Custom characters on HD44780 display (Nerdkit)

It took me really a lot of time to turn my Nerdkit into a Pixel Art Machine.

Because of that I wanted to share my experience with the community.

The following code shows one custom character on your nerdkit display.

#define F_CPU 14745600
 
#include <stdio.h>
 
#include <avr/io.h>
#include <avr/pgmspace.h>
#include <inttypes.h>
 
#include <inttypes.h>
#include <string.h>
 
#include <util/delay.h>
#include "../libnerdkits/delay.h"
#include "../libnerdkits/lcd.h"
 
int main(void) {
 
  // fire up the LCD
  lcd_init();
  lcd_home();
 
lcd_set_type_command();     // Change into command mode
lcd_write_byte(0x40);       // Change to CGRAM to store custom character - at 0x00
lcd_set_type_data();        // Change into data mode
 
lcd_write_byte(0x00);       // Send Hexa Bytes of Custom Character Begin
lcd_write_byte(0x0E);
lcd_write_byte(0x1F);
lcd_write_byte(0x1F);
lcd_write_byte(0x1F);
lcd_write_byte(0x0E);
lcd_write_byte(0x00);
lcd_write_byte(0x00);       // Send Hexa Bytes of Custom Character End
 
lcd_set_type_command();     // Change into command mode
lcd_write_byte(0x80);       // Change to DDRAM
 
lcd_set_type_data();
lcd_write_byte(0x00);       // Show stored custom character on lcd screen
 
  // busy loop
  while(1) {
 
  // do nothing
  }
 
  return 0;
}

This part was for a better understanding how things have to be written and read from the CGRAM.

Please check your makefile for this project.
You have to change from '-Os' to '-O0' in the makefile, or else your display writes anytime into the first line.

To get a clear declaration of the array, you also have to change the following code into your makefile:

Makefile

avr-objcopy -j .text -j .data -O ihex lnino_eval_board.o lnino_eval_board.hex

I have modified the original nerdkit LCD library to have a more comfortable use of custom characters.

char pattern01[8]={14,17,17,14,4,6,4,6}; // Key Pattern

lcd_createChar(0, pattern01); // Create Char on position 0x00
lcd_loadCharSingle(0x00); // Loads the Char 0x00 on the current Cursor Position
lcd_loadChar(0,19,0x00); // Loads the Char 0x00 on row 0, column 19

You can convert your Images to Numbers on the following Website:
http://www.quinapalus.com/hd44780udg.html

The complete modified nerdkit lcd library is attached here:

lcd.c

// lcd.c
// for NerdKits
// This email address is being protected from spambots. You need JavaScript enabled to view it.
//
// PIN DEFINITIONS:
//
//
// PD2-5 -- LCD DB4-7 (pins 11-14) (was PB3-6)
// PD6 -- LCD E (pin 6) (was PA5)
// PD7 -- LCD RS (pin 4) (was PA4)
 
#include <avr/io.h>
#include <avr/pgmspace.h>
#include <inttypes.h>
#include <stdio.h>
 
#include "lcd.h"
#include "delay.h"
 
// lcd_set_type_data()
void lcd_set_type_data() {
  PORTD |= (1<<PD7);
}
 
// lcd_set_type_command()
void lcd_set_type_command() {
  PORTD &= ~(1<<PD7);
}
 
// lcd_createChar()
void lcd_createChar(uint8_t location, char charmap[]) {
  int i = 0;
  location &= 0x7;            // 8 possible characters regarding to 1Byte availability
  lcd_set_type_command();      // Change into command mode
  lcd_write_byte(0x40 | (location << 3));
  lcd_set_type_data();         // Change into data mode
 
  for (i=0; i<8; i++) {
   lcd_write_byte(charmap[i]);
  }
 
  lcd_set_type_command();      // Change into command mode
  lcd_write_byte(0x80);         // Change to DDRAM
  lcd_set_type_data();         // Change into data mode
}
 
// lcd_loadChar()
void lcd_loadChar(uint8_t row_position, uint8_t column_position, char mem_location) {
  lcd_goto_position(row_position, column_position);
  lcd_write_byte_data(mem_location);
}
 
// lcd_loadCharSingle()
void lcd_loadCharSingle(char mem_location) {
  lcd_write_byte_data(mem_location);
}
 
// lcd_write_nibble(...)
void lcd_write_nibble(char c) {
 
  // NOTE: only 2 or 3 work in the delays here.
 
