[SOLVED] LCD 4 bit Mode is not working

[thannara123]

I am trying to make an LCD Interfacing with 4 bit mode ,
But not working I tried a lot of
Data looked in Debug mode good not found wrong

what is the problem ?

Attached Code and Proteus files

#pragma config FOSC = XT        // Oscillator Selection bits (XT oscillator)
#pragma config WDTE = OFF       // Watchdog Timer Enable bit (WDT disabled)
#pragma config PWRTE = OFF      // Power-up Timer Enable bit (PWRT disabled)
#pragma config BOREN = OFF      // Brown-out Reset Enable bit (BOR disabled)
#pragma config LVP = ON         // Low-Voltage (Single-Supply) In-Circuit Serial Programming Enable bit (RB3/PGM pin has PGM function; low-voltage programming enabled)
#pragma config CPD = OFF        // Data EEPROM Memory Code Protection bit (Data EEPROM code protection off)
#pragma config WRT = OFF        // Flash Program Memory Write Enable bits (Write protection off; all program memory may be written to by EECON control)
#pragma config CP = OFF         // Flash Program Memory Code Protection bit (Code protection off)

#define _XTAL_FREQ 1000000

#include <xc.h>
#define LCD_PORTB PORTB
#define RS  RB0
#define EN  RB1

void Strobe (void)
{
    EN = 1;
    __delay_us(1);
     EN = 0;
 
}
void LCD_cmd( unsigned char cmd)
{
    RS = 0;
    __delay_ms(1);
    LCD_PORTB = (cmd & 0xf0) ;
    Strobe();
    LCD_PORTB = (cmd << 4 );
    Strobe();
}
void LCD_data( unsigned char data)
{
     RS = 1;
    __delay_ms(1);
    LCD_PORTB |= (data & 0xf0);
    Strobe();
    LCD_PORTB |= (data << 4 );
    Strobe();
}
void LCD_init()
{
    __delay_ms(20);
     LCD_cmd(0x38);
     __delay_ms(4);
     LCD_cmd(0x38);
    __delay_ms(10);
   // LCD_cmd(0x38);   // Power on Initilization
    LCD_cmd(0x28);    /* 4bit mode */
    LCD_cmd(0x28);    /* Initialization of 16X2 LCD in 4bit mode */
 
    LCD_cmd(0x0C);    /* Display ON Cursor OFF */
    LCD_cmd(0x06);    /* Auto Increment cursor */
 
}
void string(const char *ptr)
{
    while (*ptr)
    {
        LCD_data(*ptr++);
    }
}

     void main()
    {
       TRISB =0;
       TRISD =0;
   
   
       LCD_init();
       LCD_cmd(0x80);
     //string("HELLO WORLD");
      // LINE2;
       string("IT IS WORKING:-)");
   
       while(1);
        return ;
}

 

[andre_luis]

Did you even check connections ? Don't seem clear the missing crossing dot at the VSS bus of LCD module ?

 

[thannara123]

i didnt changed the circuit connection and re uploded the picture

 

[andre_luis]

What should one figure out from the above picture ? Are you considering that removing the whole wire from the VSS pin at the LCD module would solve the missing net connection ?

--- Updated Jan 11, 2023 ---

In addition, got rid of the VEE biasing connection; I guess it should not be feft floating.

 

[thannara123]

What should one figure out from the above picture ? Are you considering that removing the whole wire from the VSS pin at the LCD module would solve the missing net connection ?

--- Updated Jan 11, 2023 ---

In addition, got rid of the VEE biasing connection; I guess it should not be feft floating.

Sir ,
In proteus simulation its worked yet it not conected , i already connected it earlier the above picture it is removed (sorry )

 

[danadakk]

Vee controls contrast and needs to be adjustable ( use a 5 or 10K pot):

Does your code check the LCD busy state ?

Regards, Dana.

 

[betwixt]

Try clearing PORTB before writing data to it. Just ORing new bits doesn't mean only those bits are set.

Brian.

 

[Aussie Susan]

In proteus simulation its worked .......

Are you using real hardware or a simulator?
Also what is not working? If it is simply no characters visible, then try setting up the 'contrast' voltage and turning it so that you see the blank rectangles and then turn it back a little (until the rectangles are very faint or just not visible). A common mistake is to have the contract set so low that the character 'dots' are not lit up.

