Using PROGMEM for custom chars - HOWTO

[smartroad]

Hi All!

I thought I would add this here for anyone wanting to move any custom characters from RAM to ROM and save what limited space is available on the chip for more important things! I also want to say this is not my idea, but I got it from https://forum.arduino.cc/index.php?topic=519102.0 and modified it for this library.

in LiquidCrystal_I2C.cpp add the following (I added under the exisiting LiquidCrystal_I2C::creatChar):

void LiquidCrystal_I2C::createChar_P (uint8_t addr, const uint8_t *bitmap)
{
    uint8_t n;
    command (LCD_SETCGRAMADDR | ((addr % 8) * 8));
    for (n = 0; n < 8; n++) {
        write (pgm_read_byte (bitmap + n));
    }
}

then further down, under the section saying // Alias functions I added:

void LiquidCrystal_I2C::createChar_P (uint8_t addr, const char *bitmap)
{
    createChar_P (addr, (const uint8_t *)(bitmap));
}

Save and close LiquidCrystal_I2C.cpp then open LiquidCrystal_I2C.h Under where it says public: add:

  void createChar_P (uint8_t, const char *);
  void createChar_P (uint8_t, const uint8_t *);

Save and close. Optional but useful Open the keywords.txt file and add in CreateChar_P KEYWORD2 (the space between must be a TAB mark not a space) This will colour the text when you declare it in you sketch. Not essential but useful i think.

At this point you can open up in the Arduino IDE and use.

EXAMPLE OF USE

const byte face[8] PROGMEM = {
  B01110,
  B10001,
  B11011,
  B10001,
  B11011,
  B10101,
  B10001,
  B01110,
};

lcd.createChar_P(0, face);
lcd.write(0);

Hope this helps!!

[modarsoos]

Good job