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new in LCD
PostPosted: Wed Apr 01, 2009 9:16 pm     Reply with quote
hai All!! can any one help me?

I just try to blink LED and it's OK. Now I try to display Hello World to LCD 16x2. But it's is not ok.

This is my code.

Code:
#include <16F877A.H>
//#include <flex_lcd.c>
#fuses XT, NOWDT, NOPROTECT, BROWNOUT, PUT, NOLVP
#use delay(clock = 2000000)

#include <flex_lcd.c>

//==========================
void main()
{
lcd_init();  // Always call this first.

lcd_putc("\fHello World\n");
lcd_putc("Line Number 2");

while(1);
}



This the flex_lcd driver:

Code:
// flex_lcd.c

// These pins are for the Microchip PicDem2-Plus board,
// which is what I used to test the driver.  Change these
// pins to fit your own board.

#define LCD_DB4   PIN_D0
#define LCD_DB5   PIN_D1
#define LCD_DB6   PIN_D2
#define LCD_DB7   PIN_D3

#define LCD_E     PIN_A1
#define LCD_RS    PIN_A3
#define LCD_RW    PIN_A2

// If you only want a 6-pin interface to your LCD, then
// connect the R/W pin on the LCD to ground, and comment
// out the following line.

#define USE_LCD_RW   1

//========================================

#define lcd_type 2        // 0=5x7, 1=5x10, 2=2 lines
#define lcd_line_two 0x40 // LCD RAM address for the 2nd line


int8 const LCD_INIT_STRING[4] =
{
 0x20 | (lcd_type << 2), // Func set: 4-bit, 2 lines, 5x8 dots
 0xc,                    // Display on
 1,                      // Clear display
 6                       // Increment cursor
 };


//-------------------------------------
void lcd_send_nibble(int8 nibble)
{
// Note:  !! converts an integer expression
// to a boolean (1 or 0).
 output_bit(LCD_DB4, !!(nibble & 1));
 output_bit(LCD_DB5, !!(nibble & 2));
 output_bit(LCD_DB6, !!(nibble & 4));
 output_bit(LCD_DB7, !!(nibble & 8));

 delay_cycles(1);
 output_high(LCD_E);
 delay_us(2);
 output_low(LCD_E);
}

//-----------------------------------
// This sub-routine is only called by lcd_read_byte().
// It's not a stand-alone routine.  For example, the
// R/W signal is set high by lcd_read_byte() before
// this routine is called.

#ifdef USE_LCD_RW
int8 lcd_read_nibble(void)
{
int8 retval;
// Create bit variables so that we can easily set
// individual bits in the retval variable.
#bit retval_0 = retval.0
#bit retval_1 = retval.1
#bit retval_2 = retval.2
#bit retval_3 = retval.3

retval = 0;

output_high(LCD_E);
delay_cycles(1);

retval_0 = input(LCD_DB4);
retval_1 = input(LCD_DB5);
retval_2 = input(LCD_DB6);
retval_3 = input(LCD_DB7);

output_low(LCD_E);

return(retval);
}
#endif

//---------------------------------------
// Read a byte from the LCD and return it.

#ifdef USE_LCD_RW
int8 lcd_read_byte(void)
{
int8 low;
int8 high;

output_high(LCD_RW);
delay_cycles(1);

high = lcd_read_nibble();

low = lcd_read_nibble();

return( (high<<4) | low);
}
#endif

//----------------------------------------
// Send a byte to the LCD.
void lcd_send_byte(int8 address, int8 n)
{
output_low(LCD_RS);

#ifdef USE_LCD_RW
while(bit_test(lcd_read_byte(),7)) ;
#else
delay_us(60);
#endif

if(address)
   output_high(LCD_RS);
else
   output_low(LCD_RS);

 delay_cycles(1);

#ifdef USE_LCD_RW
output_low(LCD_RW);
delay_cycles(1);
#endif

output_low(LCD_E);

lcd_send_nibble(n >> 4);
lcd_send_nibble(n & 0xf);
}

//----------------------------
void lcd_init(void)
{
int8 i;

output_low(LCD_RS);

#ifdef USE_LCD_RW
output_low(LCD_RW);
#endif

output_low(LCD_E);

delay_ms(15);

for(i=0 ;i < 3; i++)
   {
    lcd_send_nibble(0x03);
    delay_ms(5);
   }

lcd_send_nibble(0x02);

for(i=0; i < sizeof(LCD_INIT_STRING); i++)
   {
    lcd_send_byte(0, LCD_INIT_STRING[i]);

    // If the R/W signal is not used, then
    // the busy bit can't be polled.  One of
    // the init commands takes longer than
    // the hard-coded delay of 60 us, so in
    // that case, lets just do a 5 ms delay
    // after all four of them.
    #ifndef USE_LCD_RW
    delay_ms(5);
    #endif
   }

}

//----------------------------

void lcd_gotoxy(int8 x, int8 y)
{
int8 address;

if(y != 1)
   address = lcd_line_two;
else
   address=0;

address += x-1;
lcd_send_byte(0, 0x80 | address);
}

//-----------------------------
void lcd_putc(char c)
{
 switch(c)
   {
    case '\f':
      lcd_send_byte(0,1);
      delay_ms(2);
      break;

    case '\n':
       lcd_gotoxy(1,2);
       break;

    case '\b':
       lcd_send_byte(0,0x10);
       break;

    default:
       lcd_send_byte(1,c);
       break;
   }
}

//------------------------------
#ifdef USE_LCD_RW
char lcd_getc(int8 x, int8 y)
{
char value;

lcd_gotoxy(x,y);

// Wait until busy flag is low.
while(bit_test(lcd_read_byte(),7));

output_high(LCD_RS);
value = lcd_read_byte();
output_low(lcd_RS);

return(value);
}
#endif


My pin connection as below:

LCD_DB4 PIN_D0
LCD_DB5 PIN_D1
LCD_DB6 PIN_D2
LCD_DB7 PIN_D3

LCD_E PIN_A1
LCD_RS PIN_A3
LCD_RW PIN_A2

LCD 5V to 5V 16F877A
LCD Ground to ground 16F877a

Am I need to connect the LCD 5V and Ground to external pin?

my compiler version is 3.214
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Wed Apr 01, 2009 10:14 pm     Reply with quote
Quote:
#use delay(clock = 2000000)

This line is set for 2 MHz. It should probably be 20 MHz.
What is your crystal frequency ?

Quote:
#fuses XT, NOWDT, NOPROTECT, BROWNOUT, PUT, NOLVP

If you do have a 20 MHz crystal, then change the XT fuse to HS.


Also connect the Contrast pin on the LCD to 0.5 volts.
Guest
PostPosted: Thu Apr 02, 2009 6:13 pm     Reply with quote
PCM programmer wrote:
Quote:
#use delay(clock = 2000000)

This line is set for 2 MHz. It should probably be 20 MHz.
What is your crystal frequency ?

Quote:
#fuses XT, NOWDT, NOPROTECT, BROWNOUT, PUT, NOLVP

If you do have a 20 MHz crystal, then change the XT fuse to HS.


Also connect the Contrast pin on the LCD to 0.5 volts.


Thanks PCM_Programmer. Now I succeed to display Hello World. I used 20MHz oscillator. Really happy Very Happy
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