/*
 *	LCD interface example
 *	Uses routines from delay.c
 *	This code will interface to a standard LCD controller
 *	like the Hitachi HD44780. It uses it in 4 bit mode, with
 *	the hardware connected as follows (the standard 14 pin 
 *	LCD connector is used):
 *	
 *	PORTB bits 0-3 are connected to the LCD data bits 4-7 (high nibble)
 *	PORTA bit 2 is connected to the LCD RS input (register select)
 *	PORTA bit 3 is connected to the LCD EN bit (enable)
 *	
 *	To use these routines, set up the port I/O (TRISA, TRISB) then
 *	call lcd_init(), then other routines as required.
 *
 * Copywrite Craig Lee 1998
 *	
 */

#include	<pic.h>
#include	"lcd.h"
#include	"delay.h"

#define LCD_RS	RA5	// Register select
#define LCD_EN	RB4	// Enable
#define LCD_D4 RB5	// Data bits
#define LCD_D5 RC5	// Data bits
#define LCD_D6 RC4	// Data bits
#define LCD_D7 RC3	// Data bits

#define	LCD_STROBE	((LCD_EN = 1),(LCD_EN=0))


/* write a byte to the LCD in 4 bit mode */

void
lcd_write(unsigned char c)
{
	if(c & 0x80) LCD_D7=1; else LCD_D7=0;
	if(c & 0x40) LCD_D6=1; else LCD_D6=0;
	if(c & 0x20) LCD_D5=1; else LCD_D5=0;
	if(c & 0x10) LCD_D4=1; else LCD_D4=0;
	LCD_STROBE;
	if(c & 0x08) LCD_D7=1; else LCD_D7=0;
	if(c & 0x04) LCD_D6=1; else LCD_D6=0;
	if(c & 0x02) LCD_D5=1; else LCD_D5=0;
	if(c & 0x01) LCD_D4=1; else LCD_D4=0;
	LCD_STROBE;	
	DelayUs(40);
}

/*
 * 	Clear and home the LCD
 */

void
lcd_clear(void)
{
	LCD_RS = 0;

	lcd_write(0x1);
	DelayMs(2);
}

/* write a string of chars to the LCD */

void
lcd_puts(const char * s)
{
	LCD_RS = 1;	// write characters

	while(*s) lcd_write(*s++);
}

/* write one character to the LCD */

void
lcd_putch(unsigned char c)
{
	LCD_RS = 1;	// write characters

	lcd_write(c);
}


/*
 * Go to the specified position
 */

void
lcd_goto(unsigned char pos)
{
	LCD_RS = 0;

	lcd_write(0x80 + pos);
}
	
/* initialise the LCD - put into 4 bit mode */

void
lcd_init(void)
{
	LCD_RS = 0;	// write control bytes

	DelayMs(15);// power on delay

	LCD_D4 = 1;	// init!	
	LCD_D5 = 1; //
	LCD_STROBE;	
	DelayMs(5);

	LCD_STROBE;	// init!	
	DelayUs(100);

	LCD_STROBE;	// init!	
	DelayMs(5);

	LCD_D4 = 0;	// set 4 bit mode
	LCD_STROBE;	
	DelayUs(40);
	
	lcd_write(0x28);// 4 bit mode, 1/16 duty, 5x8 font, 2lines
	lcd_write(0x0C);// display on
	lcd_write(0x06);// entry mode advance cursor
	lcd_write(0x01);// clear display and reset cursor
}

Questions:

• KILLspamnickomalleySPAM at TakeThisOuTntlworld.com asks:

  Hello, Has anyone had experience with driving a Laptop LCD display, I have a one from an old laptop as was wondering if a PIC could be used to drive it, It is a panasonic cf27 laptop and the dispaly is a standard 640x480 lcd, any ideas and or source code would be very appreciated. Best regards Nick

Code:

• Colin D Barnard shares this code:

  
   
  //**Project Name: VFD
  //**File Name   : vfd0_3.c
  //**Version     : 0.3
  //**Date        : 24/02/2002	
  //**Revision	: 28/02/2002 added bit swap routine
  //**		: 02/03/2002 fixed error in display routine and added delay to
  //**		: 	     WR_PIN strobe.
  //**		:	
  //**		
  //**Processor	:16F84/628
  //**
  //** Copyright CDB.  email bodgy1@optusnet.com.au
  
  // Program to display data on a Futoba M202SD08GL vacuum fluorescent display.
  // Using parallel mode. Data is on port B and control on port A.
  // Connections as follows
  //
  // Display Pins. 1 3 5 7 9 11 13 15
  //    Data Bits. 7 6 5 4 3 2  1  0
  //
  // Control Pins.  20   18  17  16   8
  //  Signal Name. Busy  SEL WR TEST RST
  //
  // Pins 2 4 6 +5v; 10 12 14 Gnd
  
  // Pic Pins    B7 B6 B5 B4 B3 B2 B1 B0
  //	       D0 D1 D2 D3 D4 D5 D6 D7
  //
  // PortA       A0  A1  A2   A3  A4
  //             WR SEL TEST RST BUSY
  // A0-A3 output A4 input.
  //
  // WR, SEL active low. data latched on WR 0->1; RST must be momentarily grounded 
  // at start up to activate display.
  
