Electronic – Displaying a custom character on 2×16 LCD

clcd

I have written a working LCD driver for a NHD‐0212WH‐ATGH‐JT and I would like to add the possibility to create your own custom characters.

Through some research I understood that I need to write a byte for each row in the CGRAM in specific positions and then point to that position when trying to write a character.

I did the following but it doesn't seem to be working:

The array of char for the bytes to write to CGRAM were obtained with online tools such as HD44780 LCD User-Defined Graphics. The functions and commands don't seem to be the problem as I write every other ASCII characters just fine.

char myCustomCharacter[8] = {0x0,0x1,0x3,0x16,0x1c,0x8,0x0};

void createCharacter(unsigned char location, unsigned char[] bytes){
    writeCommand(0x40+(location*8));
    writeData(bytes[0]);
    writeData(bytes[1]);
    writeData(bytes[2]);
    writeData(bytes[3]);
    writeData(bytes[4]);
    writeData(bytes[5]);
    writeData(bytes[6]);
    writeData(bytes[7]);
}

Then in some test main:

int main(void){
    initLCD();
    createCharacter(1, myCustomCharacter);
    setCursor(0, 0);
    writeCharacter('A'); //This work just fine, the A is displayed as expected
    writeCharacter(0x08); //Doesn't work, I don't see the character I stored in the CGRAM at the 1st position. Any standard ASCII character still works just fine.
}

How do I access the custom character as if it was just another ASCII character and how do I know I have correctly written the byte into the CGRAM?

Best Answer

The following line adds a custom character to a CGRAM location 1.

createCharacter(1, myCustomCharacter);

The problem with your code was that you told the controller to write a custom character stored at location 8. The writing code should instead look like this.

writeCharacter(0x01)
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