Demo of custom character generation on the Hitachi LCD interface.

cgram.c

/////////////////////////////////////////////////////////////////////////////
// HC12 Program:  I2C Demo
// Processor:     MC9S12XDP512
// Bus Speed:     20 MHz (Requires Active PLL)
// Author:        AJ Armstrong
// Details:       Simple Demo of CGRAM on the Hitachi LCD
// Date:          Dec 2023
// Revision History :
/////////////////////////////////////////////////////////////////////////////

#include <stdio.h>      // For sprintf, etc
#include <ctype.h>      // For character utilities
#include <string.h>     // Various string utilities
#include <hidef.h>      // Common defines and macros
#include "derivative.h" // Derivative-specific definitions
#include "pll.h"        // Phase-locked loop clock control
#include "swled.h"      // GPIO switches and LEDs
#include "segs.h"       // 7-Segment Displays
#include "timer.h"      // Enhanced capture timer
#include "portj.h"      // Interrupt buttons
#include "pit.h"        // Periodic Interrupt timer
#include "rti.h"        // Realtime interrupts
#include "lcd.h"        // LCD Display
#include "sci.h"        // Serial communications interface (EIA/TIA-232)
#include "i2c.h"        // Carlos Estay's I2C Driver Libraries

/////////////////////////////////////////////////////////////////////////////
// Constants
/////////////////////////////////////////////////////////////////////////////

// A couple of Custom characters. Note format: an array of 8 bytes with three
// leading zeroes and then a five bit row with zeros for off pixels and 1 for
// on.  By convention, the last row is left blank to permit showing the cursor.
const char cgSmiley[] =  //Happy face
{
  0b00000000, //... .....
  0b00000000, //... .....
  0b00010001, //... *...*
  0b00000000, //... .....
  0b00000000, //... .....
  0b00010001, //... *...*
  0b00001110, //... .***.
  0b00000000, //... .....
};

const char cgFrowny[] = //Sad face
{
  0b00000000, //... .....
  0b00000000, //... .....
  0b00010001, //... *...*
  0b00000000, //... .....
  0b00000000, //... .....
  0b00001110, //... .***.
  0b00010001, //... *...*
  0b00000000, //... .....
};

/////////////////////////////////////////////////////////////////////////////
// Main Entry
/////////////////////////////////////////////////////////////////////////////

void main(void)
{
  // Variables
  int i = 0; // Loop counter

  /////////////////////////////////////////////////////////////////////////////
  // One-Time Initializations
  /////////////////////////////////////////////////////////////////////////////
  _DISABLE_COP();        // No watchdog
  PLL_To20MHz();                         // Configure the main clock to 20 MHz (implications for timers)
  SWL_Init();                            // Standard initialization for switches and LEDs
  SEG_Init();                            // Standard initializaton for 7-seg displays
  RTI_Init();                            // Initialize RTI timer

  /////////////////////////////////////////////////////////////////////////////
  // Setup
  /////////////////////////////////////////////////////////////////////////////

  EnableInterrupts; // Ensure our board will respond to interrupt signals.
  LCD_Init(); // My current LCD drivers need RTI and interrupts. //FIXME
  LCD_StringRC(0,5,"CGRAM Demo"); //Top line, centered
  LCD_StringRC(1,5,"----------"); //Second line, centered

  // DDRAM is the display memory: each location corresponds to a character
  // on the display.  CGRAM is 64 bytes divided up into 8 8-byte blocks---
  // each block corresponding to a special character that can be displayed
  // as special characters with ASCII values 0 through 7.  The two arrays of
  // bytes above show the format needed to define the character.

  // First, we set our address to location 0 in CGRAM
  LCD_Inst(0b01000000); //Set CGRAM command - 0x0100 0xxx where xxx are addresses 0-7
  
  // Now, iterate through my array of rows and write all 8 to the device:
  for (i = 0 ; i < 8 ; ++i)
    LCD_Data(cgSmiley[i]);

  // My custom smiley character will now be printed if I send a zero as my character
  // at any location in DDRAM.

  // After I used the above code to develop CGRAM support in my library, 
  // I can simplify this into the below for creating a frowny face.
  LCD_CGChar(1,cgFrowny); // Special character will be at ASCII 0x01

  //Show them on the LCD
  LCD_AddrRC(2,10); // Third line, middle
  LCD_Data(0); //Special character 0 is smiley(ASCII 0, not '0')

  //Show them on the LCD
  LCD_AddrRC(3,10); // Fourth line, middle
  LCD_Data(1); //Special character 1 is frowny (ASCII 1, not '1')

  /////////////////////////////////////////////////////////////////////////////
  // Main Program Loop
  /////////////////////////////////////////////////////////////////////////////

  for (;;)
  {
    asm WAI; //Wait for something interesting to happen
  }
}