Initalisierung eines LCD Displays

#include <xc888.h>

//Function declarations

void port_init(void);

void delay(int);

void lcdinit(void);

void writecmd(int);

void writedata(char);

void ReturnHome(void);

void wait(unsigned int time);

//*******************

//Pin description

/*

P4.4 to P4.7 is data bus

P4.0 is RS

P4.1 is R/W 

P4.2 is E

*/

//********************

// Defines Pins

sbit RS = 0xC9; // Command or Data

sbit E  = 0xCA; // Enable Port

// R/W dauerhaft auf Masse

// ***********************************************************

// Main program

//

#define P4 P4_DATA

void main(void)

{

   port_init();                                     //Make all ports zero

   lcdinit();                                      //Initilize LCD

   writedata('H');                                 //write

   writedata('e');                                 //write

   writedata('l');                                 //write

   writedata('l');                                 //write

   writedata('o');                                 //write

   ReturnHome();                                   //Return to 0 position      

  while(1)

  {;  

  }

}

void lcdinit(void)

{

  ///////////// Reset process from datasheet /////////

   wait(450);

   P4 &= 0x0F;       // Make P2.4 to P2.7 zero

   P4 |= (0x30&0xF0);    // Write 0x3

   E  = 1;               // => E = 1

   delay(250);

   E  = 0;               // => E = 0

   delay(250);

   P4 &= 0x0F;       // Make P2.4 to P2.7 zero

   P4 |= (0x30&0xF0);    // Write 0x3

   E  = 1;               // => E = 1

   delay(250);

   E  = 0;               // => E = 0

   delay(250);

   delay(300);

   P4 &= 0x0F;       // Make P2.4 to P2.7 zero

   P4 |= (0x30&0xF0);    // Write 0x3

   E  = 1;               // => E = 1

   delay(250);

   E  = 0;               // => E = 0

   delay(250);

     delay(650);

   P4 &= 0x0F;       // Make P2.4 to P2.7 zero

   P4 |= (0x20&0xF0);    // Write 0x2

   E  = 1;               // => E = 1

   delay(250);

   E  = 0;               // => E = 0

   delay(250);

   delay(650);

  /////////////////////////////////////////////////////

   wait (1);

   writecmd(0x28);    //function set

   wait (1);

   writecmd(0x0c);    //display on,cursor off,blink off

   wait (1);

   writecmd(0x01);    //clear display

   wait (3);

   writecmd(0x06);    //entry mode, set increment

   wait (30);

}

void port_init(void)

{

P4_DIR = 0xFF;

PORT_PAGE=1;  

P4_PUDEN=0x00;

P4_PUDSEL=0xFF;  

PORT_PAGE=0;

}

void delay(int a)

{

   int i;

   for(i=0;i<a;i++);

   i=0;

}

void writedata(char t)

{

   RS = 1;             // This is data

   delay(250);

   P4 &= 0x0F;       // Make P2.4 to P2.7 zero

   P4 |= (t&0xF0);  // Write Upper nibble of data

   E  = 1;             // => E = 1

   delay(250);

   E  = 0;             // => E = 0

   delay(250);

   P4 &= 0x0F;       // Make P2.4 to P2.7 zero

   P4 |= ((t<<4)&0xF0);// Write Lower nibble of data

   E  = 1;             // => E = 1

   delay(250);

   E  = 0;             // => E = 0

   delay(250);

}

void writecmd(int z)

{

   RS = 0;             // This is command

   P4 &= 0x0F;       // Make P2.4 to P2.7 zero

   P4 |= (z&0xF0);     // Write Upper nibble of data

   E  = 1;             // => E = 1

   delay(250);

   E  = 0;             // => E = 0

   delay(250);

   P4 &= 0x0F;       // Make P2.4 to P2.7 zero

   P4 |= ((z<<4)&0xF0);// Write Lower nibble of data

   E  = 1;             // => E = 1

   delay(250);

   E  = 0;             // => E = 0

   delay(250);

}

void ReturnHome(void)     //Return to 0 location

{

  writecmd(0x02);

    delay(1500);

}

void wait(unsigned int time)

{

unsigned int zaehler = 0;

TMOD = 1;

TL0 = 0x50;

TH0 = 0xFB;

TCON = 0x10;

while(time != zaehler)

  {

    if(TF0)

    {

      TF0=0;

      TL0=0x20;

      TH0=0xD1; //Reload Wert von 65536-12000 = 53536 => 0xD120 => 1ms timer (12000*83.33 = 999960ns)

      zaehler++;

    }

  }

}