Also @danadakk: the wiring around the variable resistor is wrong - no connection to Vss.
Susan

 

[danadakk]

Are you using real hardware or a simulator?
Also what is not working? If it is simply no characters visible, then try setting up the 'contrast' voltage and turning it so that you see the blank rectangles and then turn it back a little (until the rectangles are very faint or just not visible). A common mistake is to have the contract set so low that the character 'dots' are not lit up.

Also @danadakk: the wiring around the variable resistor is wrong - no connection to Vss.
Susan

The pot V wants to range from Vss to Vdd, at least thats what I am doing on my baords and works just fine to
control the contrast. Seems like most of the time Vee in a 5V system wants to be ~ 3 to 4 V.


Regards, Dana.

 

[thannara123]

@[B]danadakk[/B] , My code is not checking Busy Flag of LCD

@betwixt , where does the port clear inside the Functions ? (tried inside the function by initlizing with zero but not worked )​

@Aussie Susan I am Simulating on proteus ,Thats y i didnt connected Vss and VEE, in my previous simulation ,its works without VDD and VEE ,
Now in this simulation i tried VEE to VCC and VSS to GND ,But not worked .
Nothing displyaing the LCD



Is my code okay ?

 

[FvM]

@betwixt , where does the port clear inside the Functions ? (tried inside the function by initlizing with zero but not worked )

Did you understand why |= can't work in this place? I wonder how you arrived at this code? Did you invent it on your own, or is it copy-and-paste fault?

 

[thannara123]

Did you understand why |= can't work in this place? I wonder how you arrived at this code? Did you invent it on your own, or is it copy-and-paste fault?

Sir Nothing done there by ORing i too much time tired by rediting the code so ,i forget to remove that OR operator .

Earlier i done and worked a lot of LCD interface .

For a long time I cant do electronics .After 4,5 years i am refreshing my some of ,

I tired this circuit and the code is by changing several time to work out .

RS = 0;   
    __delay_ms(1);    
    LCD_PORTB = (cmd & 0xf0) ;  
    Strobe();
    LCD_PORTB = (cmd << 4 );
    Strobe();

I think this code is enogh isnt it sir ? , But not working

 

[FvM]

You should try to understand what you are doing here.

RS is also located in PORTB, so the correct LCD_DATA function could like this

void LCD_data( unsigned char data)
{
    __delay_ms(1);
    LCD_PORTB = (data & 0xf0);
    RS = 1;
    Strobe();
    LCD_PORTB = (data << 4 );
    RS = 1;
    Strobe();
}

or shorter

void LCD_data( unsigned char data)
{
    __delay_ms(1);
    LCD_PORTB = (data & 0xf0) | 1;
    Strobe();
    LCD_PORTB = (data << 4 ) | 1;
    Strobe();
}

 

[thannara123]

You should try to understand what you are doing here.

RS is also located in PORTB, so the correct LCD_DATA function could like this

void LCD_data( unsigned char data)
{
    __delay_ms(1);
    LCD_PORTB = (data & 0xf0);
    RS = 1;
    Strobe();
    LCD_PORTB = (data << 4 );
    RS = 1;
    Strobe();
}

or shorter

void LCD_data( unsigned char data)
{
    __delay_ms(1);
    LCD_PORTB = (data & 0xf0) | 1;
    Strobe();
    LCD_PORTB = (data << 4 ) | 1;
    Strobe();
}

changed as you said but not worked sir ,

 

[betwixt]

Show us the whole code again now you have implemented the changes we suggested.

Brian.

 

[thannara123]

Show us the whole code again now you have implemented the changes we suggested.

Brian.

