Added CreateCustomCharacter().

characterlcd.mod/characterlcd.bmx

@@ -603,6 +603,55 @@ Type THd44780 Implements IDisposable
 		SendCommand((EDisplayShift.Command | EDisplayShift.Display | EDisplayShift.Right).Ordinal())
 	End Method
 	
+	Rem
+	bbdoc: Fill one of the 8 CGRAM locations (character codes 0 - 7) with custom characters.
+	about: The custom characters also occupy character codes 8 - 15.
+	You can find help designing characters at https://www.quinapalus.com/hd44780udg.html
+	
+	The datasheet description for custom characters is very difficult to follow. Here is a rehash of the technical details that is hopefully easier:
+	> Only 6 bits of addresses are available for character ram. That makes for 64 bytes of
+	> available character data. 8 bytes of data are used for each character, which is where
+	> the 8 total custom characters comes from (64/8).
+	> 
+	> Each byte corresponds to a character line. Characters are only 5 bits wide so only
+	> bits 0-4 are used for display. Whatever is in bits 5-7 is just ignored. Store bits
+	> there if it makes you happy, but it won't impact the display. '1' is on, '0' is off.
+	> 
+	> In the built-in characters the 8th byte is usually empty as this is where the underline
+	> cursor will be if enabled. You can put data there if you like, which gives you the full
+	> 5x8 character. The underline cursor just turns on the entire bottom row.
+	> 
+	> 5x10 mode is effectively useless as displays aren't available that utilize it. In 5x10
+	> mode *16* bytes of data are used for each character. That leaves room for only *4*
+	> custom characters. The first character is addressable from code 0, 1, 8, and 9. The
+	> second is 2, 3, 10, 11 and so on...
+	> 
+	> In this mode *11* bytes of data are actually used for the character data, which
+	> effectively gives you a 5x11 character, although typically the last line is blank to
+	> leave room for the underline cursor. Why the modes are referred to as 5x8 and 5x10 as
+	> opposed to 5x7 and 5x10 or 5x8 and 5x11 is a mystery. In an early pre-release data
+	> book 5x7 and 5x10 is used (Advance Copy #AP4 from July 1985). Perhaps it was a
+	> marketing change?
+	> 
+	> As only 11 bytes are used in 5x10 mode, but 16 bytes are reserved, the last 5 bytes
+	> are useless. The datasheet helpfully suggests that you can store your own data there.
+	> The same would be true for bits 5-7 of lines that matter for both 5x8 and 5x10.
+	End Rem
+	Method CreateCustomCharacter(location:Byte, characterMap:Byte[])
+		If location > 7 Then
+			Throw New TArgumentOutOfRangeException("location")
+		End If
+		
+		If characterMap.Length <> 8 Then
+			Throw New TArgumentException("characterMap")
+		End If
+		
+		' The character address is set in bits 3-5 of the command byte
+		SendCommand(SET_CG_RAM_ADDRESS_COMMAND | (location Shl 3))
+		SendData(characterMap, characterMap.Length)
+	End Method
+	
+	
 	Rem
 	bbdoc: Writes text to the display.
 	End Rem