl.DisplayOn
+            set => SendCommandAndWait((byte)(value ? _displayControl |= DisplayControl.DisplayOn
                 : _displayControl &= ~DisplayControl.DisplayOn));
         }
 
@@ -269,7 +272,7 @@ namespace Iot.Device.CharacterLcd
         public bool UnderlineCursorVisible
         {
             get => (_displayControl & DisplayControl.CursorOn) > 0;
-            set => SendCommand((byte)(value ? _displayControl |= DisplayControl.CursorOn
+            set => SendCommandAndWait((byte)(value ? _displayControl |= DisplayControl.CursorOn
                 : _displayControl &= ~DisplayControl.CursorOn));
         }
 
@@ -279,7 +282,7 @@ namespace Iot.Device.CharacterLcd
         public bool BlinkingCursorVisible
         {
             get => (_displayControl & DisplayControl.BlinkOn) > 0;
-            set => SendCommand((byte)(value ? _displayControl |= DisplayControl.BlinkOn
+            set => SendCommandAndWait((byte)(value ? _displayControl |= DisplayControl.BlinkOn
                 : _displayControl &= ~DisplayControl.BlinkOn));
         }
 
@@ -289,7 +292,7 @@ namespace Iot.Device.CharacterLcd
         public bool AutoShift
         {
             get => (_displayMode & DisplayEntryMode.DisplayShift) > 0;
-            set => SendCommand((byte)(value ? _displayMode |= DisplayEntryMode.DisplayShift
+            set => SendCommandAndWait((byte)(value ? _displayMode |= DisplayEntryMode.DisplayShift
                 : _displayMode &= ~DisplayEntryMode.DisplayShift));
         }
 
@@ -299,7 +302,7 @@ namespace Iot.Device.CharacterLcd
         public bool Increment
         {
             get => (_displayMode & DisplayEntryMode.Increment) > 0;
-            set => SendCommand((byte)(value ? _displayMode |= DisplayEntryMode.Increment
+            set => SendCommandAndWait((byte)(value ? _displayMode |= DisplayEntryMode.Increment
                 : _displayMode &= ~DisplayEntryMode.Increment));
         }
 
@@ -393,14 +396,13 @@ namespace Iot.Device.CharacterLcd
         /// </remarks>
         public void Write(string text)
         {
-            byte[] buffer = ArrayPool<byte>.Shared.Rent(text.Length);
+            Span<byte> buffer = stackalloc byte[text.Length];
             for (int i = 0; i < text.Length; ++i)
             {
                 buffer[i] = (byte)text[i];
             }
 
-            SendData(new ReadOnlySpan<byte>(buffer, 0, text.Length));
-            ArrayPool<byte>.Shared.Return(buffer);
+            SendData(buffer);
         }
 
         /// <summary>

src/devices/CharacterLcd/LcdInterface.I2c4Bit.cs

@@ -54,7 +54,7 @@ namespace Iot.Device.CharacterLcd
                 {
                     _backlightOn = value;
                     // Need to send a command to make this happen immediately.
-                    SendCommand(0);
+                    SendCommandAndWait(0);
                 }
             }
 
@@ -87,7 +87,7 @@ namespace Iot.Device.CharacterLcd
                 SendCommandAndWait(LCD_ENTRYMODESET | LCD_ENTRYLEFT);
             }
 
-            private void SendCommandAndWait(byte command)
+            public override void SendCommandAndWait(byte command)
             {
                 // Must not run the init sequence to fast or undefined behavior may occur
                 SendCommand(command);

src/devices/CharacterLcd/LcdInterface.cs

@@ -5,6 +5,7 @@ using System;
 using System.Device;
 using System.Device.Gpio;
 using System.Device.I2c;
+using System.Threading;
 
 namespace Iot.Device.CharacterLcd
 {
@@ -81,6 +82,19 @@ namespace Iot.Device.CharacterLcd
         /// <param name="values">Each byte represents command to be send</param>
         public abstract void SendCommands(ReadOnlySpan<byte> values);
 
+        /// <summary>
+        /// The initialization sequence and some other complex commands should be sent with delays, or the display may
+        /// behave unexpectedly. It may show random, blinking characters
+        /// or display text very faintly only.
+        /// </summary>
+        /// <param name="command">The command to send</param>
+        public virtual void SendCommandAndWait(byte command)
+        {
+            // Must not run the init sequence to fast or undefined behavior may occur
+            SendCommand(command);
+            Thread.Sleep(1);
+        }
+
         /// <summary>
         /// True if device uses 8-bits for communication, false if device uses 4-bits
         /// </summary>