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Display Strings on LCD Screen
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mcad



Joined: 25 Nov 2007
Posts: 48

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Display Strings on LCD Screen
PostPosted: Mon Nov 26, 2007 1:56 pm     Reply with quote

Hi All,
I wan to display a string on the LCD Screen. For this, I used the lcd_putc() function, but there is nothing appeared on the screen.
So, would you please explain me why ?
And would you please suggest me any alternative function to display strings on the LCD Screen ?

Thanks,
Regards
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Mon Nov 26, 2007 2:07 pm     Reply with quote

Quote:

I want to display a string on the LCD Screen. For this, I used the
lcd_putc() function, but there is nothing appeared on the screen.

Post a small test program that shows how are trying to use lcd_putc()
to display a string.

Example of a small test program:
http://www.ccsinfo.com/forum/viewtopic.php?t=25994&start=3
mcad



Joined: 25 Nov 2007
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PostPosted: Mon Nov 26, 2007 2:17 pm     Reply with quote

My code is as the following, sir.

Code:
taken back for a while


Last edited by mcad on Mon Nov 26, 2007 5:54 pm; edited 1 time in total
PCM programmer



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PostPosted: Mon Nov 26, 2007 2:47 pm     Reply with quote

You don't have a #fuses statement. You should always have one.
Add one, as shown below, and try it again.

Code:
#include <16F877.h>
#fuses XT, NOWDT, NOPROTECT, BROWNOUT, PUT, NOLVP
#use delay(clock=4000000)

#define use_portb_lcd TRUE
#include <LCD.C>
mcad



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PostPosted: Mon Nov 26, 2007 3:08 pm     Reply with quote

Is the only problem derived from fuse derictive, sir ?
PCM programmer



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PostPosted: Mon Nov 26, 2007 3:21 pm     Reply with quote

Always show a complete test program. For example, if you are missing
the "NOLVP" fuse, the PIC can lock-up. Nothing will work.
mcad



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PostPosted: Mon Nov 26, 2007 3:36 pm     Reply with quote

Sir, I mean can I use the lcd_putc with strings ?
It seems that it is only used with chars.
PCM programmer



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PostPosted: Mon Nov 26, 2007 3:45 pm     Reply with quote

Did you see my example program ? Of course you can use it with strings.
However, they are constant strings.

If you want to display a string that is stored in a RAM array, then
use the re-direction feature of printf() in CCS. You can send the
output of the printf() function to the lcd_putc() function. See this
post for an example:
http://www.ccsinfo.com/forum/viewtopic.php?t=20286&start=3
mcad



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PostPosted: Mon Nov 26, 2007 3:47 pm     Reply with quote

Ok, sir
Thanks a lot again.

Best wishes

Regards
mcad



Joined: 25 Nov 2007
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PostPosted: Wed Nov 28, 2007 1:56 am     Reply with quote

Hi sir,
I heard that printf( ) will output its string via the rs232 port. So, I wonder that without using serial port, can we use printf function ?

Thanks
mcad



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PostPosted: Wed Nov 28, 2007 3:41 am     Reply with quote

Hi all,
I am now trying to execute the followng code. But it does not display anything on the lcd screen.

Would anyone please help me ?

Code:

taken back for a while


Last edited by mcad on Thu Nov 29, 2007 6:46 am; edited 1 time in total
Audi80



Joined: 07 Sep 2007
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PostPosted: Wed Nov 28, 2007 4:51 am     Reply with quote

Hi there mcad use this example with flexy_lcd.c its working!!! Cool
Don´t forget to check the lcd control pins they are described in the lcd driver.
Code:
#include <16F876A.h>
#fuses HS,NOWDT,NOPROTECT,NOLVP
#use delay(clock=20000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7)
#include <flexy_lcd.c>
#include <stdio.h>
//////////////////////////////////////////////
char cartao[10];
int a=0;
char aux;
//////////////////////////////////////////////
void escreve_no_lcd();
//////////////////////////////////////////////

#int_rda
void serial_isr() {

   output_high(PIN_B3);
   aux=getc();
   if(aux=='0'||aux=='1'||aux=='2'||aux=='3'||aux=='4'||aux=='5'||aux=='6'||aux=='7'||aux=='8'||aux=='9'){
   cartao[a]=aux;
   ++a;
   }
   if(a==10){
      a=0;
      escreve_no_lcd();
   }
   delay_ms(400);
   output_low(PIN_B3);

}




void main() {


   lcd_init();
   lcd_putc("\fPasse o cartão!!!\n");
   enable_interrupts(global);
   enable_interrupts(int_rda);
   while(true);
}


void escreve_no_lcd(){
   int i;
   for(i=0;i<strlen(cartao);++i){
      lcd_putc(cartao[i]);
   }
   lcd_putc('\n');
}


And the 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_B4
#define LCD_DB5   PIN_B5
#define LCD_DB6   PIN_B6
#define LCD_DB7   PIN_B7

#define LCD_E     PIN_B2
#define LCD_RS    PIN_B1
//#define LCD_RW    PIN_B3

// 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


Don´t forget to check your lcd contrast too it may be to light and you can´t see anything. Keep on the good work Wink
mcad



Joined: 25 Nov 2007
Posts: 48

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PostPosted: Wed Nov 28, 2007 5:10 am     Reply with quote

Thank you for this,
but I especially want to see where I am making mistakes.
Would any one please help me ?
When I used the above code, there is no any action occured in the boards and the LCD but also there is no any error occured in the program.
I got crazy and stop working on it. Now, I am waiting anyone who can help me on this.

Thanks
Audi80



Joined: 07 Sep 2007
Posts: 41

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PostPosted: Wed Nov 28, 2007 5:33 am     Reply with quote

There can be many mistakes. i.e. if you only change one control pin of the lcd it will not work if your lcd contrast is to low you think that is not working but it is the only thing is that you cant see it. There may be other problems like your LCD may not be properly connected with vcc and gnd or the A-K connection. Check everything first...
mcad



Joined: 25 Nov 2007
Posts: 48

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PostPosted: Wed Nov 28, 2007 1:12 pm     Reply with quote

Any other suggestions ?
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