  // set data
  PORTD &= ~(0x0f << 2);
  PORTD |= (c&0x0f) << 2;
 
  // E high
  PORTD |= (1<<PD6);
  delay_us(1);
  // E low
  PORTD &= ~(1<<PD6);
  delay_us(1);
 
}
 
void lcd_write_byte_data(char c) {
  lcd_set_type_data();
  lcd_write_nibble( (c >> 4) & 0x0f );
  lcd_write_nibble( c & 0x0f );
  delay_us(80);
}
 
void lcd_write_byte_command(char c) {
  lcd_set_type_command();
  lcd_write_nibble( (c >> 4) & 0x0f );
  lcd_write_nibble( c & 0x0f );
  delay_us(80);
}
 
void lcd_write_byte(char c) {
  lcd_write_nibble( (c >> 4) & 0x0f );
  lcd_write_nibble( c & 0x0f );
  delay_us(80);
}
 
void lcd_clear_and_home() {
  lcd_set_type_command();
  lcd_write_byte(0x01);
  delay_ms(50);
  lcd_write_byte(0x02);
  delay_ms(50);
}
 
void lcd_home() {
  lcd_set_type_command();
  lcd_write_byte(0x02);
  delay_ms(50);
}
 
void lcd_write_data(char c) {
  lcd_set_type_data();
  lcd_write_byte(c);
}
 
// lcd_write_int16
void lcd_write_int16(int16_t in) {
  uint8_t started = 0;
 
  uint16_t pow = 10000;
 
  if(in < 0) {
    lcd_write_data('-');
    in = -in;
  }
 
  while(pow >= 1) {
    if(in / pow > 0 || started || pow==1) {
      lcd_write_data((uint8_t) (in/pow) + '0');
      started = 1;
      in = in % pow;
    }
 
    pow = pow / 10;
  }
 
}
 
 
// lcd_write_int16_centi
// assumes that its measured in centi-whatevers
void lcd_write_int16_centi(int16_t in) {
  uint8_t started = 0;
 
  uint16_t pow = 10000;
 
  if(in < 0) {
    lcd_write_data('-');
    in = -in;
  }
 
  while(pow >= 1) {
    if(in / pow > 0 || started || pow==1) {
      lcd_write_data((uint8_t) (in/pow) + '0');
      started = 1;
      in = in % pow;
    }
 
    if(pow == 100) {
      if(!started) {
        lcd_write_data('0');
      }
      lcd_write_data('.');
      started = 1;
    }
 
    pow = pow / 10;
  }
 
}
 
void lcd_write_string(const char *x) {
  // assumes x is in program memory
  while(pgm_read_byte(x) != 0x00)
    lcd_write_data(pgm_read_byte(x++));
}
 
void lcd_goto_position(uint8_t row, uint8_t col) {
  lcd_set_type_command();
 
  // 20x4 LCD: offsets 0, 0x40, 20, 0x40+20
  uint8_t row_offset = 0;
  switch(row) {
    case 0: row_offset = 0; break;
    case 1: row_offset = 0x40; break;
    case 2: row_offset = 20; break;
    case 3: row_offset = 0x40+20; break;
  }
 
 
  lcd_write_byte(0x80 | (row_offset + col));
}
 
void lcd_line_one()   { lcd_goto_position(0, 0); }
void lcd_line_two()   { lcd_goto_position(1, 0); }
void lcd_line_three() { lcd_goto_position(2, 0); }
void lcd_line_four()  { lcd_goto_position(3, 0); }
 