#pragma config FOSC = XT         // Oscillator Selection bits (XT oscillator)
#pragma config WDTE = OFF       // Watchdog Timer Enable bit (WDT disabled)
#pragma config PWRTE = OFF      // Power-up Timer Enable bit (PWRT disabled)
#pragma config BOREN = OFF      // Brown-out Reset Enable bit (BOR disabled)
#pragma config LVP = ON         // Low-Voltage (Single-Supply) In-Circuit Serial Programming Enable bit (RB3/PGM pin has PGM function; low-voltage programming enabled)
#pragma config CPD = OFF        // Data EEPROM Memory Code Protection bit (Data EEPROM code protection off)
#pragma config WRT = OFF        // Flash Program Memory Write Enable bits (Write protection off; all program memory may be written to by EECON control)
#pragma config CP = OFF         // Flash Program Memory Code Protection bit (Code protection off)
#include <xc.h>
#define _XTAL_FREQ 4000000



#define RS  PORTBbits.RB0
#define EN  PORTBbits.RB1

void Strobe (void)
{
    EN = 1;
    __delay_us(2);
     EN = 0; 
    
}
void LCD_cmd( unsigned char cmd)
{ 
    PORTB = 0x00;
    PORTB = (cmd & 0xf0) ; 
     RS = 0;
    Strobe();     
    PORTB = (cmd << 4 )&0xf0;
    Strobe(); 
      
}
void LCD_data( unsigned char data)
{   PORTB = 0x00;
    PORTB = (data & 0xf0) | 1;
    Strobe();   
    PORTB = (data << 4 ) | 1;
    Strobe();
    
}
void LCD_init()
{
    __delay_ms(20);
     LCD_cmd(0x38); 
     __delay_ms(4);
     LCD_cmd(0x38);
    __delay_ms(2);
    LCD_cmd(0x28);    /* 4bit mode */
    LCD_cmd(0x28);    /* Initialization of 16X2 LCD in 4bit mode */
    
    LCD_cmd(0x0C);    /* Display ON Cursor OFF */
    LCD_cmd(0x06);    /* Auto Increment cursor */
    
}
void string(const char *ptr)
{
    while (*ptr)
    {
        LCD_data(*ptr++);
    }
}

     void main()
    {
       TRISB =0;
       PORTB = 0X00;
      
      
      
       LCD_init();
       while(1)
       {
      
     string("HELLO WORLD");
      // LINE2;
       string("Testing)");
      //LCD_data(1);
       }
               return ;
}

Also change the circuit as said

 

[KlausST]

Hi,

PORTB = 0x00;
PORTB = (data & 0xf0) | 1;

could give a race condition problem due to pipelining

better do:

PORTB = 0x00;
NOP;
PORTB = (data & 0xf0) | 1;

*****

PORTB = (data & 0xf0) | 1;
    Strobe();   
    PORTB = (data << 4 ) | 1;
    Strobe();

results in a very narrow EN=0, because in STROBE function there is no delay after EN=0

better use:

void Strobe (void)
{
    EN = 1;
    __delay_us(2);
     EN = 0;
    __delay_us(2);    
}

Klaus

 

[andre_luis]

Didn't you note you are issuing an 8bit mode configuration command to the LCD whereas the actual connections are for 4 bits only ?

---

Code C - [expand]
1
LCD_cmd(0x38);

---

 

[danadakk]

Might be prudent to confirm you comply to the 44780 controller timing :

More info in datasheet, attached. Also there are knockoff 44780 chips, confirm what
your module has to make sure you are working with correct datasheet.


Regards, Dana.

 

[betwixt]

There is still a potential problem with writing to PORTB. When you use:

PORTB = (cmd & 0xf0) ;
PORTB = (cmd << 4 )&0xf0;

you reset the lower four bits of PORTB which drives EN and RS low.

Personally I #define all the pins to the LCD, including the data pins and then set/reset them individually. It avoids any clashes when writing to the port because each bit is controlled without changing the others and as a bonus you can use any pin on any port to connect to the LCD. It does take a few extra instructions but given the delays are there anyway it doesn't slow things down significantly.

something like this:

#define LCD_D0 RB4
#define LCD_D1 RB5
#define LCD_D2 RB6
#define LCD_D3 RB7

LCD_write(char data)
{
if(data & 0x01) LCD_D0 = 1 else LCD_D0 = 0;
if(data & 0x02) LCD_D1 = 1 else LCD_D1 = 0;
if(data & 0x04) LCD_D2 = 1 else LCD_D2 = 0;
if(data & 0x08) LCD_D3 = 1 else LCD_D3 = 0;
}

then pass the commands/data to the LCD_Write routine in the lower 4 bits. By changing the defines you can swap any port pins. It is also quite easy to expand the routine to write 8 bit data.

Brian.