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Whats wrong with this LCD command FUNCTION?

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Naumanpak

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Experts,

I have this lcd command function but cannot initialize the lcd in 4 bit mode. 8 bit was done without any problems but am struggling to initialize LCD in 4 bit mode.

Code: 
void lcd_command(unsigned char command)
{
        rw=0;
        delay_ms(1);
        rs=1;

        PORTB  = PORTB&0x0F;
        PORTB  = PORTB|(command&0xF0);
        enable=1;
        delay_ms(1);
        enable=0;
        
        PORTB  = PORTB&0x0F;
        PORTB  = PORTB|((command<<4)&(0xF0));
        enable=1;
        delay_ms(1);
        enable=0;
}

where,
rs PORTB.RB2
rw PORTB.RB1
enable PORTB.RB0
and D7-D4 are connected to RB&-RB4


thanks
 

Hi,

First of all, RS should be equal to 0 for command transfer.
Other part is seems to be ok. Try with keeping rs=0.

NIKS
 

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    Naumanpak

    Points: 2
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thanks NIKS, it should be '0' but still doesnt works?

Forgot to mention, Lcd pins D3-D0 are grounded.
 

I don't know C but I believe this LCD manual would help you.
Go to page 7 and look at the table, row - Function Set. D4 (8/4)

Yes, when RS is 0, it means it's in Command mode, where you can use the table in the manual.

Basically, RS+RW should be 0 --> Set D4 as 1 , only, not F --> Toggle Enable...

Then you should be in 4 bit nibble mode, then you need to configure your LCD depending what kind of LCD you have.

Grounding D0-D3 does not make any difference for me in my circuit, good practice I suppose? But I don't think it is required since the LCD will ignore it once in 4 bit mode.

Hope it helps.
 

    N

    Naumanpak

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If I am not wrong, you have to write 0010xxxx (D7-D0) to initialize it to 4 bit mode. You could try writing it directly (i.e PORTX = 0010xxxx) before using your lcd_command for other intializations.
It worked for me.
 

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    Naumanpak

    Points: 2
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