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Half display on LCD with flex_lcd.c

 
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noral



Joined: 09 May 2014
Posts: 4

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Half display on LCD with flex_lcd.c
PostPosted: Tue May 13, 2014 6:41 pm     Reply with quote

Hi everyone!

I have a problem with the LCD. I've got a Hitachi LM016L 16x2 with a PIC24FJ128GC010. I'm using CCS compiler and the flex_lcd.c driver.

When I try to show a message in the LCD, I can only see half message (only the first 8 characters of each line).

Can anyone help me? Embarassed

I share with you my "Hello World" code and the flex_lcd.c code.

Thanks in advance.

main code:
Code:
#include <24FJ128GC010.H>
#fuses FRC, NOWDT, NOPROTECT, BROWNOUT, ICSP1
#use delay(clock = 8000000)
#include <flex_lcd.c>

//==========================
void main()
{


lcd_init();
delay_ms(1000);
printf(lcd_putc,"\fHello World\n");
lcd_putc("Hola Mundo");

while(1);
}




flex_lcd.c code:

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
temtronic



Joined: 01 Jul 2010
Posts: 9243
Location: Greensville,Ontario

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PostPosted: Tue May 13, 2014 7:43 pm     Reply with quote

one comment...
please put a

delay_ms(500);

before the lcd_init();

You need to give the LCD module time to 'get organized' before you try to access it.

Some modules need less time, a couple more, but 500ms has always worked for me..

The flex driver has been reliable for several displays.

recode/recompile/retest, report back what happens.


hth
jay
notbad



Joined: 10 Jan 2013
Posts: 68

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PostPosted: Wed May 14, 2014 1:12 am     Reply with quote

There is a similar problem with some 16x1 LCDs. Maybe it has something to do with that.
Some 16x1 LCDs have to be configured as 8x2. Take a look at PCM_Programmer's driver for 16x1 LCDs (flex_lcd_16x1.c).

Hope that helps. Smile
noral



Joined: 09 May 2014
Posts: 4

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PostPosted: Wed May 14, 2014 2:19 am     Reply with quote

temtronic wrote:
one comment...
please put a

delay_ms(500);

before the lcd_init();

You need to give the LCD module time to 'get organized' before you try to access it.

Some modules need less time, a couple more, but 500ms has always worked for me..

The flex driver has been reliable for several displays.

recode/recompile/retest, report back what happens.


hth
jay


Thanks for your reply Jay Smile

I've retested with this delay before the lcd_init(); but keep showing half screen.

I've tried with 1000ms and 500ms unsuccessfully :(
Ttelmah



Joined: 11 Mar 2010
Posts: 19540

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PostPosted: Wed May 14, 2014 4:18 am     Reply with quote

Unfortunately, the best thing to do, would be to start testing with a quick test with a second display!....

The LCD you have uses one of the most 'standard' chipsets (it was the ancestor, that was copied by many others), and should work directly with the flex_lcd driver. However the first question would be 'are you seeing the correct characters in the half of the screen that does display?. If not, you could have one data line not connecting properly.

Then there are two variants of the chip used on different displays. The newer 44780S which directly supports 16*2, and the older 44780U which only directly supports 8*2, until a second expansion chip is added. You might have this second variant, with a faulty expansion chip...

On the different 16*1 version mentioned by 'notbad', some of the 16*1 displays are actually wired internally as an 8*2, and these then need the 8*2 driver. This can't directly apply to the 16*2.
temtronic



Joined: 01 Jul 2010
Posts: 9243
Location: Greensville,Ontario

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PostPosted: Wed May 14, 2014 4:44 pm     Reply with quote

Another test you could make on the display you have is to run in in native 8 bit mode. It requires a few more wires(4) but you could then confirm the display does function. Since 1/2 the display doesn't in 4 bit mode it could be a hardware problem and not the driver.

hth
jay
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