  #define F628
  #ifdef F628
    #include <P16F628.h>
  #else	
   #include <P16F84.h>
  #endif
  
  #include "uS_delay.c"
  
  	
  #define CONTROL_PORT PORTA
  #define DATA_PORT    PORTB
  #define WR_PIN  PA.B0
  #define SEL_PIN PA.B1
  #define TEST_PIN PA.B2
  #define RST_PIN PA.B3
  #define BUSY_PIN PA.B4
  #define HIGH 1
  #define LOW 0
  #define STROBE (PORTA^=1)
  #define MAX_ROW 20
  #define LINES 2
  
  // VFD Control Commands
  #define LF 0x0A		//Line Feed
  #define CR 0x0D		//Carriage Return
  #define CUROFF 0x14	//DC4
  #define CURON  0x13	//DC3
  #define DIMM 0x04	//Dimming uses vfd_command
  #define DIM2 0x20	//Dimm 20%
  #define DIM4 0x40	//Dimm 40%
  #define DIM8 0x80	//Dimm 80%
  #define DIMF 0xFF	//Dimm 100%
  #define VTS  0x12	//DC2 Mode
  #define NORM 0x11	//DC1 Mode
  #define HTS  0x09	//Tab right  one space
  #define BSP  0x09	//Backspace
  #define DP   0x10	//Display position  uses vfd_command
  #define RST  0x1F	//Soft reset
  
  #ifdef F628
     # __config 0x3F61	//16F628  fuse 
  #else
     # __config 0x3FF1	//16F84(a) fuse
  #endif
  
  
  //Prototypes 
  		
  void main();	
  void setup();
  void reset_vfd();
  void test_vfd();
  void vfd_display(unsigned char *disp_string);
  void vfd_out(unsigned char *text);
  void vfd_ch(unsigned char ch);
  void vfd_command(unsigned char com, unsigned char action);
  void vfd_position(unsigned char line,unsigned char pos);
  
  void main()
  {
    
   setup();
   big_delay(10);		//settling time
   reset_vfd();		//Hard reset
   test_vfd();		//Run inbuilt test routine
   SEL_PIN=LOW;		//Enable display for data
   big_delay(10);
   
   vfd_ch(CUROFF);
   vfd_display("Futoba VFD Display");
   big_delay(3000);
   vfd_command(LF,CR);
   vfd_display("Dimming 20%");
   vfd_command(DIMM,DIM2); 		//20% brightness
   big_delay(5000);
   vfd_command(DIMM,DIMF);	       //Full brightness
   vfd_ch(RST);			      // Clear display	
   vfd_ch(CUROFF);
   vfd_command(CR,LF);
   vfd_display("pos");
   vfd_position(2,5);
   vfd_display("2,5");
   big_delay(5000);
   vfd_ch(VTS);
   vfd_display(" vertical tab");
   big_delay(5000);
   vfd_ch(RST);
   vfd_ch(CUROFF);
   vfd_display("Futoba VFD Display");
   vfd_position(2,5);
   vfd_display("End of Demo");
   vfd_command(DIMM,DIM4);	//40% brightness	
   
   while(1)
   {
   }				//forever!
  }
  
  // cmcon=(1<<CM2) |(1<<CM1) |(1<<CM0) void setup() { #ifdef F628 CMCON=0x07; // switch comparators off #endif CONTROL_PORT=0x0E; // RST=1 TEST=1 SEL=1 WR=0 DATA_PORT=0; TRISA=0x10; //PortA A4=in a4:a0 out TRISB=0x00; } void reset_vfd() { RST_PIN=LOW; //Take reset pin low to awake VFD small_delay(1); //12 microsecond settling time RST_PIN=HIGH; //Return reset pin to operating state } void test_vfd() { TEST_PIN=LOW; big_delay(28000); // delay 20 seconds approx TEST_PIN=HIGH; } void vfd_display(unsigned char *string) { while(*string) //while not end of string { vfd_out(string); *string++; //move to next character } } // Following routine only required due to pin out chosen. This was chosen from // a PCB perspective. // // D7 D6 D5 D4 D3 D2 D1 D0 -> D0 D1 D2 D3 D4 D5 D6 D7
  //
  // Using the extra variable 'original1' saves 3 program words
  
  unsigned char buffer,original;
  
  void vfd_out(unsigned char *text)
  {
     const unsigned char table[16]=      
     {0x00, 0x08, 0x04, 0x0C, 0x02, 0x0A, 0x06, 0x0E,
     
