Creating custom characters for LCD printing

Hi all ! I'm trying to create custom characters for my LCD shield. It's a 16x2 screen with 8x5 characters, and I drive it with the Hd44780Lcd class. I found a link that seems useful (http://www.quinapalu...hd44780udg.html) to translate a pixel matrix into numeric elements, but I don't understand how I should set my custom characters. I tried to write a byte array using hexadecimal values but it doesn't work. If somebody has an idea to solve this problem, I would really appreciate it thank you very much !

Hi Terb,

I've done that before, for this project:

The code isn't published yet, but the method for the custom characters is this one:

       public static void main()
       {
            // To play snake on a 2x16 LCD, we need 7 custom characters (0x00 to 0x06):
            _CustomizeCharacter(0x00, new byte[] { 0x00, 0x00, 0x00, 0x00, 0x00, 0x0e, 0x0e, 0x00 }); // b000: ₒ     (fruit at the bottom)
            _CustomizeCharacter(0x01, new byte[] { 0x00, 0x0e, 0x0e, 0x00, 0x00, 0x00, 0x00, 0x00 }); // b001: °     (fruit at the top)
            _CustomizeCharacter(0x02, new byte[] { 0x1f, 0x1f, 0x1f, 0x1f, 0x00, 0x00, 0x00, 0x00 }); // b010: ▀     (snake at the top)
            _CustomizeCharacter(0x03, new byte[] { 0x1f, 0x1f, 0x1f, 0x1f, 0x00, 0x0e, 0x0e, 0x00 }); // b011: ▀ + ₒ (snake at the top + fruit at the bottom)
            _CustomizeCharacter(0x04, new byte[] { 0x00, 0x00, 0x00, 0x00, 0x1f, 0x1f, 0x1f, 0x1f }); // b100: ▄     (snake at the bottom)
            _CustomizeCharacter(0x05, new byte[] { 0x00, 0x0e, 0x0e, 0x00, 0x1f, 0x1f, 0x1f, 0x1f }); // b101: ▄ + ° (snake at the bottom + fruit at the top)
            _CustomizeCharacter(0x06, new byte[] { 0x1f, 0x1f, 0x1f, 0x1f, 0x1f, 0x1f, 0x1f, 0x1f }); // b110: █     (snake at the bottom + snake at the top)
       }

        /// <summary>
        /// Creates a customized character on a HD44780 LCD
        /// </summary>
        /// <param name="Index">Character index (0 to 7)</param>
        /// <param name="Character">Character bitmap</param>
        private static void _CustomizeCharacter(int Index, byte[] CharacterBitmap)
        {
            if (Index < 0 || Index > 7) throw new IndexOutOfRangeException("Index must be a value from 0 to 7");
            if (CharacterBitmap.Length != 8) throw new ArgumentOutOfRangeException("CharacterBitmap must have 8 byte values");
            _disp.Write((byte)(0x40 + 8 * Index), true); // Set CGRAM Address
            _disp.Write(CharacterBitmap);                // Writes the character
            _disp.Write(0x80, true);                     // Set DDRAM Address
        }

Maybe that'll help you?

_disp is an instance of Toolbox.NETMF.Hardware.Hd44780Lcd

Hi Stefan, thank you very much ! I use the same class so it will be easy to try your method on my program. thank you again, I'll try this today and let you know By the way I watched your video, it's really great. I like the idea of using a 2-lines screen and custom characters to use it as a 4-line screen.

By the way I watched your video, it's really great. I like the idea of using a 2-lines screen and custom characters to use it as a 4-line screen.

Thanks!

I hope to release the code next week

I just tried this way to set and display custom characters, it works perfectly. Thank you again Stefan ! your help is really precious to me. do you know how many custom characters can be set on these LCD screens ?

do you know how many custom characters can be set on these LCD screens ?

Yep, only 8
Hence this line of code:

if (Index < 0 || Index > 7) throw new IndexOutOfRangeException("Index must be a value from 0 to 7");

I wish it could do more, but it's still very nice for such cheap displays I reccon.

Yes, that's what I understood. I need way more than 8 custom chars, but I think I can deal with 8 custom chars displayed at a given time. I think I will do something like redefine the custom chars dynamically. should work By the way, I'm ok with you, these screens are pretty cheap and it's a good thing to have 8 custom chars. way better than nothing

Yes, that's what I understood. I need way more than 8 custom chars, but I think I can deal with 8 custom chars displayed at a given time. I think I will do something like redefine the custom chars dynamically. should work

That's a good thing to do; dynamically. My app will do that too. While playing the game, it'll contain 8 characters required for the snake, but I will also have a graphical splash screen, composed with 8 other characters

Great ! I'd love to see this spash screen My goal is to display big numbers but I will have no more than 2 numbers at the same time. Each digit will be displayed on 4 characters (2x2 matrix) so I'm fine with 8 user-defined characters at a given time. I'd like to add other fancy characters but the 8 chars limit won't allow me that. Not a big issue.