// lcd_init()
void lcd_init() {
  // set pin driver directions
  // (output on PD7,PD6, and PD3-6)
  DDRD |= 0xfc;
 
  // wait 100msec
  delay_ms(100);
  lcd_set_type_command();
 
  // do reset
  lcd_write_nibble(0x03);
  delay_ms(6);
  lcd_write_nibble(0x03);
  delay_us(250);
  lcd_write_nibble(0x03);
  delay_us(250);
 
  // write 0010 (data length 4 bits)
  lcd_write_nibble(0x02);
  // set to 2 lines, font 5x8
  lcd_write_byte(0x28);
  // disable LCD
  //lcd_write_byte(0x08);
  // enable LCD
  lcd_write_byte(0x0c);
  // clear display
  lcd_write_byte(0x01);
  delay_ms(5);
  // enable LCD
  lcd_write_byte(0x0c);
  // set entry mode
  lcd_write_byte(0x06);
 
  // set cursor/display shift
  lcd_write_byte(0x14);
 
  // clear and home
  lcd_clear_and_home();
}
 
int lcd_putchar(char c, FILE *stream) {
  lcd_write_data(c);
  return 0;
}

lcd.h

// lcd.c
// for NerdKits
// This email address is being protected from spambots. You need JavaScript enabled to view it.
//
// PIN DEFINITIONS:
//
//
// PD2-5 -- LCD DB4-7 (pins 11-14) (was PB3-6)
// PD6 -- LCD E (pin 6) (was PA5)
// PD7 -- LCD RS (pin 4) (was PA4)
 
#include <avr/io.h>
#include <avr/pgmspace.h>
#include <inttypes.h>
#include <stdio.h>
 
#include "lcd.h"
#include "delay.h"
 
// lcd_set_type_data()
void lcd_set_type_data() {
  PORTD |= (1<<PD7);
}
 
// lcd_set_type_command()
void lcd_set_type_command() {
  PORTD &= ~(1<<PD7);
}
 
// lcd_createChar()
void lcd_createChar(uint8_t location, char charmap[]) {
  int i = 0;
  location &= 0x7;            // 8 possible characters regarding to 1Byte availability
  lcd_set_type_command();      // Change into command mode
  lcd_write_byte(0x40 | (location << 3));
  lcd_set_type_data();         // Change into data mode
 
  for (i=0; i<8; i++) {
   lcd_write_byte(charmap[i]);
  }
 
  lcd_set_type_command();      // Change into command mode
  lcd_write_byte(0x80);         // Change to DDRAM
  lcd_set_type_data();         // Change into data mode
}
 
// lcd_loadChar()
void lcd_loadChar(uint8_t row_position, uint8_t column_position, char mem_location) {
  lcd_goto_position(row_position, column_position);
  lcd_write_byte_data(mem_location);
}
 
// lcd_loadCharSingle()
void lcd_loadCharSingle(char mem_location) {
  lcd_write_byte_data(mem_location);
}
 
// lcd_write_nibble(...)
void lcd_write_nibble(char c) {
 
  // NOTE: only 2 or 3 work in the delays here.
 
  // set data
  PORTD &= ~(0x0f << 2);
  PORTD |= (c&0x0f) << 2;
 
  // E high
  PORTD |= (1<<PD6);
  delay_us(1);
  // E low
  PORTD &= ~(1<<PD6);
  delay_us(1);
 
}
 
void lcd_write_byte_data(char c) {
  lcd_set_type_data();
  lcd_write_nibble( (c >> 4) & 0x0f );
  lcd_write_nibble( c & 0x0f );
  delay_us(80);
}
 
void lcd_write_byte_command(char c) {
  lcd_set_type_command();
  lcd_write_nibble( (c >> 4) & 0x0f );
  lcd_write_nibble( c & 0x0f );
  delay_us(80);
}
 
void lcd_write_byte(char c) {
  lcd_write_nibble( (c >> 4) & 0x0f );
  lcd_write_nibble( c & 0x0f );
  delay_us(80);
}
 