      0x01, 0x09, 0x05, 0x0D, 0x03, 0x0B, 0x07,0x0F};
      
      unsigned char original1;
          
      original=*text;
      original1=original & 0x0f;	// Mask off lower nibble
      buffer=table[original1];	//look up conversion pattern lower nibble
      #asmline swapf buffer,f	;swap places make it high nibble
      #asmline swapf original,f   ;swap original byte around
      original&=0x0f;
      buffer|=table[original];    //look up pattern for new lower nibble
      				//IOR with current contents
      DATA_PORT=buffer;		//Bung it on to PORTB
      while (BUSY_PIN)
      {
      }
      STROBE;		//Clock the data into the VFD
      small_delay(30);   //100 microseconds
      STROBE;	       //Return pin low	
  
  }
  
  void vfd_ch(unsigned char ch)
  {
    unsigned char *text;
    
    text=&ch;
    vfd_out(text);
    
  }
  
  void vfd_command(unsigned char com, unsigned char action)
  {
    vfd_ch(com);
    vfd_ch(action);
  }
  
  void vfd_position(unsigned char line,unsigned char pos)
  {
    
      if (line==LINES)
      {
        pos+=(MAX_ROW-1);
      } 
      else
      {
        pos=-1;
      }     
      vfd_command(DP,pos);
   
    
  }
  

• Code for a vacuum flourescent display in C
  
  
  //**Project Name: VFD
  //**File Name   : vfd0_3.c
  //**Version     : 0.3
  //**Date        : 24/02/2002	
  //**Revision	: 28/02/2002 added bit swap routine
  //**		: 02/03/2002 fixed error in display routine and added delay to
  //**		: 	     WR_PIN strobe.
  //**		:	
  //**		
  //**Processor	:16F84/628
  //**
  //** Copyright CDB.  email bodgy1@optusnet.com.au
  
  // Program to display data on a Futoba M202SD08GL vacuum fluorescent display.
  // Using parallel mode. Data is on port B and control on port A.
  // Connections as follows
  //
  // Display Pins. 1 3 5 7 9 11 13 15
  //    Data Bits. 7 6 5 4 3 2  1  0
  //
  // Control Pins.  20   18  17  16   8
  //  Signal Name. Busy  SEL WR TEST RST
  //
  // Pins 2 4 6 +5v; 10 12 14 Gnd
  
  // Pic Pins    B7 B6 B5 B4 B3 B2 B1 B0
  //	       D0 D1 D2 D3 D4 D5 D6 D7
  //
  // PortA       A0  A1  A2   A3  A4
  //             WR SEL TEST RST BUSY
  // A0-A3 output A4 input.
  //
  // WR, SEL active low. data latched on WR 0->1; RST must be momentarily grounded 
  // at start up to activate display.
  
  #define F628
  #ifdef F628
    #include <P16F628.h>
  #else	
   #include <P16F84.h>
  #endif
  
  #include "uS_delay.c"
  
  	
  #define CONTROL_PORT PORTA
  #define DATA_PORT    PORTB
  #define WR_PIN  PA.B0
  #define SEL_PIN PA.B1
  #define TEST_PIN PA.B2
  #define RST_PIN PA.B3
  #define BUSY_PIN PA.B4
  #define HIGH 1
  #define LOW 0
  #define STROBE (PORTA^=1)
  #define MAX_ROW 20
  #define LINES 2
  
  // VFD Control Commands
  #define LF 0x0A		//Line Feed
  #define CR 0x0D		//Carriage Return
  #define CUROFF 0x14	//DC4
  #define CURON  0x13	//DC3
  #define DIMM 0x04	//Dimming uses vfd_command
  #define DIM2 0x20	//Dimm 20%
  #define DIM4 0x40	//Dimm 40%
  #define DIM8 0x80	//Dimm 80%
  #define DIMF 0xFF	//Dimm 100%
  #define VTS  0x12	//DC2 Mode
  #define NORM 0x11	//DC1 Mode
  #define HTS  0x09	//Tab right  one space
  #define BSP  0x09	//Backspace
  #define DP   0x10	//Display position  uses vfd_command
  #define RST  0x1F	//Soft reset
  