I tried the dynamic user-defined characters, it works fine. One interesting point (at least for my project) is that there is no need to write the character after redefying it, if the position doesn't change. It means that I will write my 8 custom characters at fixed positions on the LCD screen, and I will change the values by dynamically redefying the characters, directly in the LCD controller RAM. I'm writing a class to manage all these operations, and I will only have to change the values with something like this :

Lcd.WriteBigCharacters("14");

Here it is ! a short demo video showing every character (number) several times over a 1-minute loop : http://rutube.ru/vid...79d27361df83d1/ it works by dynamic characters definition, as we said before.

Here it is ! a short demo video showing every character (number) several times over a 1-minute loop : http://rutube.ru/vid...79d27361df83d1/
it works by dynamic characters definition, as we said before.

Nice use of the dynamic characters, terb.

Chris

thanks Chris

Hi there !
just a quick update : a simple waiting screen (will be used when the GPS will be searching for satellites). It's a 16-steps sequence loop that uses dynamic custom characters definition. It uses 20 custom characters (+ 40 other ones for the numbers) in total, 8 at a given time.

here it is : http://rutube.ru/vid...b238eb5298c8c36

Hi Terb,

I've done that before, for this project:

The code isn't published yet, but the method for the custom characters is this one:

       public static void main()       {            // To play snake on a 2x16 LCD, we need 7 custom characters (0x00 to 0x06):            _CustomizeCharacter(0x00, new byte[] { 0x00, 0x00, 0x00, 0x00, 0x00, 0x0e, 0x0e, 0x00 }); // b000: ₒ     (fruit at the bottom)            _CustomizeCharacter(0x01, new byte[] { 0x00, 0x0e, 0x0e, 0x00, 0x00, 0x00, 0x00, 0x00 }); // b001: °     (fruit at the top)            _CustomizeCharacter(0x02, new byte[] { 0x1f, 0x1f, 0x1f, 0x1f, 0x00, 0x00, 0x00, 0x00 }); // b010: ▀     (snake at the top)            _CustomizeCharacter(0x03, new byte[] { 0x1f, 0x1f, 0x1f, 0x1f, 0x00, 0x0e, 0x0e, 0x00 }); // b011: ▀ + ₒ (snake at the top + fruit at the bottom)            _CustomizeCharacter(0x04, new byte[] { 0x00, 0x00, 0x00, 0x00, 0x1f, 0x1f, 0x1f, 0x1f }); // b100: ▄     (snake at the bottom)            _CustomizeCharacter(0x05, new byte[] { 0x00, 0x0e, 0x0e, 0x00, 0x1f, 0x1f, 0x1f, 0x1f }); // b101: ▄ + ° (snake at the bottom + fruit at the top)            _CustomizeCharacter(0x06, new byte[] { 0x1f, 0x1f, 0x1f, 0x1f, 0x1f, 0x1f, 0x1f, 0x1f }); // b110: █     (snake at the bottom + snake at the top)       }        /// <summary>        /// Creates a customized character on a HD44780 LCD        /// </summary>        /// <param name="Index">Character index (0 to 7)</param>        /// <param name="Character">Character bitmap</param>        private static void _CustomizeCharacter(int Index, byte[] CharacterBitmap)        {            if (Index < 0 || Index > 7) throw new IndexOutOfRangeException("Index must be a value from 0 to 7");            if (CharacterBitmap.Length != 8) throw new ArgumentOutOfRangeException("CharacterBitmap must have 8 byte values");            _disp.Write((byte)(0x40 + 8 * Index), true); // Set CGRAM Address            _disp.Write(CharacterBitmap);                // Writes the character            _disp.Write(0x80, true);                     // Set DDRAM Address        }

Maybe that'll help you?

_disp is an instance of Toolbox.NETMF.Hardware.Hd44780Lcd

 

Hi,

 

I just bought the Adafruit 16x2 LCD with a RCB LCD in a package and it works fine for standard character.

Now I tried you code above, but nothing is shown...do I have to call the character somehow to actually write it to the screen?

 

Thanks

Hi,

 

I just bought the Adafruit 16x2 LCD with a RCB LCD in a package and it works fine for standard character.

Now I tried you code above, but nothing is shown...do I have to call the character somehow to actually write it to the screen?

 

Thanks

 

Yes, you must call the character. You can best check out this sample code:

http://netmftoolbox....ew/21723#339006

 

        /// <summary>        /// Shows the splash screen        /// </summary>        public static void Splash()        {            _disp.ClearDisplay();            _NetduinoLogo();            _disp.Write(" HD44780  Snake");            _disp.ChangePosition(1, 2);            _disp.Write("for ");            _disp.Write(new byte[] { 0, 1, 2, 3, 4, 5, 0, 6 }, false);        }

The last line writes the characters by their index.