void lcd_clear_and_home() {
  lcd_set_type_command();
  lcd_write_byte(0x01);
  delay_ms(50);
  lcd_write_byte(0x02);
  delay_ms(50);
}
 
void lcd_home() {
  lcd_set_type_command();
  lcd_write_byte(0x02);
  delay_ms(50);
}
 
void lcd_write_data(char c) {
  lcd_set_type_data();
  lcd_write_byte(c);
}
 
// lcd_write_int16
void lcd_write_int16(int16_t in) {
  uint8_t started = 0;
 
  uint16_t pow = 10000;
 
  if(in < 0) {
    lcd_write_data('-');
    in = -in;
  }
 
  while(pow >= 1) {
    if(in / pow > 0 || started || pow==1) {
      lcd_write_data((uint8_t) (in/pow) + '0');
      started = 1;
      in = in % pow;
    }
 
    pow = pow / 10;
  }
 
}
 
 
// lcd_write_int16_centi
// assumes that its measured in centi-whatevers
void lcd_write_int16_centi(int16_t in) {
  uint8_t started = 0;
 
  uint16_t pow = 10000;
 
  if(in < 0) {
    lcd_write_data('-');
    in = -in;
  }
 
  while(pow >= 1) {
    if(in / pow > 0 || started || pow==1) {
      lcd_write_data((uint8_t) (in/pow) + '0');
      started = 1;
      in = in % pow;
    }
 
    if(pow == 100) {
      if(!started) {
        lcd_write_data('0');
      }
      lcd_write_data('.');
      started = 1;
    }
 
    pow = pow / 10;
  }
 
}
 
void lcd_write_string(const char *x) {
  // assumes x is in program memory
  while(pgm_read_byte(x) != 0x00)
    lcd_write_data(pgm_read_byte(x++));
}
 
void lcd_goto_position(uint8_t row, uint8_t col) {
  lcd_set_type_command();
 
  // 20x4 LCD: offsets 0, 0x40, 20, 0x40+20
  uint8_t row_offset = 0;
  switch(row) {
    case 0: row_offset = 0; break;
    case 1: row_offset = 0x40; break;
    case 2: row_offset = 20; break;
    case 3: row_offset = 0x40+20; break;
  }
 
 
  lcd_write_byte(0x80 | (row_offset + col));
}
 
void lcd_line_one()   { lcd_goto_position(0, 0); }
void lcd_line_two()   { lcd_goto_position(1, 0); }
void lcd_line_three() { lcd_goto_position(2, 0); }
void lcd_line_four()  { lcd_goto_position(3, 0); }
 
// lcd_init()
void lcd_init() {
  // set pin driver directions
  // (output on PD7,PD6, and PD3-6)
  DDRD |= 0xfc;
 
  // wait 100msec
  delay_ms(100);
  lcd_set_type_command();
 
  // do reset
  lcd_write_nibble(0x03);
  delay_ms(6);
  lcd_write_nibble(0x03);
  delay_us(250);
  lcd_write_nibble(0x03);
  delay_us(250);
 
  // write 0010 (data length 4 bits)
  lcd_write_nibble(0x02);
  // set to 2 lines, font 5x8
  lcd_write_byte(0x28);
  // disable LCD
  //lcd_write_byte(0x08);
  // enable LCD
  lcd_write_byte(0x0c);
  // clear display
  lcd_write_byte(0x01);
  delay_ms(5);
  // enable LCD
  lcd_write_byte(0x0c);
  // set entry mode
  lcd_write_byte(0x06);
 
  // set cursor/display shift
  lcd_write_byte(0x14);
 
  // clear and home
  lcd_clear_and_home();
}
 
int lcd_putchar(char c, FILE *stream) {
  lcd_write_data(c);
  return 0;
}

Maybe you can use this little tutorial for your Nerdkit Projects.

Just a little hint:
You can only save a Maximum of 8 custom characters in the HD44780 display.
But of course you can overwrite and shift them anytime, so really can use a lot of custom characters and moving animations.

Have fun with your own Pixel Art on your Nerdkit.