  #ifdef F628
     # __config 0x3F61	//16F628  fuse 
  #else
     # __config 0x3FF1	//16F84(a) fuse
  #endif
  
  
  //Prototypes 
  		
  void main();	
  void setup();
  void reset_vfd();
  void test_vfd();
  void vfd_display(unsigned char *disp_string);
  void vfd_out(unsigned char *text);
  void vfd_ch(unsigned char ch);
  void vfd_command(unsigned char com, unsigned char action);
  void vfd_position(unsigned char line,unsigned char pos);
  
  void main()
  {
    
   setup();
   big_delay(10);		//settling time
   reset_vfd();		//Hard reset
   test_vfd();		//Run inbuilt test routine
   SEL_PIN=LOW;		//Enable display for data
   big_delay(10);
   
   vfd_ch(CUROFF);
   vfd_display("Futoba VFD Display");
   big_delay(3000);
   vfd_command(LF,CR);
   vfd_display("Dimming 20%");
   vfd_command(DIMM,DIM2); 		//20% brightness
   big_delay(5000);
   vfd_command(DIMM,DIMF);	       //Full brightness
   vfd_ch(RST);			      // Clear display	
   vfd_ch(CUROFF);
   vfd_command(CR,LF);
   vfd_display("pos");
   vfd_position(2,5);
   vfd_display("2,5");
   big_delay(5000);
   vfd_ch(VTS);
   vfd_display(" vertical tab");
   big_delay(5000);
   vfd_ch(RST);
   vfd_ch(CUROFF);
   vfd_display("Futoba VFD Display");
   vfd_position(2,5);
   vfd_display("End of Demo");
   vfd_command(DIMM,DIM4);	//40% brightness	
   
   while(1)
   {
   }				//forever!
  }
  
  // cmcon=(1<<CM2) |(1<<CM1) |(1<<CM0) void setup() { #ifdef F628 CMCON=0x07; // switch comparators off #endif CONTROL_PORT=0x0E; // RST=1 TEST=1 SEL=1 WR=0 DATA_PORT=0; TRISA=0x10; //PortA A4=in a4:a0 out TRISB=0x00; } void reset_vfd() { RST_PIN=LOW; //Take reset pin low to awake VFD small_delay(1); //12 microsecond settling time RST_PIN=HIGH; //Return reset pin to operating state } void test_vfd() { TEST_PIN=LOW; big_delay(28000); // delay 20 seconds approx TEST_PIN=HIGH; } void vfd_display(unsigned char *string) { while(*string) //while not end of string { vfd_out(string); *string++; //move to next character } } // Following routine only required due to pin out chosen. This was chosen from // a PCB perspective. // // D7 D6 D5 D4 D3 D2 D1 D0 -> D0 D1 D2 D3 D4 D5 D6 D7
  //
  // Using the extra variable 'original1' saves 3 program words
  
  unsigned char buffer,original;
  
  void vfd_out(unsigned char *text)
  {
     const unsigned char table[16]=      
     {0x00, 0x08, 0x04, 0x0C, 0x02, 0x0A, 0x06, 0x0E,
     
      0x01, 0x09, 0x05, 0x0D, 0x03, 0x0B, 0x07,0x0F};
      
      unsigned char original1;
          
      original=*text;
      original1=original & 0x0f;	// Mask off lower nibble
      buffer=table[original1];	//look up conversion pattern lower nibble
      #asmline swapf buffer,f	;swap places make it high nibble
      #asmline swapf original,f   ;swap original byte around
      original&=0x0f;
      buffer|=table[original];    //look up pattern for new lower nibble
      				//IOR with current contents
      DATA_PORT=buffer;		//Bung it on to PORTB
      while (BUSY_PIN)
      {
      }
      STROBE;		//Clock the data into the VFD
      small_delay(30);   //100 microseconds
      STROBE;	       //Return pin low	
  
  }
  
  void vfd_ch(unsigned char ch)
  {
    unsigned char *text;
    
    text=&ch;
    vfd_out(text);
    
  }
  
  void vfd_command(unsigned char com, unsigned char action)
  {
    vfd_ch(com);
    vfd_ch(action);
  }
  
  void vfd_position(unsigned char line,unsigned char pos)
  {
    
      if (line==LINES)
      {
        pos+=(MAX_ROW-1);
      } 
      else
      {
        pos=-1;
      }     
      vfd_command(DP,pos);
   
    
  }
  
  

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